GM - Engine Cooling Questions
Fleet Owner
Joined: Sep 2005
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From: Lake Tahoe, Nevada
Originally Posted by 85lebaront2
Bdox, if you find a power valve in a Qjet, I would like to see it. Good luck with it.
Lead Driver
Joined: Jul 2005
Posts: 5,967
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From: Eccles, WV
Mike, one thing to check is the hoses. If you have a hose to collapse while running, the vehicle will overheat. My old F150 drove me crazy with a heat problem until I discovered that the bottom hose was collapsing.
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You guys are amazing. 85lebaron2, thanks for the input. I can’t answer your question without looking and doing some discovery so I’ll respond with answers tomorrow. Thanks a lot. I’m printing this thread so I can check off things in the daylight tomorrow. I wonder if my heating issue stems from a frozen advance mechanism. You would think that the truck would have suffered some drivability issue were the timing failing to advance, wouldn’t you?
pmasley: the lower radiator hose has come up – thanks for the suggestion. I’ll swap it out with a new one when I put her back together.
Sure is good to have a panel of experts when I am working on an engine I am not famaliar with.
Thanks again.
-Mike
pmasley: the lower radiator hose has come up – thanks for the suggestion. I’ll swap it out with a new one when I put her back together.
Sure is good to have a panel of experts when I am working on an engine I am not famaliar with.
Thanks again.
-Mike
Lead Driver
Joined: Jul 2005
Posts: 5,967
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From: Eccles, WV
Mike: If that engine has over 80K on it and while you have the front off, maybe want to check the timing chain. It is an easy test using the distributor. If it is sloppy, it will retard the timing and cause an overheat too while traveling on the highway.
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Senior User
Joined: Dec 2003
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Replacement radiator arrived today. I was told that it has brass tanks. The radiator I picked up has plastic tanks. Shop said "uhhh,,,... brass available, wait 2 days, same price."
What do you think? Which do you guys prefer, brass or plastic tanks? I am leaning toward brass, but have no proof that they are better. It just seems like a 24 year old truck should have brass... thats all....
-Mike
What do you think? Which do you guys prefer, brass or plastic tanks? I am leaning toward brass, but have no proof that they are better. It just seems like a 24 year old truck should have brass... thats all....
-Mike
FTE Legend
Joined: Jul 2005
Posts: 65,938
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From: Millersville, MD
Have you checked the possibility that it is the automatic transmission running the temp up? Have you checked the fluid level? An automatic tranny temp gauge isn't THAT much....it could be heating up the radiator enough to increase the engine temp....
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Originally Posted by Bdox
The idea that if some is good, more is better is rampant. Sometimes it's true too. Like with money, when is more not better? But there are things where that ethic needs to be examined.
...
The more costly, and more efficient is the type where the 'fins' are sheets that go all the way across the radiator and are penetrated by the tubes. This provides the most 'fin to tube' contact. Also, this type of fin design is often punched with a great many micro louvers that increase the heat dissapating qualities.
In any case, the more rows the more restrictive to air flow. Bigger area is more efficient than more rows. Point being, there is a point of diminishing returns when adding more rows to the radiator.
...
The more costly, and more efficient is the type where the 'fins' are sheets that go all the way across the radiator and are penetrated by the tubes. This provides the most 'fin to tube' contact. Also, this type of fin design is often punched with a great many micro louvers that increase the heat dissapating qualities.
In any case, the more rows the more restrictive to air flow. Bigger area is more efficient than more rows. Point being, there is a point of diminishing returns when adding more rows to the radiator.
Took your wise counsel. Found a special high efficiency 3 core w/ Brass tanks. Rated higher than the 4 core for heat exchange cap. Sounds like a good part. Should be in Monday.
Thanks
-Mike
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Originally Posted by 85lebaront2
Quadrajets will run with nop or little accelerator pump. In front of the primary barrels, through the vent tube you can see a small hanger with a "tee" shape. Take a small screw diver and see if it moves up and down freely. That is the enrichment system on a quadrajet, it moves the primary metering rods up and down. If it won't move, you'll have to rebuild the carb. Does your truck have a four lead cable coming out from it and disappearing through the firewall? If so you have the ESC system which was prone to failure. You might want to take a good look at the advance system both mechanical and vacuum. HEI distributors are know to develop frozen advance mechanisms. Chevrolet used to use steel shim headgaskets that would leak if ever run hot, then the problem would "feed" on itself getting progressively worse. Bdox, if you find a power valve in a Qjet, I would like to see it. Good luck with it.
2) enrichment system feels free. Moves up and down.
3) 4 lead out of front of dist. then into top of cap (coil) then to other plugs in harness.
4) mechanical advance free.
5) vac. feels frozen- will not move. (!!??)
6) Head gasket issue? No signs but will run sniff test when up and running.
7) Vac hoses all appear to be in better shape than I thought.
Thinking about pulling the vacume diaphram/valve/thing with the hose in one end and actuator arm sticking into dist. from the other end- and seeing if it is frozen. Does this sound like it could be the stumble-on-upshift culprit?
-Mike
Postmaster
Joined: Feb 2004
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From: IL
I would think that would be the problem seeing as everything else checks out. Your vacuum pressure (neg) would naturally be lowest at idle anyway, so any little problem in the system would likely show then. I'm by no means a expert at this, but it seems to me that is your problem. I think the part you're describing is part of the vacuum advance for your timing, can't remember the name, but then again it's not even 5:30AM and I've barely got half my mug of java down. Good luck!
Old School Hot Rodder
Joined: Feb 2006
Posts: 6,472
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From: Exmore, VA
Mike, I think you have found your culpert. The "frozen" vacuum advance is probably actually leaking. Delco vacuum advances will exhibit a "frozen" condition as the diaphram will seal the can at full retard. If you attempt to pull a vacuum on it, you will probably find it won't hold vacuum. The lake of advance at cruise, will make the truck run hot and will most likely cause the stumble on upshift.
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Originally Posted by 85lebaront2
Mike, I think you have found your culpert. The "frozen" vacuum advance is probably actually leaking. Delco vacuum advances will exhibit a "frozen" condition as the diaphram will seal the can at full retard. If you attempt to pull a vacuum on it, you will probably find it won't hold vacuum. The lake of advance at cruise, will make the truck run hot and will most likely cause the stumble on upshift.
fordsflylow & 85bebaront2:
Nice! Thanks for all of your help. I will pull the vac adv. diaphram today and swap in a new one.
Thank you again for all of your advice.
-Mike
Last edited by mschultz; Mar 11, 2006 at 11:36 AM.
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Bolted up new 19" radiator, salvage yard bracket, shroud, 5 blade fan & clutch, new radiator hoses, vacume advance diaphram and vacume lines this afternoon.
Truck runs approximately 15 degrees cooler in town. Idles better and no stumble on upshift. Looking forward to seeing what it does when loaded down. Will be loaded up with equipment on Saturday.
Feels like a solid service truck again.
Thanks for all of your help.
-Mike
Truck runs approximately 15 degrees cooler in town. Idles better and no stumble on upshift. Looking forward to seeing what it does when loaded down. Will be loaded up with equipment on Saturday.
Feels like a solid service truck again.
Thanks for all of your help.
-Mike