radiator troubles

[blizzardwarrior7]

Well, lowered the coolant level, and ran the truck at idle for about 10 minutes, and than drove for about 10 minutes, and than lost the brakes! On the bright side it seems like the radiator issue has been solved! Thanks for the help, now on to dealing with the brake issue..

 

[Gunfreak25]

I suggest you pickup TM 9-8024 off of Ebay if you haven't already. It's a simple brake system once you spent a little time on it. It is a single circuit system, unfortunately. So make sure your steel and rubber hydraulic lines are in tip top shape. Total of 12 wheel cylinders as well that must be in good shape.

 

[Bob USNR]

I assume you put a new or just cleaned/recored radiator in there?? If you put in a used unit you may have installed the problem.
As far as the head gasket goes it may, or may not, blow steam out the exhaust depending on exactly how the gasket failed.
It is possible you might see bubbles from the top tank if the head gasket is blown or the head is cracked.
Got the old fingers for gasket problems only!

I would check the thermostat first. Mostly because it is quick and easy.
If you want to check the thermostat remove it and put it in a sauce pan of water, turn on the heat and wait. The thermostat should be completely open just before the water starts to boil. Typically the temp range from starting to open, to completely open, is under 10 degrees.
I have seen many that open only partially. Causing problems just like you are describing.

On rare occasion I have removed a water pump wherein the impeller had been eaten away or just not firmly on the shaft anymore.
An easy way to check the pump is to remove the thermostat (did I mention this before?) Put it back together and run the engine. Have soldier #2 raise the engine speed to about 1800 while you look into the top tank. You should see a lot of turbulence since there is no thermostat slowing the flow now. And you should not see any bubbles. Bubbles insinuate a head gasket leak.


Remember, if the women don't find ya handsome they should at least find ya' handy!!
e

 

[blizzardwarrior7]

Bob, like I said I think the problem was solved by removing and replacing the thermostat and adjusting the height of the coolant in the radiator. I ran the engine with the belt removed and the thermostat off and no bubbles, water pump is also new.

All the brake lines are in good shape and look to have been replaced in the last 5 years. I am a bit suspicious of the airpack. My pedal has decent pressure going dow n the first time but than takes about a minute to develop any resistance again. On the bright side, I've refilled the transmission with atf and drained out the old oil. Just did an oil change, and got about 70% of the cab sanded and primered. I've used about 5 gallons of degreaser on everything and will begin sandblasting the exles and frame in the next week or so. Ive taken some picture so will post those when i get a chance.

 

[Bob USNR]

I forgot to mention that the amount of space you would leave at the radiator cap depends on the amount of fluid in the system. Easiest way to quantify that is leave it several inches low and adjust when at running temp.

Sorry I did not read the entire thread before. Good to hear all went well and cheaply.
e

 

[Gunfreak25]

Wow, sounds like your doing a thorough clean up and restoration. I know a lot of folks are just fine with the old "rode hard and put away wet" look that so many GMC's have these days. I was fortunate enough to find a GMC that was extremely clean with virtually no mud or caked on crap anywhere on the chassis other than a little driveshaft grease splatter and lots and lots of dirt.

You are right to suspect the AIR PAK. Unless it was rebuilt by the previous owner which is unlikely, it is probably overdue. Even when rebuilt, these things just don't like to sit. Seals and stuff just start degrading. Your in luck, though. As of about 3 months ago the AIR PAK was a huge problem on these GMC's. No rebuilt kits can be found anymore so I think a lot of people put off the idea of buying an M135 or M211. There was a rumor floating around that the 5 ton (m800 series) kits would work, and just a few months ago Jollyroger and Oldfart here confirmed that rumor. 99% of a 5 ton kit will work, except for the two piston seals in the front/top of the air pak. So they found the piston and threaded piece from a 5 ton will work perfectly in the GMC air pak too. Allowing you to use 100% of the 5 ton rebuilt kits. They noticed a slight decrease in braking power, but still more than enough to lock up all 10 tires at will. Just not as touchy, I've only heard stories of how powerful the brakes were in these trucks when fully operational.

 

[bob b]

also have noticed anti freeze coming out of left side of hood while driving good distance, it does not overheat , I had topped off rad. before i drove it 47 miles home from were i was working on it after the repaint and body work, fist thing i checked was to see if over flow tube was blocked and it was not. i am thinking the cap might be leaking , bad gasket possible any suggestions