Water pump won't seal, need advise.

[quikveedb2]

Ok boys & girls I'm getting a bit frustrated with my timing belt/water pump service & I'm gonna ask the r3v gurus to lend a hand. I'm well aware of the tech sub-forums but I need timely help & general discussion gets much more traffic. Yesterday I did the service and everything went fine both on the removal & install up until refilling the cooling system. I followed the instructions that came with the water pump & only used the gasket, no sealant, and as soon as I filled the reservoir coolant came pissing out of the water pump. It's not really a huge surprise, I suppose, and I should have known better. I'm using good parts here as far as I know (the pump is a Graf unit) and on the last tb/wp service I didn't have a gasket since I just checked the previously installed unit for wear, so I used some RTV, and it worked flawlessly for 5 years.

Today I tore it back apart, and found the gasket looking a bit mangled. So, I used some Permatex gasket maker, reassembled, and refilled. No immediate pissing of coolant this time, so I fired it up to start looking for leaks. Everything was fine up until the motor got up to temp & ran for a few minutes, and lo and behold the fucking water pump starts seeping again.

Now I'm gonna pull it back apart tomorrow and assess the situation. I'm thinking that I displaced too much of the gasket maker moving the pump around on it's mating surface trying to get the first bolt to thread, hence the leak. Alternately I didn't let it cure for long enough & the pressure from the system created the leak.

Tomorrow will be my 3rd day doing this service in a row, I've got it down to a few hours at thins point, but I really want to get it right & carry on with my life. Any of you many mechanically inclined r3v denizens have thoughts on what I can do to resolve this issue? I can't believe I got it right the first time I did this years ago & can get it right now...

Side note; should I be concerned about having run the car with the new timing belt installed, removing it to get the pump off again, and re-installing? I know used belts are a no-no on the M20.

TL/DR? You probably can't help.

Thanks r3v!

[accident]

If you're using gasket maker, I'd let it cure overnight before running the car.

That said, you shouldn't need to be using gasket maker. Are you 100% sure the mating surface of the block is clean? I've done timing belts where I found hidden chunks of gasket under what I thought was just grease. Scrape that shit with a razor blade, or even scuff it up with some fine grit sandpaper.

As for the belt, I wouldn't worry about taking it on and off, since you haven't really put any miles on it.

[quikveedb2]

If you're using gasket maker, I'd let it cure overnight before running the car.

That said, you shouldn't need to be using gasket maker. Are you 100% sure the mating surface of the block is clean? I've done timing belts where I found hidden chunks of gasket under what I thought was just grease. Scrape that shit with a razor blade, or even scuff it up with some fine grit sandpaper.

I cleaned the mating surfaces thoroughly before install the first time with a razor. It looked like clean, fresh metal and even had a nice hatch pattern.

Edit; same thing on the 2nd install. Cleaned mating surfaces very thoroughly. I could wipe the area with a white rag I and get no residue of any kind.

[accident]

Has the motor overheated at all? Maybe the block is warped. Are you torquing the bolts?

[quikveedb2]

All bolts have been torqued to spec. The motor got warmer then I'd like once when the heater core blew, but never into the red on the temp gauge.

[accident]

Maybe you got a shit water pump. Something is causing the surfaces to not make proper contact with the gasket.

[Exodus_2pt0]

Stop using gasket maker when a paper gasket is called for. It may have worked once, but it is not a proper repair.

Clean the surfaces, throw a paper gasket on DRY, and it will not leak.

When something calls for RTV only it will have a groove cut into it so the silicone can make an o-ring type seal. I've also found that adding RTV to a paper gasket can also cause problems with squeezing out the gasket upon torquing. Thus, the dry gasket on bare metal surfaces.

Hell many differential covers use RTV only, and they always leak within a year or so. (referring to American style diffs with stamped steel covers) Considering diff's use a much heavier fluid and aren't under a constant 15 psi of pressure, I don't see how your water pump held that long before.

Just saying, if you're having trouble with RTV.... maybe the best course of action is to do the job again, using the parts designed for it.

[SmokeE30]

I have had success with permetex water pump and thermostat sealant in the past just put a very thin layer on to stick the paper gasket to, let it tack up and then put the gasket on and then another very thin layer. You don't want much but I have had good luck with it on m20 water pumps so that itself probably isn't your issue.

