couple trivial questions about replacing a water pump

[deniss]

I've never drained coolant on this car, but I do want to replace my water pump, so I guess I'll need to drain *some* of it. I found the drain plug on the bottom of the radiator not far from the battery and the major grounding point on the front cross-member. When you drain coolant, do you just open the drain plug and let the coolant splash all over the frame?? Or is there a hose you can put on the drain plug to direct it downward and avoid spilling coolant all over the frame?

For water pump replacement, I don't want to drain the whole cooling system, but how much drainage is enough?

Oh, and is it OK to install a Hepu (Germany) water pump instead of "Genuine Saab"? They cost half the money on eEuroparts, so I thought I'd ask about it.

Thanks.

[RickyS]

It would be a good idea to replace all the coolant, and flush the system when changing the pump, unless you have changed the coolant recently.

There is also a second drain plug on the engine block under the exhaust.

[deniss]

Yea, the coolant flush was done several months ago, so I figured I'll get away with just draining enough to replace the pump for now - I don't have the equipment to deal with coolant-flushing the entire system.

[RickyS]

You have to drain quite alot out to get below the level of the pump.

You only need a hosepipe to flush the system!

Some pumps are not good quality - they do not have cast impeller.

[cdaly]

If there's recent coolant in the system, use a hose on the drain plug and catch the coolant for re-use.

[deniss]

Originally Posted by cdaly

If there's recent coolant in the system, use a hose on the drain plug and catch the coolant for re-use.

Do any of you generally apply sealants when you do a water pump replacement job? Tom Townsend on his website recommends using a thread sealer on the two longer bolts, as well as Loctite #518 on both sides of the gasket... Does the Loctite work as the thread sealer as well?

[Albert Trout]

I replaced mine last year and didn't use any sealants and haven't seen any leaks at all. Didn't even consider it to be honest. Don't see that it would do any harm if you're concerened about it right enough. Just get the gasket wet before you put it on so it stays in place when you're putting the pump on.

[philjohnhb]

I have just replaced mine - no sealant required.

[RickyS]

There should be a gasket with the pump. That is all you need. I use some Hylomar as well, but is probably not essential.

Loctite 518 is a flange sealant. It's generally used instead of a gasket, or where a gasket is no longer available.

[Banman]

Replaced my pump a month ago with a junkyard unit so no gasket. I used a very thin coating of Locktite RTV (blue) on the flange. There has been no leaking after several 1000 miles. In general I don't use gaskets, just an appropriate flavor RTV...

[deniss]

I'll definitely use the gasket that comes with the pump, and I did order the genuine Saab water pump - I have confidence that it should work without a sealant. Generally, I don't like using sealants unless necessary. I never used any sealant on the valve cover gasket, for instance, and never had any problems with it leaking.

I'm waiting for the water pump to arrive, and I'm hoping that getting the old seal out won't be too much of an ordeal...

[gorper]

Originally Posted by deniss

Do any of you generally apply sealants when you do a water pump replacement job? Tom Townsend on his website recommends using a thread sealer on the two longer bolts, as well as Loctite #518 on both sides of the gasket.

He recommends this because it keeps the car from coming back to him later down the road with a leaking gasket. The 518 *works*. My favorite local Saab shop does this, too -- they put it on both sides of paper gaskets because it keeps cars from coming back. It's cheap insurance.

Originally Posted by deniss

Does the Loctite work as the thread sealer as well?

Yes.

Originally Posted by deniss

When you drain coolant, do you just open the drain plug and let the coolant splash all over the frame??

You can do it this way; just put a tub beneath the drain.

Originally Posted by deniss

Or is there a hose you can put on the drain plug to direct it downward and avoid spilling coolant all over the frame?

Measure the drain O.D., go to Home Depot, and buy a few feet of vinyl hose from the plumbing dept.

Originally Posted by deniss

For water pump replacement, I don't want to drain the whole cooling system, but how much drainage is enough?

Who knows -- half? 13/16ths? Just drain the radiator.

Originally Posted by deniss

Oh, and is it OK to install a Hepu (Germany) water pump instead of "Genuine Saab"?

Hepu is fine; however, I have installed three of their pumps and they *all* have a high-pitched whine. I am the only one to notice -- my passengers would never know; it's subtle and you may not notice it. I have had one Hepu that had a flange that wasn't fit to the pump properly and the pulley wheel wobbled (replaced free under warranty). Laso is another decent brand.

[deniss]

Great advices - thanks!

I got the hose already... And a nice clean bucket... Anyone know the liter capacity of our radiators, so I know how large a bucket to have handy?

[900t]

Originally Posted by deniss

Great advices - thanks!

I got the hose already... And a nice clean bucket... Anyone know the liter capacity of our radiators, so I know how large a bucket to have handy?

10? That's total, most is in da block. You only need a few L unless you're changing coolant too (good idea)

[Jim Mesthene]

Even if you drain the radiator it's going to dump a bunch of coolant out when you remove the pump, unless you drain the block.
Because of that, many people don't drain anything and let it belch out the coolant through the water pump opening.
Most professionals glue the gasket to the pump for convenience and apply RTV for insurance.

[deniss]

How about this: remove coolant from the expansion tank, disconnect the expansion tank, open the thermostat bleeder valve, and drain coolant from the expansion tank hose. This should take out whatever coolant is on the same level as the water pump, right?

[Jim Mesthene]

It's easier, and more effective, to just drain the block.

[deniss]

OK, I got the old water pump off the car. It appears that whoever did this job before me just used the sealant without the gasket. I had some fun trying to scrape that stuff off the water pump housing using the knife blade. I'm not sure if I gouged the surface in some places while doing this, but I then used the very fine grid sand paper to polish that surface, and it looks as clean as it's gonna get.

I'm thinking though that I should perhaps use the Loctite sealant myself, just to make sure that water will not sip through any surface irregularities?

It appears that some of the bolts also had thread sealant on them - pretty much like Tom Townsend recommended. Should I go ahead and use thread sealer on them as well?

[gorper]

Originally Posted by deniss

Tom Townsend on his website recommends using a thread sealer on the two longer bolts, as well as Loctite #518 on both sides of the gasket...

Put the 518 on. All will be right with the world. At least until the next time your car breaks down. But at least it won't be because of a bad water pump gasket.

[clarkandrew45]

Originally Posted by deniss

OK, I got the old water pump off the car. It appears that whoever did this job before me just used the sealant without the gasket. I had some fun trying to scrape that stuff off the water pump housing using the knife blade. I'm not sure if I gouged the surface in some places while doing this, but I then used the very fine grid sand paper to polish that surface, and it looks as clean as it's gonna get.

I'm thinking though that I should perhaps use the Loctite sealant myself, just to make sure that water will not sip through any surface irregularities?

It appears that some of the bolts also had thread sealant on them - pretty much like Tom Townsend recommended. Should I go ahead and use thread sealer on them as well?

Okay, i tried this replacement of housing using a knife, and its been hard for me. I know this was quite old, but im still looking for some alternatives aside from using the knife.