Question about 2003 Buick Rendezvous

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2003 buick rendezvous engine temp keeps moving from hot to cold

Engine temp will bounce from cold to hot(red line). I've replaced the thermostat and coolant temp sensor and am still having problems. I may or may not get any heat in the passenger compartment. I attempted to check to see if there were any compression gases mixed in with the coolant using a detection leak it. However, I wasn't able to verify because coolant kept bubbling out of the radiator and mixing with the detection fluid. I'll be replacing the water pump next. Any other suggestions as to next step or am I out of luck and will need to replace the head gasket?

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  • Jeff Western
    Jeff Western Jan 14, 2013

    After checking everything again, it appears to be leaking head gasket. I picked up a kit to check for exhaust fumes in the radiator. I wasn't able to test it as the instructions showed because coolant kept filling up the tester.

    I also noticed that when the engine was running hot, the coolant overflow was full and I could see air/exhaust bubbles.

    May final determination is that the exhaust fumes pushes out the coolant which is why the heater blows out cold air. The engine pushed enough exhaust out of the system for the coolant to feed back in to the coolant system, cooling the engine and providing heat inside.

    I'm in the process of tearing down the engine now. It's slow going because I have an unheated garage and the temp has dropped down into single digits. I'll provide an update once the project is completed.



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Don't change the pump or anything else until you have carried out the basic checks to establish what seems to follow all the usual symptoms of a head gasket failure. Remove all the plugs and carry out a cylinder compression test. They should all be within 5% of each other. Its likely you will have 2 readings next to each other that are low or nil. Note if any coolant is spat from any cylinder when cranking. Then, with the coolant topped off, pressure test the water system with the appropriate test kit and see if the pressure holds. My guess is it won't. Don't guess at the problem, carry out a sequence of tests and usually all will be revealed. Coolant gases can be carried out after running.

Posted on Apr 17, 2017


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Posted on Jan 02, 2017

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SOURCE: My 2002 buick rendezvous is overheating. The water

first check to make sure the cooling system is not air bound,takes a while to bleed off the air,try this and get back to me Thanks Ray

Posted on Nov 13, 2009

  • 382 Answers

SOURCE: 03 Buick Rendezvous Overheating

If the top hose is hot and the bottom is cold, your definitely not getting circulation. You,ve already done alot of work to this vehicle so you have pretty much answered your own question. About the only thing left is the heater core. Of course, I dont want to be the one to tell you it is definitely the heater core because obviously I am not looking at the vehicle. But If i was a betting man, thats where my money would be.

Posted on Dec 14, 2009

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SOURCE: Replaced the water pump on


Posted on Sep 08, 2010

  • 1702 Answers

SOURCE: I have a 2004 Buick Rendezvous that runs hot.

cylinder head gaskets, or cracked cylinder heads, this is a bad problem with the 3400 engine, so bad that we keep a set of heads in stock at the shop.....SORRY

Posted on Nov 14, 2010

  • 1 Answer

SOURCE: how do you replace a coolant temp sensor on a 2003

where is the filter on an 03 rendazvous

Posted on Dec 10, 2010

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Try this:
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