When I'm driving in slow stop n go traffic around town my car gets hot and sometimes just slightly moves into the red area but never gets quite hot enough to make the dummy light go off. Once I get going about 55 it drops down and sits at the halfway mark like its suppose to. The coolant level is good and both fans are kicking on and running. I'm going to replace the thermostat today and see if that helps. Anyone have this happen before or know exactly what is wrong with it?
'05 Grand Prix is getting hot w/3.8L
- Thread starter volk06
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How many miles? If high mileage, the water pump vanes could be worn down. Also replace the pressure cap.
This car might have two-speed fans. I'd get a scangauge to see if it really is getting up to the "high speed" trigger, usually 230'F or so. With the fans on high you should be able to stand outside the driver's door and feel hot air blowing from under and around the engine compartment. Similarly if you put your hands behind the fans under the hood it should feel like a hair dryer.
Is it any different with the AC on?
If your heat is not blistering under this scenario, it points to a weak water pump. I don't think the thermostat will help much.
Is it any different with the AC on?
If your heat is not blistering under this scenario, it points to a weak water pump. I don't think the thermostat will help much.
Having dealt with a few GM 3800s, they do tend to run on the hot side in stop and go/idling. The low speed fan setting kicks on at like 230 degrees and high kicks on at something ridiculous like 240. They should turn on when the A/C is on. If it's getting into the red while idling, something is amiss. Check and see if there's a bag or something impeding airflow through the radiator. You can try the thermostat; it's easy to change on these engines. There's also a bleeder screw in the thermostat housing to purge air. Also change the cap as mentioned. If it was the water pump, I'd think you'd see the problem show up under load at speed as well. Does it drop back to around 200 when you're on the highway? It should.
If it cools down well at speed it is unlikely to be a water pump.
First probability, fans. In my car one fan can die and you hardly notice until it gets really hot in traffic.
I'm betting on the high speed relay being bad.
First probability, fans. In my car one fan can die and you hardly notice until it gets really hot in traffic.
I'm betting on the high speed relay being bad.
Originally Posted By: The_Eric
Changing the thermostat would be a good place to start - use an OEM one if it's not too late. Have fun bleeding the air out of the system... If you haven't changed your coolant, now would be a great time!
Yep! Start Here ^^^^^^^^
Changing the thermostat would be a good place to start - use an OEM one if it's not too late. Have fun bleeding the air out of the system... If you haven't changed your coolant, now would be a great time!
Yep! Start Here ^^^^^^^^
As said those engines run hot. Low speed fan comes on @ 226 and high speed @ 240. I'm betting on a gauge thats reading high.
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In 95f weather i cant get either of my 3800's over 200f even in stop and go traffic.
One a SC GTP and the other a normally aspirated Grand Prix.
I did a 3800 that was doing similar to yours and while the coolant level looked okay when i drained it i found Dex sludge in the radiator, a local shop cleaned the core out for $50
+1 on the thermostat first, use only GM OEM with a jiggle valve and fill slowly with the thermostat housing bleeder cracked.
One a SC GTP and the other a normally aspirated Grand Prix.
I did a 3800 that was doing similar to yours and while the coolant level looked okay when i drained it i found Dex sludge in the radiator, a local shop cleaned the core out for $50
+1 on the thermostat first, use only GM OEM with a jiggle valve and fill slowly with the thermostat housing bleeder cracked.
Originally Posted By: Trav
In 95f weather i cant get either of my 3800's over 200f even in stop and go traffic.
Really? We've had 3 GMs with the 3800 and they all will run about 220 in stop and go. Actually, the temp will rise to about 225, the fans turn on, and the temp drops to about 205. They run at about 200 on the highway.
In 95f weather i cant get either of my 3800's over 200f even in stop and go traffic.
Really? We've had 3 GMs with the 3800 and they all will run about 220 in stop and go. Actually, the temp will rise to about 225, the fans turn on, and the temp drops to about 205. They run at about 200 on the highway.
Volk, what happens when you run the A/C? Turning the A/C on in high ambient temps should force the fans on at high speed. Check that out, should maybe determine if the high speed fan relay is bad.
