Hydraulic Lifters and Type IV Pushrod Tube Seals

by John Anderson

Hydraulic Lifters can be Adjusted Warm!

Despite popular belief, it is not necessary to adjust hydraulic lifters stone cold. In fact, there are times and means where you purposely strive for this not to be the case. When you adjust a hydraulic lifter, you are adjusting it to contact plus somewhere between 1 and 2 turns of the rocker arm adjuster screw. That screw is a special fine pitch 10mm, but still is good for 1mm per turn (.040"). Taking an average of the information available, you will be adjusting to .060" past contact.

Consider why on a solid lifter car you must adjust the lifters stone cold. It is so you aren't adjusting them when valves are warm and "stretched." Though I'm also a mechanical engineer, I'm not going to bore you with numbers. But think for a second about what you know. We adjust those solids to .006" gap, which implies that an exhaust valve will NEVER stretch more than .006" in use. Otherwise, we would be holding it open all the time (even when on the backside of the cam lobe, and that is very conservative). These valves aren't going to probably stretch more than a few thousandths of an inch.

So we know a valve isn't going to stretch more than .006" and that VW over the years has proffered an adjustment range from .040" to .080" past contact on the hydraulic lifters. That valve can be as hot as it can get and you still have a 3 to 4 time slush factor either way of a "perfect" adjustment. So you see, hydraulics don't have to be cold for an adjustment. The only thing to watch out for with the warm engine/one that has just been run is to avoid burning yourself (!).

Identifying Hydraulic Lifters

You just bought a beautiful lime green and rust '78 Westy and when you start her in the mornings you get something between a tapping to pounding sound from the old engine that changes with engine speed. You remember what the old bug (or '71 and earlier bus) sounded like with loose valves? This sounds the same but even louder (even up to a hard pounding beat). You think you got them hydraulic lifters...

A can tell if you have hydraulic lifters in a couple ways. First, pull either valve cover. Take a "mini Mag" flashlight and look up a pushrod tube around the rocker arm. If that little pushrod is only about the size of a big round (3/8") pencil all the way end to end and looks steel (probably brown and oily), chances are there are still hydraulic lifters in there. If instead, right behind the tip, behind the rocker arm, the pushrod steps out to a big, ugly aluminum rod (probably closer to 1/2" diameter and probably more silver in color) chances are you have solid lifters in the block. If they are all currently adjusted to somewhere in the .004-.008" range you can guess pretty much for sure.

By the book, only GD, GE, or CV blocks came from VW with hydraulics (but only '78 and '79 GD blocks). All Vanagon CV blocks came with hydraulics. Be aware that hydraulics could have found their way into any T4 block over the years--hopefully along with an hydraulic cam and the steel pushrods. If you see steel pushrods and if when you rotate each cylinder to TDC and try to get a feeler between the valve tip and rocker screw there isn't a gap, you indeed have hydraulics. This is a good thing--but why that infernal pounding?!

Air in the Lifters

The hydraulic lifter lets the valve ride on a cushion of oil, always maintaining perfect preload and contact on the cam but not so much (oil pressure balances the spring pressure) that it holds the valve open. Assume your '78 shows an actual 120k or so on the original engine (though they can get noisy much earlier if not driven, not maintained, etc). As these accumulate time, the lifter parts lose their tolerances. Overnight, or after setting, the oil inside them leaks out, air leaks in and when you start up, the air has to find its way out. Imagine the lifter as a syringe of water, but with the needle end closed and flat against the cam, the plunger against the pushrod. Now that water inside is instead being pressurized constantly to 40 psi or so (oil pressure) from a little hole in the side of the syringe. If a big bubble of air leaks in so it is only half water and half air inside, and if everything is closed off (by the external oil pressure when you start the car) the air is trapped. When you push on the plunger the air compresses and the plunger can collapse easily some distance before a balance is achieved.

