2004 Pontiac GP running on hot side

[clarkflower]

Hi

My 2004 Pontiac Grand Prix 90k has started to run on the hot side (hotter than I'm used to) while sitting stopped in traffic. It is very hot here. It does not get to the red but on the gauge shown here I'm getting close. About 5/8 with 3/4 being red. Normally I don't run above 7/16 maybe 1/2 at a red light and then it drops to 5/16. Now it's only dropping to 1/2 when I start running although it seenms to be a bit erratic. Drops to 1/2-7/16 and quickly pops back to 9/16, then back to 1/2 at a steady 50 mph.

http://gtcarlot.com/data/Pontiac/Grand+Prix/2004/1555158/Gauges-44231528.html GP Temp

expected it to be low on fluid but it was full. Both fans run. No anti freeze in the oil.
It did this 6 months ago after I bought the car. I added fluid and its been fine since till now.

Any thoughts?

 

[Boomer]

Are the fins in the radiator full of debris? Water pump OK? Thermostat failing?

 

[clarkflower]

Thanks
No
Do water pumps fail like that or do they just go completely?
Could be.

 

[Trav]

I would get a new OE thermostat and Citric acid flush the system. As the other poster mention flush the radiator fins from behind.
Check the temp with a scan tool. If its a GTP it already has the thicker radiator, which is a good upgrade for the SE and GT.

 

[clarkflower]

Thanks Trav..Its a GT but it looks clean.

 

[Trav]

Water pumps on these are not known to come apart, the bearings fail sure but its a noticeable and usually noisy fail.
A GTP radiator (OE) would be a great upgrade to this cars cooling system.
I got one (OE Modene made in Canada) of ebay one time for $50 because the guy thought it was too thick and wouldn't fit and sold it. GM used 10mm spacers from the factory to put the thinner radiators in the SE and GT, just leave them out and it fits perfectly.

Look at Rock for the delco OE for the GTP it is about $150 and well worth it, Delco was OE in 04, Modene the earlier ones. Same deal toss the spacers to fit. Temps will drop considerably, the part # ACDELCO 21555

 

[Audios]

Its possible that the vanes are worn on the pump, so its effectively flowing less coolant at idle than it should be. Id take a look at the pump, or you can try a coolant additive like water wetter to give it a little extra boost in the cooling power.

 

[bullwinkle]

A cheap IR gun could be a good investment here-is it possible that the sender & gauge are incorrect? Shooting the thermostat housing when hot usually will give you an idea.

 

[sprite1741]

Did you check the coolant in the engine or just the overflow tank? I have seen engines low on coolant but still reading normal in the plastic tank. Means a leak somewhere. My V8 GP has been running in the middle in traffic but drops slightly when back to speed. I had a GTP before, I seem to remember on the V6 there was an cooling system air bleeder on it. Could have some trapped air. I remember fighting it once after a coolant change. Had an air lock. Might check for air in the engine.

 

[clarkflower]

Thanks Trav... As you know Im on SS now so I'm trying to keep some reserve in case I need intake manifold gaskets done.

I just did the thermostat..

 

[Rand]

Originally Posted By: clarkflower
Thanks Trav... As you know Im on SS now so I'm trying to keep some reserve in case I need intake manifold gaskets done.

I just did the thermostat..


just did the thermostat? was that after or before it started getting hotter?

did you use an OE part? most aftermarket are junk.

Possible air in the system?

 

[Chris142]

Flush the bugs out of the core. Feel for cold spots if you can get your fingers in there.

 

[clarkflower]

Thanks. Because it was so hot I only checked it in the expansion tank and it was a little bit low in the actual radiator this morning.

Where it was low before, i’m thinking I may have a small water leak somewhere but nothing visible.
The guy at the GM dealer thought I might need intake manifold gasket’s because he said he saw oil.

I did the thermostat this morning after I was running hot and I’ve been out most of the mornning. It seems fine but I also added coolant to the radiator.
Seems I lost 1/4 gallon in 5 months?

 

[maxdustington]

"Widetrack"

 

[JamesBond]

I would make sure that the cap is clean and holding correct pressure and that the hose from the radiator to the overflow tank is clear and is tightly sealed at both ends.

