1997 gmc 5.7l running cool

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mitch
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Joined: Sun Jul 06, 2014 6:26 pm

1997 gmc 5.7l running cool

Unread post by mitch » Fri Jul 11, 2014 10:38 pm

Hi I have a 1997 gmc 5.7l that is running at 70•c. So I went and bought a new thermostat that opens at 90•c ( 195 F). After I installed it I took it for a drive and it still opened at 70•c. What should I check next?

 

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carriedi
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Re: 1997 gmc 5.7l running cool

Unread post by carriedi » Sat Jul 12, 2014 4:25 am

if your gauge is what you are using for the temperature, try using a scanner and see what the scanner says the temperature is. maybe the gauge is off. the scanner will give you a digital number of the degrees that you vcan compare to the gauge readings.

mitch
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Re: 1997 gmc 5.7l running cool

Unread post by mitch » Mon Jul 14, 2014 5:33 pm

So I've changed the thermostat and the ECT sensor. And when I take it for a drive in the morning it goes up to 100•c then drops to 70•c then stays just over the 70•c mark the entire time I'm driving so I checked the temp with a heat gun right at the thermostat housing and it says 72•c so the gauge is working. What do I try next before changing the thermostat again? Just incase I got a bad one.

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carriedi
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Re: 1997 gmc 5.7l running cool

Unread post by carriedi » Tue Jul 15, 2014 10:27 am

your thermostat should start to open at 188F (87C) and be fully open at 206F (97C) if your truck is running at 70C (158F) it is just barely into normal range for closed loop operation (usually around 160F) Since you stated that it did go to 100C then opened and cooled down to 70C, it sounds like it did wait until the right temp to open.

do you have an electric fan? is it coming on and bringing the temp down? do you have a fan clutch that is staying on? when did this problem start happening? If you have an electric fan, it should not turn on before the engine temp reaches 212F (100C).

mitch
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Re: 1997 gmc 5.7l running cool

Unread post by mitch » Tue Jul 15, 2014 10:44 am

This truck has been running at 70•c since I've owed it the past year and I'm just figuring out it's giving me starting problems when it warms up. Ok yea that makes sense and it going up to 100•c then cooling off only happens the first time you start driving in the morning. Then it stays at just over 70•c on the gauge after that if you keep driving it during the day. It has a clutch fan. Is there anyway to test a clutch fan??

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carriedi
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Re: 1997 gmc 5.7l running cool

Unread post by carriedi » Tue Jul 15, 2014 6:21 pm

let the engine warm up until it is at the normal running temperature for your truck. (after it comes back down from the 100C to the 70C) then shut off the engine and see if you can spin the fan by hand. you should be able to spin it. also do you know if you have the factory radiator or not?

mitch
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Re: 1997 gmc 5.7l running cool

Unread post by mitch » Wed Jul 16, 2014 9:25 am

So I did what you said this morning and it when I stopped the engine it was at 70 and the fan spun pretty easy. I'm pretty sure it's an original rad. How would I tell? What do I check next?

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carriedi
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Re: 1997 gmc 5.7l running cool

Unread post by carriedi » Wed Jul 16, 2014 7:42 pm

You may have to get another thermostat to make sure you have the right temperature one. On your temp gauge in the cluster, there is a normal range in the center part and then there is a cooler range and a hotter range and then there is a red overheat range. Does your engine run below the normal range area?

I noticed that you said that you you're starting to have problems starting. The temperature your engine is running should not give you any warm starting problems. what kind of starting problems are you having?

mitch
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Re: 1997 gmc 5.7l running cool

Unread post by mitch » Wed Jul 16, 2014 8:29 pm

It is running cooler like the gauge needle is at a quarter and I think that's what I'm gonna do is buy another thermostat. There cheap. The starting problem is when I drive for awhile then stop for a couple minutes and start it again. It cranks over hard and weird ( that's at 70•c) so this morning when it got to a 100•c I stopped the truck and started it back up 30 secondes later and it fired right up so that's why I want the temp to be running around a 100 and not 70. I will let you know what a new thermostat does when I get one in.

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