Head gasket?

BX Tech talk
Post Reply
User avatar
toddao
BXpat
Posts: 2833
Joined: Fri Jan 12, 2007 5:01 pm
Location: The Hegau

Head gasket?

Post by toddao »

The previous owner of the TRD believed the head gasket needed replacement. He is a mechanic but I couldn't follow his reasoning owing to my poor German. But before I accept his diagnosis and embark on the unpleasant task, how can I be convinced this is the problem?
None of the symptons - that I am aware of are present : no white smoke or coolant in the exhaust, both water and oil are normal condition with no souping. I can't see any visable leaking. The only unusual thing is that water squirts out of the over-flow though it isn't over-filled or hot.
I haven't ran it up to temperature yet ( to check over-heating) only idling for a few minutes as it's inside. Is compression testing an option and how to do this with diesels as I'm only familiar with the plug option? It's got very low mileage but is this irrelevant with gasket failure?
Thankyou
Todd


this yellow writing is really hard to read
jeremy
Over 2k
Posts: 2112
Joined: Fri Jul 01, 2005 2:58 am
Location: Hampshire UK

Post by jeremy »

Look at it this way:

If it isn't overfilled and squirts water out of the filler - that water is propelled by something - which is a gas.

Its possible that the gas could be steam from intense local overheating - but while steam expands enormously when its generated - but it condenses when it cools.

Combustion gases however do not - so the question is when it cools is it under vacuum or not? If there's still residual pressure then it must be combustion gases.

Bleeding? - not really - while air in the system may cause local overheating and a breakdown in circulation - it will not cause an increase in gas in the system - so the pressure at the next cold startup should be the same as the last.

Compression testing diesels is difficult - and some use a system of measuring the current consumed by the starter as a measure of the engine's resistance to turning. You could operate the stop lever on the pump and rotate the engine and see what you can hear.

These engines start well on 3 cylinders which means that a slightly weak cylinder would not necessarily be noticed. You might find if you loosened the injector pipes in turn that it would start with the suspect one loosened and not the others.

Be careful not to get high pressure fuel sprayed on your skin - it can penetrate and cause serious health problem.
Stewart (oily!)
1K Away
Posts: 1604
Joined: Wed May 18, 2005 6:23 pm
Location: North Wales

Post by Stewart (oily!) »

Loosening injector pipes is not an option, pressure lost from one seems to stop all of them, if its blowing water out of a cold engine then its pretty certain that the HG is gone, often without the other symptoms of mixing oil/water, with the engine cold, start it and hold the top hose, if the hose pressurises within a couple of minutes and may even apparently pulse as you squeeze it then its a fair bet that the gasket is done for, do not run the engine in this condition for long as the pressure can damage other components, the good news is that its a straightforward job on the old N/A diesel engine. good luck
Stewart
TZD 19 TD one of the few
Xantia Td estate, going soft
Post Reply