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GM 3400 overheat

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wa9zug

New member
My son has a 98 Transport with 3400. He installed a new thermostat. It overheated shortly thereafter. Must have been fairly severe because it actually burst the plastic side-rail on the radiator. We installed a new radiator. Now it looks like it is still overheating. Heater blows hot. OBD-2 reader says it was 215*. Steam began to pour out of top of engine under the plastic cover. Second thing. When I press the gas and hold it steady, it sounds like I am pumping it. Checked with reader and the spark advance is at about 20* to 30*. No error codes thrown. Any ideas guys?
 


Ok I run this engine you have a crap ton of air in the system. Also are your fans turning on? They cause most of the over heating problem. What happens is the ground gets ruated out or fails for what ever reason make sure when you see it about half way to kick on the ac and max heater that way it wont blow. Also have you done the head gasket yet they are known to fail and cause air to enter the system. And make sure you put thw gtp radiator in it will help keep the temps down as well
 
ericspecullaas said:
Ok I run this engine you have a crap ton of air in the system. Also are your fans turning on? They cause most of the over heating problem. What happens is the ground gets ruated out or fails for what ever reason make sure when you see it about half way to kick on the ac and max heater that way it wont blow. Also have you done the head gasket yet they are known to fail and cause air to enter the system. And make sure you put thw gtp radiator in it will help keep the temps down as well
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Thanks for ideas.

Bleeding air tips?
Any ideas on the pulsing engine thing? Isn't the spark advance reading way out of whack? It almost sounds like the computer is limiting the engine. I press half down on gas and the engine rythmically bounces between 2500 to 1000 rpm.
 
yeah grab a 11 mm and open up the the bleeder on the upper hose then when you see fluid that is air free (mostly) then open the bleader on the passanger side tell fluid comes out then it top it off. make sure you top off the radiator when its all cooled down. i would hate to say this but.... go here http://www.my-chevy-venture.com/forum/ they know more about the van. personally i would do a 3800 swap but thats just me.
 
OK I may have the overheat thing fixed. Thanks for the tips on bleeding. What about my timing at 22*? Did my timing belt/chain jump?
 


It's electronic fuel injection with computer controlled ignition advance and fuel injectors.

Timing advance can be crap load of different numbers depending on what the computer thinks is correct for the time being. Idle advance is normally right around 20ish or so, give or take 3.

If the motor jumped time, your cam and crank sensor would throw codes because there is now an issue.
 
OK, Thanks 55DP, Then I am wondering what is causing the engine to "pull back" when I step on the gas? Ex. Idle smooth, then I step on the gas, it revs up, then pulls back to idle, then revs up, then pulls back. All the while I have my foot on the gas steady. It's as if I am pumping the gas pedal in a rythmic manner.
 
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