Ok. Put in new water pump with new gasket, tophat seal and rubber washer on red pipe. Still leaks (drops) from top hat area even though I used a jack and 2x4 to help compress the seal. I've tried this a couple of times and same thing. It doesn't seem like this should be that difficult. Is it possible, or is it known for block to develop any pinhole leaks in the top hat area?

 

Did you use a Volvo OEM seal? If not, that's your problem unless it got pinched or something weird like that is going on. Shouldn't be anything complicated.

Compressing the seal is a non issue. If the bolts went in nice and snug, that's your indication of a right fit.

 

Thanks for the note. Ordered from FCP not sure if OEM or not. But, in looking to buy one from TASCA I see that TASCA parts diagram shows a thermostat sitting in the top port of the water pump (where the top hat seal is located). There was no thermostat when I removed the pump so not sure what this diagram refers to. Should there have been one?
THERMOSTAT for 1994 Volvo 940|273307

 

No, the drawing is confusing. The thermostat is a the end of the top hose, in the housing. The Tasca parts are OEM Volvo.

 

Just pulled my water pump off y/day. After I installed a new pump a weeks ago, after a leak, I didn't put the red pipe washer on the pipe first. When installing, I pinched it within the pump housing and still had a leak.
This time, I put the washer on the pipe and with some permatex gasket seal, slipped it on without issue. Since I wasted a gallon of antifreeze last time, I checked for leaks first and all okay.
Like most projects, there's always "a right way" to avoid issues.

 

You shouldn't have to use sealant on there but if it was necessary, OK.

Definitely avoid using sealant on the "top hat" rubber washer that seals the pump to the head--it causes problems later...

 

Since doing a few water pump replacements on my buddy's '95 940, and my own '93 940, I've found that you MUST lubricate the rubber with silicone grease or di-electric compound, just for lubrication purposes.

The first time working on my buddy's car, I installed them dry. The o-ring folded over itself unbeknownst to me upon installation, and that damn thing leaked every day for almost 5 years consistently. He just dealt with it. Eventually it gave up the ghost and started puking pretty good. As soon as I finished the install, I had that o-sh** thought that I should've lubed the rubber. Lesson learned!

The second pump on his, and the pump on mine haven't leaked a drop yet.

 

Smith, I take you're referring to the small rubber washer down to the heater core?
I agree that the fit must go inside the water pump opening almost 3/4", and for it to "slide" in without curling or cutting, a little lube goes a long way.
I too, learned the hard way.
I also put some permatex on the top washer, although as others have indicated, probably not necessary if you get it up and snug with all bolts.

 

Yeah, the one that goes over the metal pipe. Not a single leak after lubing the o-ring first.

On domestics, I always used a little Permatex Ultra Copper on water pump or thermostat gaskets to keep leaks at bay, but these Volvos are a much better design. I haven't had to use sealer on anything in this car so far.