Oil can't be squeezed. Air can be, therefore it is not good to have air in your lifter. You can check for this if you have noise. Go along with a big screwdriver and try to push on the bottom end of the rocker shafts, right in line with the pushrod. Do this when the cylinder is near or at TDC and the valve train is not loaded (though many of the valves will be unloaded at once so give em all a quick push). The rocker shaft is knurled right where you press so the screwdriver won't slip. When you press (and I mean a good hard press) there should be no movement at all. Chances are some of them will be "soft" when you press them. Maybe they will move in less than 1/16" of an inch feeling spongy. Those have air, but are probably OK. Then there will be a couple real offenders. Those you will be able to shove a good bit. These definitely have a lot of air in them and little oil. You are basically just compressing the big spring in the lifter. So we have hydraulic lifters with air in them. What do we do?

The questions we must ask are: Does this happen every day? Does the rapping stop after 10-15 minutes driving? If you drive the bus everyday does it stop even faster? My first opinion: if you know the engine hasn't been fooled with and the bus hasn't been driven in a few weeks, change the oil to something light (10W30), put on a new filter, and sit there in the drive and rev it up and down for 15-20 minutes, staying in the 2000-2500 rpm range. Get it good and warm but don't rev it too high. If the bus has sat for a few months or even a few weeks and begins to quiet out, then subsequently quiets out each morning after even up to as much as 10 minutes, and isn't banging really loud: don't worry.

I parked my old '78 on a sideways slope for 8 months then fired her up. It always had 2 dying lifters that pounded for 1/2 an hour (and I mean pounded). Make sure all the rocker shaft nuts are torqued correctly and be happy. NEVER, EVER, use Quaker State oil with VW hydraulic lifters. Generally, I run the oil weight VW recommends. In my climate that means 10W30 winters (but only if it stays cold else maybe some 15W40) and 20W50 in the summer. VW is very conservative about oil. They recommend thicker stuff than most manufacturers. Use a good oil and filter and change it every 3-5000 miles. If you run the proper weight oil it won't cause you any noise or trouble. I use Castrol GTX or Shell Rotella exclusively. I can often run the Rotella 15W40 diesel weight oil year round in a camper that doesn't get everyday use.

Still Making Noise?

So it still pounds? If you didn't know any better, you'd be tempted to adjust the valves. There are 3 much possible solutions:

1. Bleeding the Lifters
2. Additives and Purging
3. Special Adjustment Procedure (a compromise, as proffered by Mark Steven's and others)


This is the hardest, most labor intensive "solution" and it most likely won't solve your noise problem! You can refer to the relevant section in the Bentley (official VW service manual) for the "bench bleeding" procedure, for what it's worth. To do this you must pull the valve covers, pull the springs retaining the pushrod tubes, pull the rocker arms, pull the pushrods, pull the pushrod tubes, then pull the lifters (discouraged yet?!).

Replacing the pushrod tube seals

Admittedly, this can be a good thing to do if you want to replace pushrod tube seals anyway. Replacing these seals correctly can be an adventure in itself. In short: don't use RTV. O-rings work on clean, lubricated surfaces by compression. That tube of blue, orange, red, or black goo won't last-- you'll be back again facing the same leak in a few months, doubling your labor and aggravation. After removing the aforementioned parts, immaculately clean the areas surrounding each lifter bore. Ideally, you should do this the day prior when you pulled the under pushrod tins (if present). It's also a good idea to soak bottom of the engine block with degreaser in advance. Scrub the block around the tubes with a toothbrush, hose it off with hot water, then let it set to cool and dry overnight.

After that, clean out each bore carefully with kerosene and paper towels (as many as it takes). Clean the bigger part of the bore where the pushrod tube O-ring has been riding and you make sure nothing is up in the machined lifter bore itself. Pushing a scrap of towel back into the top of the lifter and using a toothbrush on the bore where the o-ring sits is good. The towel prevents debris from settling back in the bore.

Do the same to the bores over on the heads. Install Viton o-rings with silicone grease (or at least oil) and those tubes won't leak again. Verify the tubes are not dented where the o-ring sits--that will cause a leak. Also, if you are experiencing blowby (gases that slip past the piston rings, pressurizing the crankcase) nothing will stop the leaking.

