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· Registered
28 Posts
Discussion Starter · #1 ·
1981 GMC Sierra 4x4
350, 3spd, 3/4ton

I just recently bought this truck. I bought it knowing it had the coolant problem but never thought it would drive me crazy. When i start the truck, it heats up quickly, within 2-5 minutes, then the temp gauge goes up just to the redline (not farther) for awhile and hovers there. After about 10-15 minutes of easy driving it will drop down to about 1/4, then back up to around 1/2 (where i want it) and it will stay there regardless of my driving. I can shut it off, then start it up and it will do it again no matter how long/short i leave it off for.

What I Tried:
The thermostat has been replaced twice in the last 7 months
The temp. gauge sending unit is new.

Anything else:
The radiator hoses have been replaced recently (the receipts say so) but i'm not sure it is the proper radiator.
I have a radiator from a 305 camaro that is a bit smaller but when i hooked up the hose to it the water ran through it faster than the one in the truck. Thinking of putting it in, good or bad idea?
I do have to keep topping it up with water, as the radiator leaks a bit.
There is only water no coolant in it.

Could it be a badly clogged radiator? or the wrong one?
Is it the water pump?

I would like to start my truck and it go up to normal operating temperature and stay there, not to go really hot for 15 minutes then cold then normal.

Email me please for any unclarities in my post.

· Registered
7,716 Posts
Fix Radiator first...

Doc here:pimp:

First off fix the Radiator first...If it's leaking it's contributing to your minor overheat (no pressure build up, loss of coolant)

I don't know if the 305 radiator is going to play well in a may want to have yours rodded (<--SP?) and recored...or If you can catch a sale, get a new one..

Clean, flush and back flush the system after you install the new radiator, to get the Crap out of the block.

After you fix that, add and Run a 50/50 or better mix of anti freeze.

Do you have a proper fan shroud? If not run...don't walk to the nearest boneyard and get one and install it ...It will not run cool without one.

If you don't already have one, get and install a coolant recovery kit This will help purge air from the system, without losing coolant.

Between the leaks, the lack of anti freeze, and loss of coolant, no pressure, the thermostat is probably really p*ssed off at you...trying to figure out what you want...and hence the excursions on the gauge.

Water pumps usually Is or isn't ... not once in a I'd put that on the back burner...

Try these items, and I think you'll find the results your looking for!

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