truck overheating

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lenny

Guest
v6 vortex 4.3 GM. Truck come up to temp and than pegs the 260 mark, drops back to 220, back and forth it goes. No leaks, not burning anti freeze, no oil in Rad, no antifreeze in oil or trans. I pressure tested the rad and it holds, 15 lbs running no fluctuation. I don't believe I have a leak into compression and i don't smell coolant burning. So far I have replaced the stat, no improvement, asked a few mechs and said with aluminum intake very good chance the intake manifold has blocked crossover port. I pulled off intake and was fine, installed new gaskets and same old overheating. Now that I look a lot closer I see the heater running lukewarm at best, upper rad hose cold, radiator slightly warm on cap side, cold on drivers side. Seems like probably a circulation problem. I don't know of a way to check the water pump. When I had drained the rad the coolant seemed clean with very little contaminates. Either the rad is plugged or the pump impeller is not turning. Oh yea, with rad pressurized to 15 lbs, it held.

Any suggestions?
 
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lewisb13

New member
This is what I would do. Drain the whole system. Fill it with water, disconnect the tube that comes out of the water pump, start the car, and see if its pumping.
 
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ill marty

New member
Take your radiator cap off run the vehicle till you have heat. This might take time in these temps. If you dont get heat shut the car off let it sit overnight with the rad cap off. Start car and run with cap off till you have heat. Take your time.
 
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sportz700

New member
I just did an intake gasket on my wife's blazer. Got it back together and it ran great but wouldn't throw any heat. Took off the heater hoses and back flushed the heater core. A bunch of crap came out of it. The heater core was plugged. So I ran it for a while again and reflushed it all is good now. It won't cost you but a little time to try. Hope this will help.
 
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lenny

Guest
lewisb13 said:
This is what I would do. Drain the whole system. Fill it with water, disconnect the tube that comes out of the water pump, start the car, and see if its pumping.
Click to expand...

I was thinking about that myself, will try it tomorrow
 
L

lenny

Guest
ill marty said:
Take your radiator cap off run the vehicle till you have heat. This might take time in these temps. If you dont get heat shut the car off let it sit overnight with the rad cap off. Start car and run with cap off till you have heat. Take your time.
Click to expand...

you saying this because you think there is air in the line right?
 
L

lenny

Guest
sportz700 said:
I just did an intake gasket on my wife's blazer. Got it back together and it ran great but wouldn't throw any heat. Took off the heater hoses and back flushed the heater core. A bunch of crap came out of it. The heater core was plugged. So I ran it for a while again and reflushed it all is good now. It won't cost you but a little time to try. Hope this will help.
Click to expand...

If pump is working that will be the next step and the rad flush
 
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stealthv

New member
lenny said:
thanks for the response but I hate throwing parts at it. You can see a collapsed line and I dont have that. Both hoses are good still
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Ah - But you can't see a collapsed lower hose...

From the description, coolant isn't moving.
 
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yamaholic

Member
Water pump, I have same motor did about the samething once like you I changed stat and flushed still did it put new pump on fixed.
 
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lenny

Guest
lewisb13 said:
This is what I would do. Drain the whole system. Fill it with water, disconnect the tube that comes out of the water pump, start the car, and see if its pumping.
Click to expand...

tried that today, what happens is that once disconnected it is not pressurized and will not pump when pump is good. I did it and saw no pumping so I took the pump off and it's appears fine. I asked a guy and he said that test is not accurate. Don't make sense to me because it's a pump driven by a belt and is turning while the engine is running. Fan and clutch seem fine. My only other options are clogged rad or head gasket. With my luck I will deal with every friggin component in the system and the last one will be the culprit, story of my life. Now I have to take the intake off again which ain't all that hard just a lot of electrical connections. Distributor also.
 
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lenny

Guest
yamadooed said:
Park uphill on a decent incline and bleed the air outta it yet???
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no, radiator is considerable higher than motor so air should bleed out if there was any in it with cap off. Newer smaller cars with low rad are subject to not burping but these big old trucks seem to burp easily
 
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