2003 Buick Rendezvoux overheating randomly

[NebraskaVern]

My Buick 2003 Rendezvoux has intermittent overhearing issues. I have replaced the water pump, radiator, thermostat, water temp sender, and the radiator cap. This was done by my local mechanic.

I have ordered another thermostat, a "fail safe" one that he suggested.
He recently replaced one of the coils for the 2-5 cylinder that was not firing. Drove fine, went to town about 11 mile away and back. My wife drove it to 2 meetings, no issues.
We decided to drive it to South Haven for grocery shopping, but about 4 miles from home, on the interstate, the bell went off alerting to overheating. She pulled over, and I examined under the hood. Pulled up the flap on the engine coolant reservoir and it started to gush out. The radiator cap and area was cool to the touch. We waited and then drove home, getting off at the next exit, and took the back roads if we had to stop again
When we got home I popped the hood and engine radiator cap was cool to the touch, but the fans were running for the radiator. It started to get hot when we drove down our driveway.

Afterwards, next day I checked the coolant reservoir and it is normal. Took off the radiator cap and radiator is full of coolant.
The hose between the reservoir and radiator seems to be very soft and pliable. Could it be collapsing when trying to draw in coolant?

Am baffled as to why this happens, and it is intermittent.
Any clues?

 

[Boomer]

Really sounds like a faulty thermostat. Are you sure it is installed correctly?

 

[eljefino]

You've got an air bubble behind the thermostat. If you drill a tiny (8") hole in the top of the flange it'll help burp the air out.

As to why the air bubble, you might be in the beginning stages of head gasket failure. You could gimp it along for a surprising time with the thermostat mod.

The thermostat (and water pump) are the only failures that would lead to a cold radiator with overheating engine. Did you happen to notice if you had amazing heat? Great heat= good water pump.

 

[NebraskaVern]

Thanks for the quick replies. As far as thermostat installed correctly, I am sure Robert made sure. He has been doing auto mechanic work for many years. Even built racing engines. There is one in his shop now he is working on.

The small hole sounds like a plan. Robert replaced the water pump about a year ago. Replaced the thermostat in Dec of 2022, but a stuck thermostat is always a possibility as it is mechanical. He told me on the new one to order a "Fail Safe" that will allow some coolant. Also he suggested to put a pan of water on and boil, and dip the new thermostat in the water to see if it opens up. If it does not, it is defective and needs to be sent back.

Many times it runs great, no overheating. My Daughter used to drive it a lot. She had experienced overheating as well as me, and we stopped the motor and let it cool down before driving home to park it. I figured that perhaps the engine temp sensor was faulty, so bought a new one and Robert replaced it.
I look at the oil, and it is clean (Robert changed a few hundred miles ago), and the coolant reservoir does not show any signs of oil or other issues. Seems like it pretty much HAS to be the thermostat, as the radiator cap was cool to touch. which is very odd given that we just drove it.

Wouldn't a head gasket issue occurr all the time for overheating? It has been many months since this has reared it's head again, and I would think a head gasket leak would lead to coolant in the cylinder(s).

 

[nwjones18]

Was the first thermostat installed OEM? If it wasn't GM Genuine I'd forget the failsafe and get that.. And I let all mine open in hot water before I install, I've been burned multiple times with new thermostats that wouldn't open (motorad, which is pretty much all you can get aftermarket these days)

Amazon.com

 

[Warstud]

I have ordered another thermostat, a "fail safe" one that he suggested.

I've used two of those fail safe t-stats and both made my cars run cold . Just get an OEM one .

 

[Nick1994]

My mom had an ‘03 Rendezvous years ago that had bad overheating random issues. Even after a thermostat replacement as well.

My mechanic figured out it was the head gasket that was bad, putting exhaust gases into the radiator. Constant bubble that couldn’t be burped.

 

[GMBoy]

My mom had an ‘03 Rendezvous years ago that had bad overheating random issues. Even after a thermostat replacement as well.

My mechanic figured out it was the head gasket that was bad, putting exhaust gases into the radiator. Constant bubble that couldn’t be burped.

Yep I agree with the head gasket theory having seen this a few times....especially if it has the 3.4 V6.

 

[The_Eric]

I also agree with the possibility of a head gasket issue - it is not uncommon for these engines. My wife had a car with the 3.1 (little brother to the 3.4) that was doing the same thing. Once the bubble was burped out, it ran normally for quite some time before it failed for good.

You can put all the thermostats you want in it, but you'll still have overheating issues. Generally a quick way to tell is if you've lost heat at the vents. A stuck stat will keep everything behind it hot (which includes the heater). If you have a head gasket issue, then combustion gasses will cause an air lock and keep the pump from circulating the coolant - and because no coolant is being circulated, you wont have heat in the cabin.

 

[mattd]

Head gasket failure on those are fairly common. Sounds like with your history that this may be the case.

 

[John Galt]

 

[Marcozi]

The installation of aftermarket cooling system parts is strictly verboten.

 

[NebraskaVern]

Thank you ALL for all the great replies!
I used to be in here as Nebraskan, but it was so long back I could not remember my password, and doing a reset would not work as I had a totally different email back then. So, I created the account of NebraskaVern and as soon as the Admin gets it figured out I will revert back to my old username of "Nebraskan". Not being kicked out, but just limiting my username to just one. Now that he and I have figured out my old email I managed to reset my password and can now log in as "Nebraskan".
Just wanted you all to know. Really, really great advice. Was hoping for something less expensive, but EXPERIENCE is a wonderful tool in the shop!
Vern

 

[someonesomewhere]

I've used two of those fail safe t-stats and both made my cars run cold . Just get an OEM one .

Those Fail-Safe stats are trash. They always 'fail' and when they do, they lock open (that's the fail safe, no overheating). Waste of money.

Also, agree with everyone about this potentially being a hg issue if it's a 3.1/3.4. We lost a 95 Camaro to these issues. Body was trash so it wasn't worth fixing.

 

[Nebraskan]

The video, showing a plumbing issue is rather intriguing. Might be worth a look as it should not cost nearly as much as doing a full head gasket replacement. Crux of the video is putting in a flow restriction in the manifold heating plumbing. You all would have to see the video, as I may not be describing it well.

 

[John Galt]

I have a 2002 Buick Rendezvous with a 3400 engine as in the video. I Replaced the water pump and belt three weeks ago (awful rattle - now that’s gone) and the original OEM radiator cap. Both NAPA sourced since I can walk to NAPA and I like to patronize the store to keep it open. it took a few tries to bleed the system of air but I think I’ve got that set. But I think I have a fan issue - fan does not turn on unless I turn on the AC then one fan runs. There is a YouTube video where the guy isolates the issue to the fan temperature switch Located right next to the thermostat housing. That’s next on my try this next list.

 

[wtd]

I don't use anything but OEM thermostats and radiator caps unless I just can't get one. It definitely could be a head gasket issue. Do you lose coolant in the overflow bottle?

 

[Warstud]

My Buick 2003 Rendezvoux has intermittent overhearing issues. I have replaced the water pump, radiator, thermostat, water temp sender, and the radiator cap. This was done by my local mechanic.

I have ordered another thermostat, a "fail safe" one that he suggested.

Maybe under the circumstances he recommends using a fail safe t-stat so this issue doesnt make things worse

 

[LouC]

Look for bubbling and/or a sooty discharge in the coolant recovery tank. This is a clear sign of exhaust gas getting into the coolant vis a leaky head gasket…common on Subaru EJ 2.5s we had it happen twice.

 

[super20dan]

our subie ej25 did same thing x2