Water Pump Gasket Leak

[Steve L]

This should be easy. My 1987 325is began leaking coolant from the gasket of the water pump. In 40 years of working on cars, I can't recall ever having a water pump gasket fail before.



I pulled the pump, cleaned the surface of the engine and replaced the pump and gasket, using Permatex Ultra Blue silicone sealer. The pump went in nicely and I torqued the bolts to 16 foot pounds as specified in my manual.


Now that everything is back together, the new gasket is leaking just like the old one. It's possible the the silicone sealer was a little old, but it seemed to come out of the tube and look fine spreading on the gasket. I'm astonished. What do you think I did wrong?



I'm thinking about tossing a can of stop leak into the system. Why would that be a bad idea?

[Kershaw]

Stop Leak will gunk everywhere. Don't do that. Are you 100% sure it's the gasket leaking and not the pump itself through the output shaft?

[e30davie]

Stop leak should only be used in an emergency. And by emergency i mean you are stuck in the desert, 16hrs from civilisation with no water left. if you have water in the previous scenario it is still not an excuse to use stop leak.

[uturn]

1) Are any threads stripped 2) did you spread it evenly on both sides of the paper gasket then 3) install it and leave it alone to cure- 24 hrs without adding coolant?

Are you 100% sure it's the gasket leaking and not the pump itself through the output shaft?

Did you install a new pump?

There's a special place in purgatory for people who use stop leak.

[E30-325iS]

Are you sure the water pump bolts aren't bottoming out?

[Steve L]

Thank you for your responses. I am certain that the gasket is leaking and not the pump for two reasons. I can see the coolant running down the gasket on the right side. Also, when I removed the pump, it was relatively new, but had a plastic impeller. I replaced the pump with a better metal impeller unit. So, the pump is brand new.



The reason why I pulled the old pump was because the gasket had begun to leak. Prior to that, it had held for the few thousand miles that I have put on the car. So, it's unlikely that the bolts bottomed out. When I torqued the bolts, they seemed to press the pump onto the block tightly. I believe the bolts are the original pump bolts. The threads are good. I chased the treads, just to clean them up. Standard procedure along with parts washing everything. The bolts torqued up to 16 foot pounds without trouble.


I have installed many water pumps over the years and this is the only time I have encountered a failure like this. The previous gasket had no gasket sealer, as far as I can tell and the manual didn't mention using the stuff. If I do this over, I will probably use Permatex High Tack instead of Ultra Blue.


OK, so you guys unanimously hate stop leak. Why?

[Steve L]

By the way, I really do agree that using stop leak is a sloppy way to correct the problem.



But I was certain that my first effort would be successful in stopping the leak. Finally, when I pulled the old pump, the old gasket was not damaged. It was in the proper place on the pump. The leak is so strong that it's hard to believe that the coolant started leaking so much through such a thin gasket. The new pump and gasket looks to be on properly.

[jeffnhiscars]

I've always been paranoid about silicon sealants cause I have visions of a excess blob of it getting loose and causing an embolism somewhere. I've used Permatex #2 (non hardening) on water pumps for decades and have never had one leak.

YEMV

[cscracker]

I installed mine with no gasket sealer, just the paper gasket. If your surfaces are clean and flat, it's not necessary.

Are you absolutely, positively, 100% sure it's coming out through the gasket? It's not spraying on there from some other location? No cracks in the metal? Bolts torqued to spec and no gunk in the holes?

[ForcedFirebird]

Are you sure the water pump bolts aren't bottoming out?

I have seen this more than once. If the bolts got mixed up from the timing belt tensioner, they will bottom before the gasket seals.


I have also seen where the pump got hung up on the tensioner. I usually pop the belt and tensioner off when doing a pump just to be sure.