Back to Bleeding the Lifters

Now that the bore is spotless, we can pull the lifters. Use a good 2lb magnetic parts "picker upper", or catch the lip of the lifter with a pointy right angle pick. If you choose the latter technique be very careful not to slip and scratch the bore. If everything is clean, a magnet should get them out, but you might have to work them back and forth a bit.

Pull all of them and keep them in order. If you're pulling them all, you can store them in an egg carton with numbered holes (#1I, #1E, #2I, #2E, etc.) or do them one at a time. If you're only doing the ones that feel soft, just be sure you somehow keep track so that a lifter goes back in its correct bore.

Now is a good time to inspect the cam. The T4 cam wears badly. Let's assume power and compression are off, and the heads are newish on an old bottom end. Look down the bores at the toe (top area) of one of the lobes on the cam (at least one is going to be facing you down a hole). Is it smooth and even or is there a 1/16" dip in the center? If here is a healthy dip, your compression has very likely been low and power is down. In this case, your bottom end's days are numbered. Assuming there is over 100k on the engine and you didn't buy it from meticulous owner who changed the oil every 3000 miles, be aware that your power will continue to wane. Expect a $1500 bill sometime in the next 25k miles. The Type IV bottom end is rock solid as far as the crank and rods go, but the cams wear.

Now we'll disassemble, bleed, and reassemble the lifters one at a time. Remember to return each of them to their numbered bins.

Inspection and Disassembling the Lifter

You'll need:

Take a lifter and inspect it. Bentley says to push the socket with your thumb, I say use the pushrod (even one off your Type IV engine for now). Lean on it with all your might. If it doesn't move, or barely moves, return it to its spot in the numbered tray. If the socket sinks noticeably and easily, while holding it down (not really necessary) remove the circlip with your needle nose pliers or the 2 screwdrivers. Note: unless you have 10 or 20 used lifters sitting in a box like me, do this in a clean area on clean newspaper (kitchen table is good). If that circlip flies off and hides itself and you want to drive the bus tomorrow, you better have a metal detector (ask me how I know!).

Take out the socket, plunger (with check ball, spring and retainer), big spring, etc. The valve retainer will snap off the plunger with finger pressure, revealing the ball and little spring. Let it all soak in the can of kerosene for a few minutes, then scrub all the parts with a toothbrush or Q-tips. Lay everything out to dry on a paper towel. Everything should be clean and shiny. Blow out the body with air if available, else make sure all the kerosene is gone with a paper towel or Q-tips and blow the lint off with your mouth. If anything looks terribly worn, scratched, or scored, you should replace it. However, you'll probably find most of even the real soft ones look brand new inside. That is because the wear and tolerances we are dealing with are minute.

Reassembly and Bleeding

If you've been refering to the Bentley manual, you'll notice at this stage it becomes particularly useless. They expect you to have a press and jump through hoops keeping the body immersed in a pan of oil while pressing. Ironically, the Vanagon Bentley carries over this foolish procedure from the '68-'79 Bentley, but also has (in section 15.24) the far better procedure for the wasserboxer lifters...which can also be used for the air cooled lifters!! Needless to say, we will be following the better instructions for the wasserboxer.

You need a vice. A big C clamp will do (though I've never tried it this way). A small vice is fine, just the length of the lifter plus an inch or so. You also need about an inch of that bug pushrod, or the inch long 5/16" bolt with the tip filed semi-circular and smoothly sanded.

Take some SAE40 oil and lube all the parts, then put the little spring in the check valve retainer. Sit the little ball on the spring and clip the assembly to the bottom of the plunger, making sure the ball stays centered on the spring. Drop the big spring in the body of the lifter and take the SAE40 oil and fill the body of the lifter until it overflows. Immediately drop in the assembled plunger/check valve assembly. Oil will swish out the hole in the side of the body and over the top. As you put it in, put a pick or the tip of the paper clip in the hole to push the little ball down, so as the plunger slides in, oil and any air under the plunger come out the valve and the plunger sinks nicely into the oil filled body. Push it down with your fingers as far as you can. Now top off the body if it has flowed out and drop in the pushrod socket. You won't be able to get this in all the way--that is what the vice is for.

