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Guest
Anonymous Poster
lruehl@nrlfcu.org
Aug 8, 2007, 6:52 AM
Post #1 of 2
(2179 views)
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Engine Overheating
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OK So I have a 2001 Cadillac Deville with 95,000 miles on it. Recently the engine started overheating and a mechanic told me it was because of a blown head gasket. I got a second opnion and was told that if the car is not leaking coolent and if I didn't have to add coolent (I never had to add coolent and the car is not leaking coolent.) then it probably wasn't a blown head gasket but a smaller problem. This mechanic says he replace the water pump and the head gasket (don't know if this is true because he didn't charge me anything) and the engine was still overheating. He siad it is a cracked engine block that is causing the overheating but again there is no coolent leak. I need some advice, could there be another proble that could be causing the engine to overheat? I would really like to not have to replace the engine beacuse honestly I don't the $9,000 it would cost to do that. Any advice would be helpful. THANKS!
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 8, 2007, 8:37 AM
Post #2 of 2
(2177 views)
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A head gasket can be difficult to diagnose. A cracked block could be tricky also. Either way there would be evidence somewhere. You said your overheat and don't lose coolant. Hmmm? That's inconsistant with either of those problems.
You said you got a new water pump and a head gasket (you would do both head gaskets?!?!?) and no charge?? I don't think so.
A head gasket with no leaks could be burning it unseen. At an extememly small rate you wouldn't have much of a problem. If it was a tad more of a leak you would notice loss of coolant which you are not. It could leak into the oil which would become like a milk shake and be too full. Worth checking. Head gasket can let combustion gasses into oil crankase or cooling system and with the cooling system would overheat as would be letting bubbles of air into system and quickly pressurize cooling system and would usually spill out coolant out of recovery tank and if it could draw back coolant when it cooled down (lack of slight vacuum in cooling system when cooling off would prevent recovery of coolant) but then you would notice loss of coolant or at least the recovery tank getting way too full quickly and system pressurizing before it warms up.
Head gaskets can leak anything they seal in either direction. They allow for compression, oil to pass to heads, coolant to pass to heads, crankcase air to and from valve covers to about oil in oil pan etc.
A cracked block would be leaking something in the wrong place too. Engine probably wouldn't run well.
You are overheating so let's get to the basics. You have a "water cooled" engine as most vehicles do and the principles are the same. With everything properly working, coolant full, engine running..... The water pump is working even with a cold engine. It keeps all the coolant in the engine close to the same temperature to prevent hot spots and this constant mixing within the engine is done by the by-pass system. This allow for even engine temp and informs the thermostat of the overall engine temp and it will open at a prescribed temp, usually around 190F if will start, and the already working water pump allow the coolant to go to radiator to be cooled and returned to engine. So...... If radiator didn't cool the coolant the coolant then returns this coolant too hot to help and your engine would overheat. A stuck closed thermostat could prevent coolant from flowing thru radiator, a clogged radiator could prevent the flow thru it, lack of fan for the radiator could prevent enough cooling of the coolant, the by-pass system which can use the heater core may not allow proper mixing of coolant in the engine and thus the thermostat get incorrect information and may not open on time and you can overheat. Lack of a thermostat can prevent the by-pass system to work properly as coolant is constantly being cooled but only in one part of the engine and can overheat there and be late to let you know by you gauge and that is damaging because if your engine get real hot at one end and stays cool at another it really stresses the gaskets and the block and heads.
Coolant is constantly running thru the engine, sometimes the heater core, the intake manifold, and the heads.
I don't think I missed anything but this is basics off the top of my head. Any mechanic who choses to work on engines should have a basic understanding of the cooling system. If a mechanic doesn't want to deal with engines at all there are plenty of other things in a vehicle to keep you busy, Tires, brakes, suspension, electrical assesories, alarm systems, stereo etc. Even auto body repair that includes collision repair involves the basics of overall operation as radiators get smashed and so on. Techs generally chose areas of expertise now as there are more different types of cars within a few model years than there were parts in a whole car a long time ago.
Sorry for the dissertation but you need a mechanic with a good grip on the principles of how it works and the ability to diagnose what part of all this isn't working. Best to do this before the damage as you stated could result in the need for a whole new engine,
T
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