One thing that I have seen that could be your problem is if one bolt or more that hold the water pump to the block has been replaced with a bolt that's just slightly too long the bolt will bottom out and become tight before the pump is properly sealed against the block, It took me a while to diagnos one bolt having a couple extra threads on one car that was leaking after 2 gaskets.

[Cletonius]

Maybe you got a shit water pump. Something is causing the surfaces to not make proper contact with the gasket.

I could see this happening.

OP: have you checked the mating surfaces with a straightedge?

[downforce22]

Bummer Dude. This happened to me in February.

I did the water pump and everything only to find when I filled it I had a stream leaking out the pump. The gasket did not get put on right and was ripped a bit in a spot. I grabbed some rtv sealant and sparingly applied it around the edge of the gasket and applied it to the water pump. After it dried I cleaned the mounting surface and just bolted it in. I did not put rtv on the block itself. I put it back together and I have not had any problems for 6 months.

I have heard of people using old belts and not having a problem with them. Having said that I did the pump with the belt still on the car, I just took the radiator and hoses out.

You'll get it together and won't have to worry about the pump for another 50k miles.

[quikveedb2]

First off, thanks for the thoughtful & insightful replies.

@Exodus_2pt0

Re-read my original post & you see that I did install the gasket dry and on a clean surface on the first attempt & it worked out worse than the 2nd when I used gasket maker.

There is a small chamfer around the outside diameter of the water pump mating surface, but I doubt if it's doing much good as it doesn't even appear continuous to the naked eye.

@SmokeE30

I've read in some write-ups to use some Permatex with the gasket, I'm wondering if having more stuff between the block & the water pump will create more avenues for leakage. I did notice that one bolt was missing it's washer when I removed them, and another cracked it's washer during the first install, which I found out wen I removed it the 2nd time. I find it hard to believe that that small amount of extra thread would cause the leak, but new washers will be going in this time anyway.

@Cletonius

Have not, will check when disassembled. I hope the water pump isn't the cause.

@downforce22

The gasket was slightly ovalized at one of the bolt hole locations, not torn at all, and I find it hard to believe that the coolant would leak at the rate that is did from something so small. I dunno how you did the pump without removing the belt as it's part of the tensioner assembly too? Do the 2 tensioner mounting bolts hold the belt in place firmly enough that no tension is lost without it?

At this point I'm thinking I'll redo the job with gasket maker & let it cure overnight since I had better results with it on the last attempt than the gasket. I'm on the fence as to whether new gasket is worth trying since it worked out so poorly before.

You'll get it together and won't have to worry about the pump for another 50k miles.

Thanks for that. :)

[AndrewBird]

I've never had luck with silicone based gasket sealants. I use this stuff:



Put a very thin coat on each side of the gasket, letting each "tack" before assembly. Most of the time, this stuff sticks so well the gasket tears in half on removal down the road.

[Cletonius]

I dunno how you did the pump without removing the belt as it's part of the tensioner assembly too? Do the 2 tensioner mounting bolts hold the belt in place firmly enough that no tension is lost without it?

IIRC, when I did mine, the pump was totally separate from the belt/tensioner assembly. The tensioner lives under the cover with the belt and the pump is in the open. Maybe this is a B25/B27 difference? I remember feeling like my scenario was different than described in the diy articles.

[TobyB]

Have you checked the pump to make sure the sealing surface is flat?

I can't see the block warping enough to do this, but if something went wrong
in the pump casting, IT could be warped.

Quick and easy to check- once it's off- just put it on a very flat surface, and see
how it's sitting.

RTV CAN work for this- it's not the OEM way, but it's gotten 25 years better since the
OEM way was specified. I routinely use it for diff covers, trans housings, etc and it
does well enough...
...but unless I was in a pinch, I'd use a paper gasket, because as noted above, there's
no inbuilt provision for the RTV to make a long- lasting flexible seal.

hth

t

[quikveedb2]

I've never had luck with silicone based gasket sealants. I use this stuff:



Put a very thin coat on each side of the gasket, letting each "tack" before assembly. Most of the time, this stuff sticks so well the gasket tears in half on removal down the road.

That's exactly what I used on the 2nd attempt, and followed the directions. No gasket though, do you think both would net a better result?

@ Cletonious

Interesting, I'm not sure if the B27 water pump is different but I don't think so