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Re: Do bolts need retightening after a new cylinder head change?
Posted: Tue Sep 16, 2008 1:31 pm
by Simon Jones
mikeonb4c wrote:But, is it possible tha oil might leak from the head into the bores (from cracked head or gasket problem) when stationary, causing blue smoke on start up? I've no idea but the thought occurred
When the engine is off, I believe its usually worn valve stem seals that cause oil to get into the bores. Worn piston rings will tend to allow oil to get in when the engine is running.
When the engine is running, the compression is very high (to cause the diesel to self-combust) & the resultant explosion will tend to find its way through any tiny leaks in the system. In other words, the tendancy will always be for leaks to travel from the combustion chambers into the oil or coolant, rather the the other way around. If the coolant system becomes over-pressurised, then once the engine is off, the water can be forced back into the cylinders which will produce the puff of white smoke at start up. To get continous white smoke, I think there would need to be a significant problem for the water to be getting in all the time.
That's what I 'fink anyway
Re: Do bolts need retightening after a new cylinder head change?
Posted: Tue Sep 16, 2008 6:17 pm
by mikeonb4c
Simon Jones wrote:mikeonb4c wrote:But, is it possible tha oil might leak from the head into the bores (from cracked head or gasket problem) when stationary, causing blue smoke on start up? I've no idea but the thought occurred
When the engine is off, I believe its usually worn valve stem seals that cause oil to get into the bores. Worn piston rings will tend to allow oil to get in when the engine is running.
When the engine is running, the compression is very high (to cause the diesel to self-combust) & the resultant explosion will tend to find its way through any tiny leaks in the system. In other words, the tendancy will always be for leaks to travel from the combustion chambers into the oil or coolant, rather the the other way around. If the coolant system becomes over-pressurised, then once the engine is off, the water can be forced back into the cylinders which will produce the puff of white smoke at start up. To get continous white smoke, I think there would need to be a significant problem for the water to be getting in all the time.
That's what I 'fink anyway
All makes sense to me. Well, fingers crossed things may not ALL be pointing to a head/gasket problem then
