im trying to figure out where to start with trouble shooting my overheating problem. the gauge started reading over 220 while idling got up to around 243 the other day, put it in neutral and revved it to around 1200rpm and it dropped to around 209, it also goes down when driving. Not today it wasnt responding to my little trick. So i was assuming it was the fan but then it started to rise while driving, but under load it would sometimes drop then change up to where it would drop when i let off the gas or it shifted. Should i start with the clutch the thermostat is getting replaced no matter what and the radiator i think was changed out before i bought it. I have recently driven it on a 30 mile road trip (mostly interstate miles) with no problem im a stickler when it comes to watching gauges. any help would be very much appreciated thanks in advance I love this site. Forgot to mention I have a cold air intake with throttle body spacer and a stainless header with new exhaust to the back
NEED HELP overheating 2002 TB EXT
- Thread starter bobo52
- Start date
gmcman
Member
- Dec 12, 2011
- 4,656
Normal temp for the I6 is around 210, and even close to 220...maybe 216..not sure, is within spec.
I agree when the needle starts to climb out of what's been the normal range it will raise a brow.
Have you verified the coolant level? I try to check with the engine cold and the front slightly elevated to avoid spillout.
I would like to think the clutch fan should be considered. You can disconnect the coolant temp sensor and it should go into a failsafe and fully engage the fan. Try this and see if it engages.
Generally these engines start to run cold with a failing thermostat but can't rely on that.
Another option we obviously don't want to see is a failing head gasket. This can aerate the coolant and cause overheating, a leakdown test can answer some of those questions.
I agree when the needle starts to climb out of what's been the normal range it will raise a brow.
Have you verified the coolant level? I try to check with the engine cold and the front slightly elevated to avoid spillout.
I would like to think the clutch fan should be considered. You can disconnect the coolant temp sensor and it should go into a failsafe and fully engage the fan. Try this and see if it engages.
Generally these engines start to run cold with a failing thermostat but can't rely on that.
Another option we obviously don't want to see is a failing head gasket. This can aerate the coolant and cause overheating, a leakdown test can answer some of those questions.
Mooseman
Moderator
I would also suspect the fan clutch. You can also use this method to check it:
How to test the electro-viscous fan clutch
The thermostat can fail either closed or open. If yours had failed, you would get bigger temp swings. To me, radiator seems to be working OK since it comes back to normal once you get moving.
How to test the electro-viscous fan clutch
The thermostat can fail either closed or open. If yours had failed, you would get bigger temp swings. To me, radiator seems to be working OK since it comes back to normal once you get moving.
coolant level is good, did notice a leak on the passenger side hose by the pipe awhile ago, the heater hose had a pinhole in it, fixed that. Just today there was a puddle after i saw the temp get near the 260 mark, the digital gauge was reading 252. So another question is if there is air in the system would it act the same way
also i noticed how loud the fan was, not that it was loud but was holding longer than before, like and old hotrod with a clutchless fan in it
I checked at the overflow. I just went out to look again and this time I took the radiator cap off and had to add about 3/4 of a gallon so I'm assuming now that there is a leak somewhere but the dipstick did show any sign of water in the oil so I'll test drive it tomorrow and crawl around and look for possible leaks. I also went ahead and bought the fan clutch and water pump since it was fairly cheap as a package deal
Coolant is orange, I may just flush it out since it seems it wasn't taken really good care of before I got it. Let's just say 3 coils were bad and I found a bill for $900 for brake repair
gmcman
Member
- Dec 12, 2011
- 4,656
If it looks orange with no goop, I would save that for a later date.
I would focus more on the fan operation, and if the coolant temp actually coorelates to the gauge.
If you have a bluetooth OBD adapter, you can download the torque app and verify what the PCM is actually seeing from the ECT sensor.
I would focus more on the fan operation, and if the coolant temp actually coorelates to the gauge.
If you have a bluetooth OBD adapter, you can download the torque app and verify what the PCM is actually seeing from the ECT sensor.
Mike534x
Member
- Apr 9, 2012
- 926
The fan is going to sound louder then normal, while trying to keep the engine from overheating on you.
I'm with everyone else on checking the fan clutch, coolant temp sensor, and the thermostat. How many miles on the truck? And when you say you revved it to bring the temp down. Was it quick the needle dropped, or was it steadily climbing down?
I'm with everyone else on checking the fan clutch, coolant temp sensor, and the thermostat. How many miles on the truck? And when you say you revved it to bring the temp down. Was it quick the needle dropped, or was it steadily climbing down?
I'm running a programmer that plugs into the obd, want to put a mechanical gauge in but don't know where the water jackets are. I bought it a year and a half ago with a busted transmission so that was priority to fix, actually overlooked the cooling system until the end because I only ran it every so often. I had it sitting on a lift the whole time, just got it on the road last month
Mooseman
Moderator
I don't think there is any other spot to put another sensor. The stock one is accurate if you don't read it from the dash gauge, which the PCM filters a lot, and use an OBD adapter with something like Torque.
If the cooling system has been neglected, it would probably benefit from a good flush.
If the cooling system has been neglected, it would probably benefit from a good flush.
So you are saying that the computer messes with what the temperature gauge shows just like it does for the oil pressure gauge? I have seen it explained why GM did that with the oil pressure gauge, but why with the temp gauge? Is it because like was just stated, that the 4.2L likes to run at like 216 instead of 195? So then my question is, at what point does the computer show you that it's starting to overheat? Does it show it before damage is done?
Mooseman
Moderator
The PCM will make the driver feel better by showing straight up 210 if it's in the 195-220 range. If it gets hotter than that, I have found that it does show it going up. Heading towards 260 it would show it. Not perfect but better than some others that have a gauge and no numbers. However, with an OBD adapter and Torque, you'll get the real readings.
Update, went through the engine bay and found 2 problems, 1st was the radiator hose behind the alternator had a loose clamp on it, and 2nd the fan shroud was not put back on properly. Replaced the clamp and remounted the shroud. Seems to be running fine, added a 2nd gauge which is tied into the upper radiator hose that gauge reads about 8 degrees cooler than the programmer that is plugged into the obd and has the digital read out which the highest it has read is 210. The weather here has been rainy and Florida cool so I'll have to see if any changes when its warmer. Thanks again for the input y'all, will keep ya posted when the new clutch comes in
