I have a radiator that leaks- under about 5lbs of pressure it hisses out in a few tiny spots in the radiator (I put a pressure gauge/pump tester on it) but while driving doesnt take more than a gallon an hour of driving (I have to keep topping it off).

Under no pressure, like while standing still, it stays full for weeks. Is there a way (like leaving the cap off) that I could go 2-4 hours of highway driving where it runs cool with no pressure on the cooling system? (at the other end of this trip is my trusted garage). If I stop every so often and make sure I'm topped off, is there a way to eliminate pressure on the cooling system so I can safely make such a trip? Would leaving the radiator cap off do it?

Sorry if this is a silly question, but hearing from those who know would put my mind at ease... thanks!

 

I would try some AlumAseal Stop Leak Powder to at least get you where you are going.

 

Yes, but does leaving the radiator cap off allow cooling for the engine without buildup of pressure in the radiator?

 

Yes...but without pressure the temps don't stabilize as they should and there will probably be some loss of coolant as it expands and then pukes out the filler neck...and then the radiator will be low on coolant...which is what you are trying to avoid.

Try the Aluma powder...I have yet to have it fail to stop a leak when used as directed.

 

Leaving the rad cap off is a bad idea, it will just puke out all the water. I did this by mistake so I know.

ALUMASEAL Radiator Sealer Powder, .70 oz - G2110647 at Zoro

alumaseal is worth a try.

Driving for 1-2 hours than let it cool down and refill is a workable plan. This is the safest answer.

Idea answer would be a 2 PSI cap. or maybe removing part of the sealing rubber on the cap, but then you would have to buy a new cap.

The older style rad caps had a lever on top that released pressure by pulling up the lever. So if you left the lever up it wouldn't build up pressure.

Good luck and take the safest approach to getting the truck to the garage to get it fixed.

Jim

 

http://ecx.images-amazon.com/images/I/4159N4MW35L.jpg

Here is a picture of the rad cap with the pressure release lever.

This will only work if you can create a small air leak by cracking the release lever a little.