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Originally Posted by franklynb
I'm perhaps not as blind as you think.
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Blind as in not having a diagnosis strategy and just randomly taking things apart.
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Originally Posted by franklynb
The transmission had partially failed ; |
This means nothing to the over heat situation.
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Originally Posted by franklynb
and the engine had shown exhaust guide wear from a leakdown test and chain measurement done several months ago.
Doing a proper leakdown --with known leaking valve guides-- is a bit of a crap shoot, yes?
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A leak down test won't diagnose " leaking " ( ? ) valve guides.
Valve guides can only wear , and for all practical purposes , not leak. If they are worn they need to be measured with the head off with plug gauges or a dial indicator put against the valve stem for measurement. If by " leaking valve guides" , you mean " leaking valve stem seals / valve guide seals" A leak down test won't identify them either since a leak down test won't apply any pressure to the guides.
For completeness, a leakdown test is where one has both valves closed and air is pumped into the cylinder through the glow plug / injector or spark plug hole. Leakdown is expressed as a percentage. During a leak down test it is important to identify _where_ the air is being lost.
Most engines with any amount of time on them will have slightly leaky exhaust valves ( air out the tail pipe ) , slight leakage here is no cause for concern.
Mid time engines will have air leaking past the rings, this isn't any great cause for concern if oil usage isn't excessive.
Very high time engines will have leaking intake valves, this becomes a power issue because it allows combustion gasses to enter the intake manifold giving the effect of full time exhaust gas recirculation.
>>> If a head gasket fails or a head cracks from combustion to coolant, leak down air will enter the cooling system. It is good practice to remove the rad cap when doing a leakdown, any bubbles / geyser of coolant is a indicator that the cylinder you are testing is where the leak is. If this had been done prior to removing the head you would have known for sure there was a combustion / coolant leak in a specific cylinder.
Now, there are very isolated instances where a leak down won't identify loss of coolant into the exhaust but, identifying the source is very easy when the head is taken off. An example is a early 80's Ford Escort that would crack the floor of the exhaust port allowing coolant to escape in to the exhaust.
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Originally Posted by franklynb
And the "threaded boss" is just that; NOT the dowel pin next to it, which is also rusted. And its the only boss with rust, as previously stated.
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If there was a coolant leak to the head bolt or dowel pin, the coolant would have nowhere to go once the miniscule volume was filed.
( BTW, the yellow arrow in the head pic is pointing to a different cylinder than the block pic, I am referencing the block pic for the dowel pin. )
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Originally Posted by franklynb
In particular, I am concerned by the SPALLED tracks between the cylinder sealing area, the dowel pin perimeter and the boss
... which might/might not show combustion gas mixing with something else, like coolant from the port to the left of the boss --
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There does not appear to be a direct path from combustion to the coolant passage. However, if a pre tear down leak down test showed leakage to coolant in that cylinder _and_ the head tested crack free, I'd call the gasket bad in that location. And you would not go through the " what if ? " , " is this the bad part ? " series of gyrations.
Quote:
Originally Posted by franklynb
-- IF I'm not "blind". Sarcasm noted.
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I'd call it living up to your avatar sig line. .. .