Quote:
Originally Posted by Frank Lee
Re: "cooling off": I've heard it's more about letting the exhaust valves cool a bit so they don't warp, and on old turbos, to let them cool a bit so they don't bake the oil in the bearing.
Never heard of a head warping/cracking due to temp variation from front to rear... that's just bizarre (I think unlikely- is the rear of the engine compartment 200 degrees hotter than the front? The engine is LIQUID cooled right?) and I'd be pretty PO'd at Volvo if that was true.
Here we are: Volvo B230 Headgasket Repair
That sounds much closer to the truth. |
What happens to temperature of water in cylinder head when you switch off engine, does it increase or decrease?
No when you have negative temps you can get that 200 degrees difference quite easily as -20 blowing over 50mph to other end when other end is surrounded by relatively calm positive temperature air (measured 50C difference from surrounding air temperature, add windchill to front of engine that removes heat), when you stop and shut off engine water is not circulating and is nearly or at boiling point at rear of head while front is something like hand warm. I had always trouble to keep heat up with that thing.
That means there being lot of different expanding and compression happening at different ends and you can end up with a crack or warp if thing boils at rear of engine, evening out temps no more than 30s-1min is needed and I do that much more pleasantly than face alternative.
edit: B230 is four cylinder petrol engine, D24 is 6 cylinder diesel used in Volvo, they share nothing same between them.