high temp problems buick rendevous

[chanfish]

My wife rendevous temp gauge shoots up sitting in traffic. it goes from 1/4 to 3/4 and even higher with these high temps..had it in twice to firestone and spent $340 and no fix yet..they did thermostat and backflush but again with high temps and sitting in traffic it shoots back up. they said they thought the fans were working ok..any ideas would be great....

[Scott K]

Are the cooling fans coming on?

[Jeremy airjer W]

Year? I'm guessing a 3.4 liter and around 60-80k miles?

If so have them check for a head gasket failure. There are several ways to do this. My favorite is with a four gas analyzer. If its really bad you will be able to smell hydrocarbons in the coolant reservoir after driving it.

The other thing I see quite a bit is the build up of debris in between the radiator and the condenser. Sand and cottonwood like to settle on the cooling fins of the radiator. A good thorough blowing from the engine side of the radiator with shop air will usually do the trick.

The other possibility is that the gauge is inaccurate at slightly higher temps. A scan tool can be used to see if this is the case.

Really common for the head gaskets to go out on these especially in the SUV/Mini vans.

[chanfish]

fans are working..140K. would headgasket failure would cause temps to jump up in traffic and high heat but otherwise run cool? would it be then losing fluid over time? thanks for the quick reply. its back down at the shop right now.

[BartmanMN]

how's the water pump?

[chanfish]

no issues with waterpump that i know of..the tech i talked to mentioned that the fans may have two speeds and perhaps the second speed is not kicking in. i told her to check the coolant level. if its down, it must be going somewhere, ie headgasket. if not then we have something else..the auto runs really good otherwise but with these high temps the heat gauge is shooting up in traffic etc..thanks

[chanfish]

they say no on the headgasket. continuing to flush the radiator which they already did before. now they are saying new radiator if this dont work..

[delcecchi]

If it were a clogged radiator, wouldn't the temp go up more when the engine is working hard, like at highway speed? But if it were junk clogging the airflow, then highway speed would push more air and stopped would be worse.

I think Jeremy, who knows way more about cars than I ever will, had a good suggestion. I am not so sure about the firestone guys.

[chanfish]

well they just called and say they backflushed it again and while its not overheating the guage shoots up to 3/4 still. oh and by the way they said the oil was 3 quarts low. I said that was impossible cause no leaks and no oily exhaust. he said he thought maybe someone had drained oil by mistake! the car had never used oil before and now it burns that much overnite?? he says now it might be guage..i am going down and getting my vehicle before they do anymore damage to it..then on to the gm dealer..what a misadventure....get what you pay for but in this case i have been paying for nothing...btw this was goodyear not firestone. my bad...too bad cause the guy helping was a nice guy but i dont think their mechanics know what they are doing. they looked younger than my 19 yr old son!!

[Jeremy airjer W]

How often do you check the oil?

When was the last oil change?

It is not uncommon for these engines to burn oil. In fact I have solved a few oil consumption issues with new lower intake gaskets. Speaking of those, is it possible that they are starting to leak coolant externally? Did anyone check the coolant level in the radiator before any work was done?

It is not that hard to compare the gauge with the computer reading with a scan tool. A GM will not turn on the fans until the coolant is about 220 degrees. The center of the gauge is about 200 degrees so it is possible for the gauge to read high ion a hot day, especially with the A/C on.

I would still be curious if there is a build up of debris in front of the radiator.

[Whoaru99]

To Jeremy's point, are you sure there's even a problem? The temp gauge in my older (91) Camaro moves up quite a bit when you go from driving to stopping in traffic on a hot day, yet it has never overheated.

It bothered me for the longest time but just as soon as I figured it was on it's way to going Old Faithful, the fans kick in and the temp hovers at that higher level until I start driving again.

[chanfish]

well i am driving her rendevous and shes driving my truck...now driving it myself the guage still surges to 3/4 but i didnt notice it doing it only sitting in traffic. it just did it going down the road. these high temps definitely are bringing this out..we take that car in for oil changes every 3K so this oil loss surprises me..airjer--when this all started i suspected low coolant but she took it in to them and thats when the whole backflushes, thermostat, and now oil thing started. the care did overheat initially which is what started this. now the temps go to 3/4 but not overheat-light comes on deal..they now think its the gauge but it surges up and goes down so i am not sure..i do appreciate everyone's assistance..they didnt say anything about debris etc. pretty much a city car...

[fish_eat_sleep]

is the chevy 3.1L v6 in the same engine family? my brother has a 2001 malibu that was doing the same thing at idle sitting in traffic, and sometimes while getting off the freeway. well anyway the cooling fan wasn't coming on when it should after the motor warms up. the mechanic took apart the fan and reassembled it (without any new parts) and i haven't seen any odd temp gauge movement since. he said it could have been a loose or bad connection at some sort of relay or switch. kind of a freak thing they couldn't diagnose.

[chanfish]

It's FIXED!!

[chanfish]

I took it to gm dealer. service guy diagnosed right away..yes it was the external fins and condenser that needed to flushed and cleaned. (airjer you were right on that)..problem is they had to remove the radiator to get at the engine side of it. the bay floor looked like a sandbox when they got done. They had an escalade with over 300k miles in this morning with the same exact problem.. now i can move on to going out fishing!! thanks everyone....

[Jeremy airjer W]