I went out and started the car up, I ran some errands earlier this morning. The temp gauge was at 1/4 when I started it. No fans were on when I started it. I turned the AC and the fans turned on instantly.
Is this a symptoms of a bad LIM?
Is this a symptoms of a bad LIM?
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Yes its true, i have had both of these for a few years.
The GTP ran a little hotter but the temp dropped to near thermostat temp when i switched to JD Coolguard original formula and mixed it 50/50. Other than with the A/C on the fans don't come on at all that i have noticed.
They run very cool.
These are not the only engines i have seen this happen to with Coolguard, the stuff must have some sort of wetting agent that eliminates hot spots that may be present in some engines, just my own thought i have no idea really.
No such difference noted in the Ford 5.4 or GM 6.0 that i put it in but Toyota 3.0 and 1.5 showed a noticeable decrease of about 5f in city traffic.
Originally Posted By: volk06
Is this a symptoms of a bad LIM?
Not really, coolant loss (even slight over time) sometimes together with milky oil is a real sign.
The GTP ran a little hotter but the temp dropped to near thermostat temp when i switched to JD Coolguard original formula and mixed it 50/50. Other than with the A/C on the fans don't come on at all that i have noticed.
They run very cool.
These are not the only engines i have seen this happen to with Coolguard, the stuff must have some sort of wetting agent that eliminates hot spots that may be present in some engines, just my own thought i have no idea really.
No such difference noted in the Ford 5.4 or GM 6.0 that i put it in but Toyota 3.0 and 1.5 showed a noticeable decrease of about 5f in city traffic.
Originally Posted By: volk06
Is this a symptoms of a bad LIM?
Not really, coolant loss (even slight over time) sometimes together with milky oil is a real sign.
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Replace the radiator cap! I've had three of three TVS (GM's supplier) caps fail.
Does the GP have a slant-neck radiator? If so, replace with a spring-center cap (Stant 10230), instead of the drop-center design (10231).
Does the GP have a slant-neck radiator? If so, replace with a spring-center cap (Stant 10230), instead of the drop-center design (10231).
JD Coolguard, eh? I may give that a shot!
Originally Posted By: volk06
I went out and started the car up, I ran some errands earlier this morning. The temp gauge was at 1/4 when I started it. No fans were on when I started it. I turned the AC and the fans turned on instantly.
Is this a symptoms of a bad LIM?
The gauge was at 1/4 when you started it cold first thing in the morning? I'd say you have a sending unit or instrument cluster issue.
I went out and started the car up, I ran some errands earlier this morning. The temp gauge was at 1/4 when I started it. No fans were on when I started it. I turned the AC and the fans turned on instantly.
Is this a symptoms of a bad LIM?
The gauge was at 1/4 when you started it cold first thing in the morning? I'd say you have a sending unit or instrument cluster issue.
Originally Posted By: dishdude
Originally Posted By: volk06
I went out and started the car up, I ran some errands earlier this morning. The temp gauge was at 1/4 when I started it. No fans were on when I started it. I turned the AC and the fans turned on instantly.
Is this a symptoms of a bad LIM?
The gauge was at 1/4 when you started it cold first thing in the morning? I'd say you have a sending unit or instrument cluster issue.
No it was at 1/4 because i had run errands earlier in the morning.
Originally Posted By: volk06
I went out and started the car up, I ran some errands earlier this morning. The temp gauge was at 1/4 when I started it. No fans were on when I started it. I turned the AC and the fans turned on instantly.
Is this a symptoms of a bad LIM?
The gauge was at 1/4 when you started it cold first thing in the morning? I'd say you have a sending unit or instrument cluster issue.
No it was at 1/4 because i had run errands earlier in the morning.
Ditto on the radiator cap and replace them every 3-4 years. Also would do a coolant flush and refill with fresh coolant. Dexcool is perfectly fine...
I own an 03 Monte Carlo SS and a 04 Impala SS and both run cool... Radiator drain and fills every other year has kept the overfill bottle and coolant still looking like new.
I own an 03 Monte Carlo SS and a 04 Impala SS and both run cool... Radiator drain and fills every other year has kept the overfill bottle and coolant still looking like new.
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