Stat problem?

2004 GP GT 63000kms on it...winter time here...temp gauge shows that car only warms up to the 1/4 mark not halfway...but if i let it idle for a while like in a drive thru, when the waterpump isnt pumping, the heat does go up to halfway but only then, should i be worried?

when the waterpump isnt pumping

err, just to be sure, the waterpump runs 100% of the time the engine is running unless you have shredded an accessory drive belt.

I had similar problems, 2000 GTP where the temp gage would barely lift off its lower peg. I had some heat but not like i do now...which is after replacing the thermostat and the ECT sensor. Also my engine oil temp is running slightly warmer than before with roughly the same ambient so I have to conclude that the thermostat was bad.

However...the pair of parts are about 1-1/2" from each other and the coolant has to be drained to repair either...so I elected to just do both in one shot, refill and bleed the coolant 1 time and be done and sure the problem was fixed. IIRC total cost for both was approx $30USD at rockauto prices.

sounds stupid but where is the stat in a 2004?, and it is easy to replace write?...any more tips?

Follow the upper radiator hose back towards the engine (close to/under the intake air ductwork)

The tstat is under the cast-aluminum water outlet (bleeder screw on top).

Two 10mm-hex bolts IIRC.

The new tstat has its own "gasket" which is a round rubber ring. (not a flat paper/fiber gasket).

The ECT sensor is right under the tstat in the intake lower. I think 15mm box wrench will do it, have to clear the crossover pipe and do some careful wrenching.

I did the bleed procedure about 5x just to make sure I had it done as best as possible. I use 2 wadded up paper towels, stuff this in ahead of time where the bleed screw opening is located, then use a 7mm box wrench to crack the bleeder screw when the engine is warmed up and idling. If it spits air then you need some more tries. When the towels get soaked, I let it idle some more and bleed some more. Then allow to cool and do again on another day to allow the engine to pull in more coolant (add via radiator neck if grossly low).

I will try this, but can't i just run it till coolant bleeds out from bleeder valve once ? and what is the ect? What kinda Coolant is best, that Dexron

ECT (sensor) = engine coolant temp sensor which feeds signal to both the PCM and the IP (needle on the dash).

I would use Dex-Cool instead of Dexron (which is transmission fluid) :) You want the orange-colored coolant. Mix 50-50 with distilled water, or you can buy premixed to 50/50 for a premium price at most auto parts stores. Note both of the above chemicals are formulations that GM "designs" and validates for use in their vehicles. GM licenses the formulations to other chemical manufacturers. (IOW Prestone manufacturers and sells Dex-cool coolant in a Prestone bottle) So you don't have to buy this from the dealer...just look for the "GM tradename" on the bottle to assure compatibility.

You can do the bleeding anyway you like, that's just how I did it...wanted to make sure it was done right and didn't cause an overheat.

2004 GP GT 63000kms on it...winter time here...temp gauge shows that car only warms up to the 1/4 mark not halfway...but if i let it idle for a while like in a drive thru, when the waterpump isnt pumping, the heat does go up to halfway but only then, should i be worried?
What you should do is calculate what temperature the gauge is showing when it is "1/4 mark". Mine barely gets above the "1/4 mark" when driving around and always has been that way since new. As for it getting up to 1/2 "like in drive thru", I think this is normal too. Once it gets that hot, the fans kick on and blow the heat off, since you are not moving. I don't see any reason to change anything, based on the evidence presented.

The temp guage fluctuation you described in your first post is normal. If you have no other issues like loss of heater output or any coolant smell coming from the car then there is nothing wrong.

The temp guage fluctuation you described in your first post is normal. If you have no other issues like loss of heater output or any coolant smell coming from the car then there is nothing wrong.
ok thanx alot bro...its was alot warmer here yesterday and everything was like it was last spring, just guess they run colder in the winter....i grabs the top hose and it was hot to touch right away so i know its working good, also my level is up, but i have that 5 year stuff and dont believe i should wait that long to change it, should i change it after 2 years, get a flush done? and can the shop bleed the valve if i ask?

What you should do is calculate what temperature the gauge is showing when it is "1/4 mark". Mine barely gets above the "1/4 mark" when driving around and always has been that way since new. As for it getting up to 1/2 "like in drive thru", I think this is normal too. Once it gets that hot, the fans kick on and blow the heat off, since you are not moving. I don't see any reason to change anything, based on the evidence presented.
thanks man!

I'm still thinking this over. I sat at a drive-up/take-away tonight in 50F ambient for a half hour at idle and my coolant temp gage didn't budge from the normal "run zone".

However, if the PCM thinks the coolant temp is too low you'll get an SES code. Without that, and if you can achieve 4th gear TCC locked you probably are OK.

The outlet-side thermostat location on the 3800 variants drives "slugs" of coolant which quickly change temperature as you drive down the road and lead to the IP gage movement. Some improvement was made with a tapered-throat tstat design which is sort of a "soft start" when it comes to the amount of flow allowed with a small tstat opening. Conversely, an inlet-side tstat location equalizes jacket temperatures considerably better but requires a massive bypass passage to prevent waterpump cavitation.