Immediately take the lifter to the vice, but put a pad between the lifter face and the vice (aluminum soft jaws are great if you have them). Hold the lifter there with the little hole in the side of the body facing up while you hold it all together. Use your smoothed bolt or 1" section of pushrod in the socket and close the vice, compressing the socket as shown in the Vanagon Bentley figure 15-493. Do this just far enough to expose the groove for the circlip. Oil will ooze out the body side hole. Install the circlip. Take it all out, store with the face down, and test it again with thumb pressure or the pushrod. It should be rock solid. Repeat this as many times as needed on the lifters that need it.


Reinstall the lifters, pushrod tubes, pushrods, rockers, retainer springs, everything in order. Back all the adjuster screws out maybe 3 or so turns. If you don't know valve adjustment basics, you may refer to the information in Muir's Idiot book, the Bentley, or even the Haynes manual.

Go to each cylinder one at a time and set it to TDC for adjustment. If you've backed the screw out 3 turns or so, both rockers on that screw should rattle freely. Bentley says back it all the way until it is flush with the rocker. That is fine as well, but make sure the pushrod does not slip out of the socket on either end at the lifter or in the rocker. With them just loose this won't happen--double check by looking down the pushrod with the mini Mag Lite. The pushrod should spin if it is loose in between the two sockets. If it does fall out on the inside end and rest against the lifter somewhere else, you will notice because the pushrod will be too far out, making the adjuster screw contact way before all the others do (probably before it is even hardly out past the rocker.)

Also check when you push with the screwdriver on the pushrod end of the rocker: it should now be dead solid. You might have a time limit here. Even with 40 weight oil, and not having run or warmed up, your newly bled lifter could leak in air overnight just sitting there on its side, so install them immediately before adjusting. Also, install the lifters with the little holes initially up.

The rockers are loose and that cylinder is at TDC. Now, with the tension off, is a good time check the torque on the rocker shaft nuts. Watch while you run each screw in till it just touches the valve. A good way is by rocking it with one hand (tap, tap, tap) while you turn. When it just touches: no tap. Then turn it 1, 1.5, or 2 complete more turns. VW initially said 2, some say 1, I compromise at 1.5 turns. Do both on that cylinder, tighten the adjusting lock nuts. There's no need to be fussy about holding the screw while tightening, just make sure the screw doesn't turn while you cinch the nut (unlikely).

Move to the next cylinder, set it at TDC, repeat, etc. You have just correctly adjusted your lifters by the book. They are going to stay that way with that thick oil in them. But the bad news is, when you run it the first time and it sits a day, the noise will be back! At least you have verified that a lifter is badly worn. Perhaps you should replace the real soft ones, or, if they quiet down after 5-10 minutes, live happily knowing they are set correctly. The bright side is the pushrod tubes don't leak anymore, and maybe you know the cam is worn and should be passing the Bus along or thinking about a rebuild.


If even after an oil change the valves still tap mercilessly and don't stop after 20 minutes of revving in the 2000-2500 rpm range, pull the covers and verify they are soft. Consider that if the engine is in the 100k mile range and there is much burnt oil in the rocker boxes, it might not be long for life. Perhaps it has just sat a long time and the lifters are immersed in dirty oil. In this case they need to be flushed.

You could try an STP "wonder" product, CD-2?, Warner or other aromatic solvents claiming to solve all your lifter problems. It might work...or it might knock so much debris loose you will regret it the rest of your engine's short life! If it is a new engine with lower miles I might be inclined to toss a can of "wonder" liquid in. But I'd do it a couple of days before an oil change and if it doesn't help, change the oil.

