Maybe the heater core or radiator is plugged somewhere causing the pressure build up

 

I'd do some more diagnostics (pressure test the system with a actual pressure tester OR run a flush kit that will help dislodge debris) before just chucking money at a radiator. Just me, I'm a little apprehensize to do that, but I have seen clogged radiators. One test of that is watch the radiator hoses when someone else starts the car. If one sucks in, you have a clog for sure.

I don't think he knows what brand elbows he was using, but as I stated earlier, the guys on the Bonneville forum this year were having LOTS of failures with the Dorman elbows (the o-rings are not able to hold the pressure of the cooling system). Heck, I had a Dorman elbow blow out on me first week the Monte was out. I blame myself, I got too anxious and did not completely bleed the cooling system. It had a massive air pocket and that could have been enough over pressure.

This is why he needs to ensure he has NO air pocket. The idea of the t-stat is another good thing to look at if it has not already been replaced (could be opening late these days causing extra heat OR he has a air pocket still causing a large temp reading as hot air reads differently then hot coolant on those probes).

 

The old ones where dormans, the GM elbows are considerably better made.

Checked & confirmed no air pockets or bubbles coming out of the bleeder at least 5 times. No visible leaks

After driving around a couple of blocks the temp gauge gets up to and under the 1st notch after half. I have not witnessed it get any higher, but as soon as it does this I pull into my driveway, either try bleeding it again or I've just sat there and waited ~3-5 minutes for it to get back to the half way mark.

I did have the thermostat changed on 3/22/11..

We have a compression kit, Ill have to check into this monday.

 

As previously mentioned, ambient temperature will have an effect on how hot a vehicle runs. With 90° temps expect to see it run hotter than normal. When we had 80°+ temps last summer my Monte ran a couple of ticks higher than normal but never overheated. Are you running a 50/50 water/coolant mixture?

 

It has been in the 90's and very humid...

it's finally raining!!! Hopefully it was just because of the heat

 

i had an issue with this last year, turned out to be that my heater core was plugged tight causing a lack of coolant flow and high pressure... a couple bottles of CLR, a bucket, and an air compressor got mine all cleaned out and flowing well again

also ONLY use the GM elbows, or a pair of metal elbows, they won't let you down near as fast

 

I've never been able to find metal elbows (aftermarket or on a forum). Know something we don't??? Care to share???

 

Update on this:

TStat has been replaced... seemed to help some.

So my temp will only get over half if I really step on the gas (after it warms up)... something like getting over a lane going from 60-70mph.

With the AC on it runs about 2 notches over half...

For the most part of my drives it will stay under half... but then it goes up (sometimes it will go down right away) other times it just stays there longer than it should before going down (5+minutes).

I'm thinking of changing out the coolant and trans fluid (been replaced one) & maybe a new radiator.
(car has 120k on it)

Any other ideas???

 

Before you go crazy, find someone with a scan tool, plug into the ODB-II port under the dash, pull up the temp sensor. Get real numbers. Instrument panels can sometimes have issues with them and not show the real deal. The other thing is, the outside ambient temp plays into what the car reads.

 

Weather does have an effect on coolant temperature, I'd say it's a 10-20 degree range. I have a 180 degree tstat in my car, and it normally runs 177-185. On super hot days, and in stop and go traffic, it has gotten up to 203. (Stock is 195)

Your issue with the bursting coolant elbows is definitely too much pressure, either a gasket is overlapping somewhere it shouldn't, or you have a blockage (heater core or radiator, as mentioned). Don't ever discount a line being blocked like one that goes to the tranny.

Good luck.