If your radiator is low and the overflow tank is normal the radiator could pe pushing out water as it warms up as usual but sucking in air as it cools down due to a bad cap or hose.

 

[Trav]

Originally Posted By: clarkflower
Thanks Trav... As you know Im on SS now so I'm trying to keep some reserve in case I need intake manifold gaskets done.

I just did the thermostat..


Some of these cars had a coolant level sensor in the radiator some didn't depending on the trim, the GT usually do.
If yours has it (it will be right under the top transmission line and you have no low fluid warning the radiator it full enough and the overflow bottle will take care of the rest just keep that at the full mark hot a few cycles.

There is a bleed nipple, you might want to crack that a couple of times, engine off and engine on. If the GM mechanic suspect a leak you would be doing yourself a big favor by doing it preemptively, once they start ever so small it can get much worse fast with no warning and do a lot of damage, you may or may not see the leak externally.

Use GM aluminum frame gaskets only with the green port seals, yes they are better than the Fel Pro knock offs. GM spent over a decade to get these right and since these were introduced they have been stellar.
When you do this job you want to change the WP, tensioner (OE Parts) and use aluminum elbows with GM o rings (the o rings that come with the aftermarket elbows are a poor fit and prone to leaks. Fel Pro blue silicone VC gaskets are great and last 10 yrs minimum (those are the oldest of many I have still in service leak free) as is their upper plenum gasket, use them with confidence.

Use Hylomar M on the elbow o rings and end seal gasket joints with a thin layer under and over the manifold end seals, do this and this engine will be a tight as a drum for longer than you can ever imagine keeping it. Its an afternoon job, really.
If you really want to put the cherry on top, flush it out and refill with JD Coolguard II, that all I use in these and its fantastic.

I hope you find something in this post helpful.

 

[clarkflower]

Is there a good way to tell if the intake manifold gasket has gone bad?

 

[wag123]

Originally Posted By: Trav
Water pumps on these are not known to come apart, the bearings fail sure but its a noticeable and usually noisy fail.
A GTP radiator (OE) would be a great upgrade to this cars cooling system.
I got one (OE Modene made in Canada) of ebay one time for $50 because the guy thought it was too thick and wouldn't fit and sold it. GM used 10mm spacers from the factory to put the thinner radiators in the SE and GT, just leave them out and it fits perfectly.
Look at Rock for the delco OE for the GTP it is about $150 and well worth it, Delco was OE in 04, Modene the earlier ones. Same deal toss the spacers to fit. Temps will drop considerably, the part # ACDELCO 21555

+1
Borough a cooling system pressure tester and test the cooling system to make sure it is holding pressure. If it does, replace the radiator. It is 14 years old now and part of the core is likely plugged. Even a new non-HD radiator is only about $100, hardly an exorbitant expenditure. Replace the radiator cap while you are at it.

 

[Trav]

Originally Posted By: clarkflower
Is there a good way to tell if the intake manifold gasket has gone bad?


UOA. I do them all the time on these engines even after LIM replacement a few times to insure the repair was successful.

 

[clinebarger]

You've gotten some really nice technical info from Trav, But I will throw my 2 cents in as well.....


Your cooling fans run in series when low speed operation is commanded (Both run at half speed)
They run in parallel when high speed operation is commanded (Both run at full speed)

IF Cooling Fan Relay #1 fails.....You will have NO low speed operation & only the right cooling fan will work when High Speed operation is commanded.

By the time the right fan comes on....Engine temps will be around 225-230 degrees. The one fan will probably be enough to maintain but not recover at a stand still in hot weather.

This is a common failure across the entire GM passenger car product line since the inception of Series/Parallel cooling fan controls in 1994. Relay #1 is responsible for starting BOTH fans so Contact burn-up/erosion is inevitable as the fan motors age.


Low speed cooling fan operation should happen around 195-210 degrees (calibration dependent) so you may want to check this.

A/C head pressure will also turn the fans on, If I were to guess.....
Low speed on at 220 psi
High speed on at 250 psi