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Hi,
I have a 92 GMC 1500 with a 305 V8 that doesn’t seem to get to the correct operating temperature. I’m thinking correct operating temperature is about 190 degrees Fahrenheit . The temperature gauge doesn’t get above 150, and the heater blows lukewarm. You may be thinking I just haven’t run it long enough, but I don’t think that’s the case, as I have driven for more than an hour hauling 2000lbs of concrete bags in the summer and it still doesn’t warm up. The gauge seems to be working correctly in that the needle seems to move freely. Also, the water pump and thermostat have been replaced. The coolant is topped off.
Any comments or suggestions that I might be able to try are appreciated.
Thanks!
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you could have a stuck open t-stat. Fan clutch running all the time?
more in this link.http://www.ericthecarguy.com/faq/solving-automotive-hvac-problems
Thanks for your response, I’ll look at that link.
I suppose the thermostat could be bad, but even after it was replaced it didn’t warm up, which makes me think it’s something other than the thermostat. I don’t know if the fan is running all the time, but when I have looked it has been running. It seems kind of odd to me though that the fan running all the time would keep the temperature just below 150 degrees all the time.The fan will be turning all the time, look here http://www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Imperial/2007-imperial-fan-clutches.pdf
Eric may have a video on it also.i am having a very similar problem with a 96 blazer 280k+ miles. i replaced the the water pump and it ran like a champ for a few months. i started noticing in nov that the air wasn’t heating up in the cabin. i decided to clean the heater core, and replaced the thermostat (no fail safe). at that point i noticed the temp wouldn’t get above 150 on the dash. the heat was more chilly than anything. i thought the new thermostat was faulty so i replaced it again. both are rated at 195 degrees. no luck. so i figured the coolant was too rich so i drained some and replaced it with water, now i am running a coolant mixture at -10 degrees F, which is still acceptable in my area. at that point i started noticing the temp would raise above 150. it would get to around 195 and then drop to 150. i am convinced that the thermostat is working, i can tell when it opens because it’s like a rush of cold water floods in. the air warm as the temp rises but becomes chilly when it drops to 150. oddly enough i have the cap off of the radiator and i can see steam come out of it, so i know it’s not cooling that much. the only other thing i could come up with is air in the system. so after wasting more time than i like to admit trying to find a bleeder bolt that doesn’t exist… i take it take it to the hill to try to burp the baby. i am still facing the same symptoms. it heats up until the thermostat opens. the only other thing i can come up with is the etc. it’s not that expensive, however i really do not want to open the system again without any evidence that the computer could be causing this some how. i did notice the fan is always running but has done that for as long as i can remember… perhaps this could be the issue but i don’t understand the significance. thought would be normal. can you explain more about how the fan maybe causing my issue? thoughts or suggestion that i have missed would also be appreciated. tks in advance.
Does your vehicle have a heater blend door? Look up the part for your year, make and model online. If it does, that thing could be be keeping the door on cool. Also, for older systems there could be a vacuum leak from the control or the firewall, again causing the blend.door to stay shut for only cool air.
First thing in this situation, especially since the cooling system has been recently serviced, is to check for air in the cooling system.
Ignore the bleeder valve in the video. They just make it easier to fill the system. Do everything else the same though. Once you’ve eliminated that possibility, and you still have an issue, then it’s time to move to other parts of the system for a potential cause. More info here.
http://www.ericthecarguy.com/faq/solving-automotive-hvac-problems
Good luck and keep us updated.
Well I attempted to bleed the cooling system yesterday but I think I did it wrong. I’m going to try again and see if I can get the desired result.
Today was attempt number 2 at bleeding the cooling system. Unfortunately I didn’t get the desired results. I followed the directions in the video, except I didn’t rev the engine up to about 2000 rpm. I learned from my first attempt at bleeding the cooling system that the coolant likes to erupt from the radiator when the rpms return to idle.
The problem I seem to be facing is that the engine doesn’t seem to warm up enough for the thermostat to open and circulate the coolant so that I can bleed the air out of the system. In my first attempt of bleeding the system I did things wrong and lost quite a bit of coolant. But after that happened the temperature gauge did climb, and was reading about 210 degrees. I think what happened in that instance was the coolant was no longer circulating and therefore warmed up. Before attempting to bleed the cooling system today I did fill it up, but today it only would stay around the 135-150 degree range.
Any insight you have regarding this is greatly appreciated.
I had a similar situation before, I did replace the thermostat and that was the problem
If u go to a local auto parts sore u might get a lower temp thermostat, u have to get it from the dealer for your car (I did and fixed the problem)
Take out the thermostat, put it in a pot of water and start heating it on the stove and check the temp with a cooking thermometer.Hope u find the problem
Well, I just removed the thermostat and set it in a pot of water and heated it up on the stove, using a cooking thermometer to measure the temperature. Looks to me like the 195 degree thermostat works perfectly. I’m really at a loss for what could be the problem now. I’m going to top off the motor with coolant, reinstall the thermostat, use the spill free funnel and fill the cooling system and attempt to bleed the air out and see if anything changes, though I’m afraid it won’t.
Well I did just what I described in my last post and I didn’t get any improvement. I don’t know what the source of the problem is so I guess I stop here until I find someone who has had this problem and solved it.
Thanks for all your feedback, but this still remains a mystery to me.
I thought that might be the case, but if that were true I would expect to get hotter air out of the heater…
Does the fan run at the same speed when its cold and when its hot?
The fan should run slower when cold then increase in speed when hot.
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