Next option is to flush with thin oil. (SAE10 if you can find it, Dexron Automatic Transmission Fluid otherwise). Somewhere between 50/50 10W30 to ATF or just straight ATF if you are feeling manly. Be forewarned, this is risky and potentially engine life threatening, especially if too much stuff breaks loose or if things get too hot. A new oil filter should catch most stuff, but... I've gone the straight ATF route. For you, maybe the 50/50 is a better, more conservative bet.

If at any time you see the oil light come on--STOP IMMEDIATELY--cool down, and go back to regular oil. Even with normally worn components, a 10 minute run with RPMs up should not cause a 150k mile engine to have oil pressure problems. If you notice pressure problems, you have other mechanical issues to attend to: worn pump, extreme bottom end wear, overheating, etc.

Start the engine and as before, run it up to 2000-2500 rpm, this time for about 10 minutes. Keep the rpm's moving around a bit, let it cool for 30 minutes, then repeat. Repeat maybe 4-5 times with good, long cool downs and stop if the lifters stop tapping. If by trial number 5 nothing is changed: Stop, change back to oil, consider replacing suspect lifters as in step 1.

If the noise at idle did go away, stop, and add new, quality oil and filter. Keep it changed (every 3000 miles) and start the bus every day and let it run 15 minutes or so. This can be a great trick to clean things out. It can also be fatal if done badly or if you are unlucky. If your bottom end is loose already, nothing fixes extreme wear and bad maintenance. I've done this to clean out a few vans, and you may do it wisely and at your own risk. I also killed a GTI engine this way that sucked too much debris up the filter screen. I've heard professional mechanics recommend the straight ATF route, but again, this is at your own risk.


You may use this procedure if your lifters are noisy for 5-10 minutes then quiet down to no more than a minor tapping at idle (or when you let up on the throttle suddenly after acceleration). Do this if you yearn for something "scientific minded", but don't want to pull the lifters. This is the best thing to do when you just get a "new to you" bus. First, check for the soft lifters as before, then do the following. Adjust all the valves to .006" just like a solid lifter engine. This is a bit tricky. Be sure when you adjust a soft one that the feeler gauge isn't just compressing the lifter. Go to TDC, back the screws out until they don't touch, and gently rest a finger against the pushrod end of the rocker holding it against the lifter (but not compressing the soft lifter) then adjust the other end to the .006 gap. Repeat for all valves at the appropriate TDC for each cylinder.

Start the engine and let her run a minute or 2 at 2000-2500 rpm. It will be very loud. Maybe it will quiet a bit. Stop the engine, pop the valve covers, turn to a cylinder and see if the previously soft lifters are now hard. If so, immediately close the gap (Which may already be gone if a soft one pumped up. In that case open the gap then close to just contact). Adjust to 1.5 turns past contact as detailed previously. The valves are warm so don't burn yourself.

Had you checked them all before and all 8 were solid, you might find when the time came for the adjustment procedure (adjust, turn the engine, adjust, etc.) by the time you get to the last 4 they might already be soft again! My old '78 was this way: the bad ones would only hold pressure for maybe a minute or 2--had to work fast on them. This is no real problem. Just do the one side first, then put the valve covers on, start it for another 2 minutes, go do the other side. This is a practical way to get them pumped up and assure they are in good adjustment. If you adjust to 1.5 past contact ON A SOLIDLY PUMPED LIFTER you endanger nothing in the valve train and the lifters have plenty of slop, plus they seem to pump up better running loose. If they refused to pump solid you need to adjust to about a turn or so past contact to roughly where it was before you started. With contact being ascertained as before by gently holding the rocker on the pushrod, you might need to consider bench bleeding or eventually replacing the lifter, or with luck it might just go away.

Some play is acceptable, but if you can push the rocker down an 1/8" you have problems. You can try to adjust all the way round and perhaps all will be right. But you'll likely find the next morning nothing will have changed. So keep the oil clean, and don't worry if they tap for even as much as 15 minutes or more if the bus sits for a month or so. Basically, live with it, and don't worry so much unless things are really banging around back there.

