LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Overheating LT1, help!!

Old 06-10-2009, 03:52 PM
  #16  
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First, do not bleed the cooling system with the engine running. If you open the bleed screws with the engine running you can suck air into the system. You use the bleed screws when you are filling the system without the engine running.

Open them, fill the system until you see coolant/water coming out both of them...then close them. Fill the radiator to the top(if it's not already) and put the cap on. Make sure the overflow reservoir is filled to the hot mark. Turn on the heater wide open. Vary the engine rpms for a while(make sure it does not overheat...if it does...you have other problems rather than air in the system). Shut it down and let it completely cool off. After it cools down, check the level in the radiator make sure if it is full. If not, top it off. If you wish, you may open the bleed screws with the engine off to make sure there is no residual air trapped up top.

I suspect the bubbles you are seeing, after 6 or 7 minutes, is the water getting above 212*. When it does...and the water not under pressure(without the cap applied)....it will boil and create bubbles....run it long enough after that and it will boil over big time.

Last edited by ACE1252; 06-10-2009 at 05:06 PM.
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Old 06-10-2009, 04:42 PM
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thanks ace
I'll try this procedure. I suspected I need to add more coolant to water and I was bleeding the system improperly. So I'll give this a try...
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Old 06-10-2009, 06:50 PM
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Coolant is needed to lubricate the pump, keep the water from freezing, and to lower the friction of the water drop to form allowing for smaller drops (that at least what "Water Wetter" does) among other things. Pure water would make it run cooler but could freeze and not lub the pump.

I open the bleed screws with the engine's running. Never had a problem with it sucking air in. Even in Shoebox's tutorial it mentions bleed them and monitoring the temperature (which eludes to the engine running). Make sure the reservoir has coolant in it as well.

Look under "Easy Thermostat Change out" here:

http://shbox.com/1/4th_gen_tech2.html#cooling

Hal

Last edited by Hal Fisher; 06-10-2009 at 06:55 PM.
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Old 06-10-2009, 07:10 PM
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Originally Posted by Hal Fisher View Post
I open the bleed screws with the engine's running. Never had a problem with it sucking air in.
Under certain conditions(not full of coolant), it can suck air in.....but if it's completely full then it usually will not.

I did omit one instruction from my directions.

When first filling the system....after you close the bleed screws....the GM service manual says to run the engine with the cap off until the thermostat opens....then fill the radiator up and put on the cap. In doing this you have to be careful. If you fill the radiator too full, while waiting for the thermostat to open, the system can overflow with the cap off(due to heat expanding liquid). Once the thermo opens, you will know it because the level will drop in the radiator quickly. That is....if the system was completely drained. Being partially drained, it could act differently.

As much trouble as he is having, I'm not so sure that air in the system is his problem.

I've watched techs at Chevy jack up filling my cooling system correctly....and it never overheated. When I checked the radiator(after cooling completely down), it was only 1/2 full after getting home. Even then...it never overheated.

Last edited by ACE1252; 06-10-2009 at 07:18 PM.
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Old 06-10-2009, 07:15 PM
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I'm pretty sure you need the bleed screws open even with the cap off. The water doesn't go down, or at least not very fast, if you leave them closed.

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Old 06-10-2009, 07:23 PM
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Originally Posted by Hal Fisher View Post
I'm pretty sure you need the bleed screws open even with the cap off. The water doesn't go down, or at least not very fast, if you leave them closed.

Hal
When the thermostat opens...it will fall like a rock, but that does not happen until around 180*.

GM says to close them after initially filling it with the engine off. They never mention opening them again. I've done this numerous times with excellent results. I think we over complicate the issue by trying to bleed with the engine running. I, by no means, am saying he has to do it my way, but I've created myself problems by opening them with the engine running.

Last edited by ACE1252; 06-10-2009 at 07:39 PM.
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Old 06-10-2009, 07:31 PM
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I have this.....

http://www.lislecorp.com/tool_detail.cfm?detail=244


This thing works really well for air pockets trapped in any cooling system. Just a word of caution. Do not let the engine temp get above 212*. Without the cap on the system....it will boil and go everywhere.
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Old 06-10-2009, 08:08 PM
  #23  
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good work guys
i will be cautious, and I truly think it really is the water pump.. I'll update tomorrow , if it doesn't cool down then I'll raise it up and chnge the pump on the weekend.
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Old 06-11-2009, 04:55 PM
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Ok guys, here it is, I ran the car with the heater on full blast and all the way to the hottest setting. The air never blew hot, at best it got mildly warm. This I attribute to the temp outside. Hal, I think you win the prize. It is definitely the water pump. She didn't get hot rite away, but I now know there isn't any flow happening. There is still no water on the front passenger floor; so no heater core issue. Replacing the water pump this weekend, hopefully that does it. I completed the throttle bypass as well.

thnks for the feedback, will update soon.... any suggestions on increasing HP, while maintaining natural aspir.
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Old 06-15-2009, 02:37 PM
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Hello,
Ok the latest replaced water pump and did oil change this weekend...Overheating problem solved and car now operating at about 175 to 180....!!!! hooray and thank goodness....! BUT new problem arose, no oil pressure...When I took on test drive it spuuterred and ran real rough. Initiallyoil pressure would rise to about only 20psi!!, I realized a hose from the cover to the thottle body and another hose wasnt fastened. I ran it again and when driving at speed it rose to about 40psi, but when I came to stop at intersection or stop sign it would drop to about 20, and then down to ZEROpsi and my check gauge light came on. I managed to slowly make my way back home as engine seemed low on pick up. It also wanted to cut off in reverse when I backed into the garage... Please help... what could it be that is making it loose pressure when I come to a stop or am not accelerating? All I did was change the oil, could anyone tell me where the sensor or sending sensor is for the oil pump?
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