cohocarl

Wondering if anyone has any suggestions regarding my water pump leaking at the flange.

Built a 383 and a test stand to break in the cam. I am at the point of filling with distilled water (our tap water has tons of solids in it) and checking for leaks before priming oil pump, putting on headers, etc. I didn't want to yank the water pump and pulleys off the car just to break the new engine in on the test stand so I picked up a ProForm electric water pump that I hoped to sell on Ebay after the break in.

A couple days ago, I had everything sealed up, started adding water and it was leaking at the passenger side of the water pump where it meets the block. I had put black rtv on the gaskets and bolts before assembly, so I couldn't figure what was wrong, so I pulled it back off, cleaned up the surfaces, checked for flatness of the surfaces and everything looked fine, so on went new gaskets & rtv. let it set overnight, tried filling with water and again it started leaking. I did double check, the timing cover and it's gasket is not interfering.

Today, I took the water pump back off, took it into my kitchen (dont' tell my wife) and on the flat formica I put some 220 grit wet sandpaper then cleaned up the surfaces of the flanges. Everything looks great.
Double checked the surface of the block and as best I can tell, looks dead flat. So again I had 1 more pair of gaskets. Same thing...slight trickle out of between the water pump flange and the block towards the lower bolt. It is not coming out of the bolt hole. This time I also put on a little more rtv to be sure.

So off it came again. I've cleaned up the flanges, took a yellow highlighter and a uv flashlight trying to spot any cracks in either flange, but I can detect none. I plan on hitting the local auto parts store to see if they have any actual uv dye and try that, but a regular highlighter actually works very well.

All times I had torqued the bolts to 25ft/lbs. The last time I installed the pump, I barely snugged it up and let it sit for about 6 hours before I torqued it down.

I've installed several sbc water pumps and have never ran across anything like this. I do have my old L98 water pump that I could install just to see if it seals up. I wouldn't be able to use that for the break in due to no pulleys (and it's reverse rotation and a regular pulley would be clockwise.)

Any ideas would be appreciated.

Thanks,

Carl

Edit: Forgot to mention, it's a plain old SBC, not LT1, etc.

65Z01

Might be worth a shot with the old WP since you know it sealed on the L98. If still leaking it pinpoints the issue to the block.

BTW, I prefer Permatex non-hardening sealer for such an ap, both on the gasket and bolt threads. Never had any leaks with it and don't need to let it set up for >24hrs as with the RTV.

cohocarl

Thanks, I'll pick some of that up while I'm getting more gaskets...

cohocarl

Well, good news...(hopefully)

I thought I'd wire brush off the bolts and run a tap through the threads in the block to get off the old rtv. While cleaning off the bolts, I noticed one of the bolts on the passenger side (where the leak was) had it's threads flattened out at the end. I had noticed it came back out fairly stiff, but I thought it was the dried rtv on the threads.

It appears the bolt was bottoming out on something in the lower hole of the block where the leak was. I measured the depth left on the bolt when it starts to feel bottomed out (around .600"), and the width of the water pump flange (around .525"), and even adding in the width of the gasket, I think it felt like the bolt was torquing down correctly, but really wasn't. I measured the bolts and they have 1 1/2" of thread, so I may pick up some 1 1/4" and try those.

Did not have enough time to get it back together yet tonight, but I'll try stacking a few extra washers on the bolt to see if it seals up. I sure hope that was the problem....and not a cracked block.

Sorry for the poor pics.