Water pump is killing me

[eight8toy]

I just went through the same thing last week. Pressure tested and saw the tiniest wet spot, even had a good size leak at the radiator. I said the hell with it and filled it with coolant and under normal engine running pressure I haven't seen any leaks.

New DPI rad with fans is sitting in my garage but I dont have time to work on it now since I'm moving.

[Ron]

I've never put the mixture unit back it, or put coolant in because both times it's not held air pressure at 15psi. I've only tried it with air only no coolant, This morning I pumped it up (with just air) and after a few minutes it was at 14PSI not 15, and then eventually like 10psi after like 5 minutes. Soapy water revealed air bubbles forming around the gasket. I can go add coolant and see if it holds, but then if it dosent I'm gonna have a mess on my hands.

Ah, OK. When you said "seal" I thought you meant the shaft seal...why David an I said to fill it with water...

Since it is leaking at the gasket, something is probably wrong with the mating surfaces: using RTV, warped pump housing, heavy sanding/scraper marks, or chips, as Nick suggested.

[Parzival]

Ah, OK. When you said "seal" I thought you meant the shaft seal...why David an I said to fill it with water...

Since it is leaking at the gasket, something is probably wrong with the mating surfaces: using RTV, warped pump housing, heavy sanding/scraper marks, or chips, as Nick suggested.

ok, taking it back off, (Dana AKA DMC-81) are gonna both revisit it Tuesday as he has graciously invited me to bring it by his place.

[David T]

You really do have to pressure test the cooling system with liquid inside. If you don't want a mess just use water, you can dump it out and refill with anti-freeze after you find and fix any leaks. You can even drive the car a little with just water in it but don't do it for too long. Automotive cooling systems are not made to be tested using just air. Air will leak out of tiny holes that liquid won't.

[Ron]

ok, taking it back off, (Dana AKA DMC-81) are gonna both revisit it Tuesday as he has graciously invited me to bring it by his place.

Cool!...I think he will spot the problem.

[Parzival]

You really do have to pressure test the cooling system with liquid inside. If you don't want a mess just use water, you can dump it out and refill with anti-freeze after you find and fix any leaks. You can even drive the car a little with just water in it but don't do it for too long. Automotive cooling systems are not made to be tested using just air. Air will leak out of tiny holes that liquid won't.

I think you're right, but how huccch leaking is likely to be stopped by liquid? Its losing 1 psi every minute or 2. That doesn't sound like too much?

[Ron]

I think you're right, but how huccch leaking is likely to be stopped by liquid? Its losing 1 psi every minute or 2. That doesn't sound like too much?

I'm thinking we're not all on the same page...what we are saying is:
1. Paper gaskets (used between pump and engine) should never leak, ever!
2. The pump seal (used between the pump housing and pump shaft) may leak air but shouldn't leak coolant. (Especially true if you have let it run a few minutes to seat in, which is not normally required.)
3. If the coolant, engine, and ambient air temps are the same when you fill the system then pressure it at or below the caps rate, it may drop a few psi the first few seconds (hose stretch etc), then hold solid for at least 2 minutes.

Detailed instructions attached below. (Note it even says to wet the cap when you test it.)

[Parzival]

I'm thinking we're not all on the same page...what we are saying is:
1. Paper gaskets (used between pump and engine) should never leak, ever!
2. The pump seal (used between the pump housing and pump shaft) may leak air but shouldn't leak coolant. (Especially true if you have let it run a few minutes to seat in, which is not normally required.)
3. If the coolant, engine, and ambient air temps are the same when you fill the system then pressure it at or below the caps rate, it may drop a few psi the first few seconds (hose stretch etc), then hold solid for at least 2 minutes.

Detailed instructions attached below. (Note it even says to wet the cap when you test it.)

its the gasket. Its just leaking air (thats all thats in there) at 15 psi the hand of the gage is not visibly moving, but after two minutes or so it will be down to 14 PSI. Spraying soapy water around the seem between the water pump front and back (where the paper gasket is) is produces foam, indicating that air is getting out.

[David T]

its the gasket. Its just leaking air (thats all thats in there) at 15 psi the hand of the gage is not visibly moving, but after two minutes or so it will be down to 14 PSI. Spraying soapy water around the seem between the water pump front and back (where the paper gasket is) is produces foam, indicating that air is getting out.

It should not leak once you fill the system with water. Water will cause the gasket to swell and stop leaking. The air is leaking through the paper. Try using water and tell us what happens.

[Parzival]

It should not leak once you fill the system with water. Water will cause the gasket to swell and stop leaking. The air is leaking through the paper. Try using water and tell us what happens.

Ok, I took it out, but have not separated it. I'm taking it over to dana's house tomorrow for further inspection. If we thinks it good, I'll do that and let you know. or if we pull it apart and try again with a new gasket.
His held 15 PSI over night with just air in the system. Like you said, that might not be necessary, but it's damn impressive. you know you did one hell of a detailed job on you cooling system if it does that with no liquid in it. My water pump was not even leaking before. It was just original and I didn't want to worry about it. So I decided to do this preventative approach. This is my second time into the valley, and I don't mind the practice, but I would like to go for a drive before too long, so I want to get all this back in. I'll keep you posted..