[T2] Power loss in 4th

[jules]

On Wed, Jan 20, 2016 at 4:14 PM, Avocado Tom Tarka <avocadotom at gmail.com>
wrote:

> Jules,
>
> As I mentioned in my previous email: the cooling fan intake is not
> obstructed.
>
>
Cool. (literally) how about those flaps under the shroud that are
opened/closed by the thermostat. Do you have the thermo? is it installed?
adjusted correctly? does it open completely when the engine warms up, and
are the flaps open completely when the thermo is open?



> My valves have been adjusted to spec and have not tightened or gone out of
> spec in the last 50-75 miles of testing I've done.
>
>
depending on your driving style and conditions that might not be enough to
tell (especially in the winter). it seems like an odd strategy to
potentially cause damage to a head, to possibly burn it out by driving a
vehicle with an issue to see if it overheats - when one could diagnose the
individual components in the cooling system in the driveway, with less
risk, less work, and less chance of damage. Looking at the damage caused
after the fact can be useful for determining why a catastrophic failure
happened - But - it's much less useful as a diagnostic tool while the
engine is still operational - especially if you want to keep it that way.

Tom I think we'd love to see you get up and running, hopefully without
doing further damage, please check your flaps so we can definitively
eliminate it as a potential cause of your issue.


there are many other factors that can make an ACVW engine run hot, these
factors are additive, even multiplicative, so it may be a combination of
many small factors, adding up to a larger issue. other potential cooling
issue you might not have considered:
    thermo jammed, flaps stuck, flaps obstructed or completely missing.
These are required - even if you plan to have the thermo always open - you
MUST have the flaps in place - they don't just open and close - they direct
the cooling air flow directionally towards the hot parts of the heads
    loose fan shroud or large gaps in the tinwork can cause large cooling
air leaks and cooling loss. tape up the gaps, get the tinwork tight and
sealed up. Seal up all the no longer used holes in the tinwork. make sure
you've got the tube that the accelerator cable travels trough that's
inserted into the tinwork, preferably with grommets so it makes a good
tight air seal. Every little leak adds up
    The round seals/grommets around the tubes that go from fan shroud to
your heater boxes often missing, also, if equipped there should be a
pre-heated air intake to your air cleaner that comes up from around the
muffler into the air intake - there should be a grommet here, and, if this
intake passage is missing, as it most often is, it should be sealed up. any
air leaks here can cause hot air from around the muffler, or exhaust gasses
themselves. to be drawn  into the cooling air stream.
    Cracked/Broken heat exchangers, damaged exhaust gaskets - can cause hot
exhaust gases to be drawn into your cooling air or even worse, right
through the heating system int the cabin
    Heat exchangers are "open" and disconnected - you're passing air
through the heat exchangers then venting them into the air beneath the
vehicle where they can get drawn right back into the engine's cooling air
stream.
    The cooling air intake "scoops" could be blocked or obstructed by
something. (Do you use the extra space in the engine compartment for
storage, or extra features - is it blocking cooling air flow?
    A previous owner has installed an aftermarket oil cooler that's
installed in the cooling air flow. ie, an external engine oil cooler has
been installed in the engine compartment and is dumping heat into the
cooling air.
    Missing main engine seal around the engine in the engine bay, can cause
hot exhaust or heated air near the exhaust to be pulled into the cooling,
    a missing or damaged decklid seal can make it hard for the cooling fan
to work when the vehicle is moving at speed.
    the grommets/seals around the intake preheater tube are
missing/damaged. the preheat tube could be compromised, dumping hot exhaust
gasses into the intake (not impossible, but unlikely)
   etc, etc, etc

and perhaps the most common (or at least very common) cause of overheating
on the type 1 engine: a loose fan belt

then there are the factors that aren't at all related to the cooling system
    driver is pushing the vehicle too hard
    timing is too far advanced
    driving into strong head-winds
    there's too much stuff on the roof or driver driving with the pop-top
open
    brake drag
    bearing replacement(s) needed
    tires all well underinflated
    it's too hot out, etc... etc

the flaps are still the 'feature' designed to help your engine get hot
fast, and are, in my opinion, the most likely culprit for your unexplained
overheating.

peace
jules
'75. 78 westies,
troy ny