Again, you may want to consider flushing with ATF--it can work miracles and stop the noise, or it could be a $1500 solution! You make the choice. For the first 15 minutes most days you should have nothing more than extremely minor tapping and valve noise from a hydraulic lifter VW van. perhaps you can have noise from one or two lifters that sounds like a properly adjusted mechanical lifter bus, no more. The length of time it taps depends on the oil, angle it was parked on, how long it has been since run, etc. But a faint persistent tapping from one now and then that won't purge is nothing to get upset about--chances are it will come and go.

Someone on the Type2 mailing list mentioned that their valves seats had been cut to the point where the rocker shafts rested on the retainer and compressed the valve. That isn't right. I don't think a Type IV seat installed at the correct height could be cut so far (correctly, without cutting out of the seat) that the valve is that deep into the rocker box. But this is just speculation. Shimming the rockers is about all you could do--but I think spring tension would be way low in this case.

Something I recently noticed: the 1.7 style rockers with 8mm adjusting screws perhaps have a different ratio and are not interchangeable with 2.0 rockers (or maybe the rocker shafts are set at a slightly different height?) Perhaps the real problem were the 1.7 heads rebuilt for the 2.0 engine, or perhaps the difference was my imagination (?). Or perhaps the early, solid lifter 1.7 components and the 2.0 hydraulic valve train isn't strictly interchangeable. Regardless, something is incorrect in that situation. There should always be adequate clearance between the rocker arm and the retainer.

It is important that the adjuster screws stick out past the face of the rockers for the entire distance where they are turned down and probably a couple of threads. If anything (with machined valve tips) they should be sticking out more. Generally speaking, for all the prior procedures, it is a good bet that ALL 8 ADJUSTER SCREWS best be turned in about the same amount if everything is correct. If one is drastically different from the others, something is wrong: the pushrod is not seated correctly, the rocker shaft isn't tightened, you adjusted at the wrong time, or a variation on that theme.

The tips of all the valves should be level. Determine this with the rockers removed and a straight edge across the tips. If there is a minute difference, the tips might've been machined or there might be a small variance in the valve seats--this is acceptible. However, if one of the valves is sticking out over 1/16" when all the rocker shafts are off, you have the beginning of seat recession. If that cylinder's compression measures at 90 psi or so, you'll soon need a new set of heads or an engine rebuild. Heads will run with a seat pounded 1/8" into the head, but not well. In that case, all the adjustment in the world isn't going to help you.

A final note: if you do have a couple very bad lifters and they disturb you (even the 10 minute tapping) replace them. They only cost about $10 from Bus Depot, more from RMMW. This might not be a great idea though since the lifter isn't guaranteed to be a great match for the hardness of the cam. Also, some of the replacement lifters have a smaller hole in the side of the body than the original had and might be less inclined to purge air. If you do install a new, replacement lifter, make sure it was properly bench bled solid before installation.

As I've implied, all these problems tend to show on old, high mileage vans. By the time you have 125k miles on a poorly maintained Type IV engine, chances are that the cam is beginning to wear with the hydraulic lifters, and the heads are soon to go, etc. Replacing some things may buy you time but you must carefully consider everything you do. For instance, $500 in heads on an engine whose cam is failing doesn't make a lot of sense. Perhaps you should save for a new engine.

A lot of vans get sold this way. A novice bus buyer overpays for a bus ($2500 for a $1000 bus), then 6 months later has $600 heads installed (often badly by non-VW mechanic who leaves big gaps in the tin). Six months or a year passes and the engine is dead and the novice sells the bus at a loss, unaware of the dynamics at play. Be smart, trust your own good judgement and do your research. Read a copy of Tom Wilson's "How to Rebuild a Volkswagen Air Cooled Engine" book and read it even if you never intend to rebuild your own engine. Do it so you can speak intelligently to a shop. At least run the checks Muir describes before ever buying a bus in the first place. Bob Donalds also has some sensible words on this subject. You might want to look at his thoughts on hydraulic lifters and cams in the Type IV in his articles section.

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