Hose leak a sign of a bad radiator cap?

[DeadheadNM]

After much time today the leak about my lower radiator hose at the pump appears cured after exchanging the #15 RC15 cap for a #15 example I had on the shelf from a Vega coolant recovery system.

Originally I thought the leak was do to loosening of an OEM tower clamp. Tightening before and after repositioning didn’t fix the leak neither did adding a buddied up worm drive clamp. I was ready to replace the hose and clean the pump neck when I thought to try a different radiator cap.

Could a bum radiator cap produce the leak? Nothing ever leaked from the overflow hose. Inline tube reproduces an RC15. I plan to order one as a more permanent replacement.

[Steeveedee]

Get a light and a mirror and check the weep hole on the bottom of the water pump. If changing clamps didn't help, it's probably water pump bearing seal. I couldn't tell you why the cap made a difference, unless it doesn't actually hold much pressure.

[truckster]

The only way I could imagine a cap causing a leak other than at the cap itself is if the spring is holding too much pressure. I've never seen a cap do that - when they fail, they don't hold enough pressure. Besides, you'd have to have something else wrong that would cause that type of high pressure.

Here's another possibility - the Vega cap is holding less pressure, so the cap that is working exposed the leak, but running the system with lower pressure keeps it from leaking.

[davischevy]

I'd say the old cap could have been holding more pressure, therefore causing the leak.

I agree with Steve about the water pump possibly leaking out the little hole in the bottom. I have seen them leak intermittently before they completely fail.

There is still a good chance you will end up cleaning the outlet on the water pump.

I too, still use tower clamps.

[DeadheadNM]

Thanks guys. Sounds odd I know. Each cap involved is 15lbs. I’ll double check but when I was watching the leak I didn’t get a sense that the fluid trail led to the weep hole. If present, it would certainly be par for my luck this week with engines. Temperature is running normal.

I’ll make a longer run this evening and see what shakes out.

[Steeveedee]

If it is the water pump seal, drive it around and warm it up, then park it where the leak doesn't make a mess. Once the engine is off, it'll start leaking once the pressure changes. Crazy that it may only leak when shut off, but I've seen it many times.

[truckster]

Go to your local auto parts store and rent a pressure test kit. You'll be able to test your system and your radiator cap and see where the problem is.

[DeadheadNM]

Thanks again guys. It’s leaking still. When all this began there was a small puddle. That certainly improved with attention to the lower hose clamp. However, the drips persist and occur when the engine is running making a mess of the front differential cover. What I’m seeing now could be from the weep hole. I’ll work to confirm that.

I’m going to stock up for a water pump exchange when time allows. Can’t hurt to have spare parts on hand if by chance it isn’t the pump. The radiator that’s in place is a Harrison four row but doesn’t have the take off for the water heater. I’ll exchange it for a rebuilt one I have on hand that does have a take off. The build goes on forever, the party never ends.

[Ol Blue K20]

I bet it's the pump, but I'm watching to see what you find out.

[DeadheadNM]

Engine is cold - I’ll check at operating temp but weep hole looks clean and dry at rest. No coolant residue.

I’m tempted to add an iPhone endoscope attachment to my tool box for tight inspections like this. https://www.amazon.com/DEPSTECH-Wate...=fsclp_pl_dp_1