Uneven bolt hole on water pump housing/assembly

The other day I noticed a coolant leak on my serpentine belt. I assumed it was the water pump. Upon installing a new pump a pair of the bolts would not simply hand tighten down. I went in with a chaser tap to fix the threads. Problem now is that someone who previously “fixed” this apparently tapped one of the holes incorrectly (I’m thinking they over tightened then tried to tap new threads but didn’t make it perpendicular). So now this bottom left bolt hole is off and the bolt won’t sit flush. I’m trying to figure a way to keep this from leaking (Whomever did this previously was able to accomplish this) without pulling out the housing/assembly and retapping/helicoil etc. I will later go in and learn to do this etc but I currently don’t have the time to learn how to properly do it (also have registration due soon/smog).

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95 Buick Century 3100 SFI v6 3.1

Best bet, take the vehicle to an auto machine shop. They’ll have the equipment needed to fix that problem. The only other possibility is that sometimes the bolts that hold the water pump etc are different length for the different positions. That’s certainly true for my Ford truck. IIRC on my truck there’s 7 bolts for the water pump and 4-5 are different from each other and different from the others. It can be a puzzle determining which bolt goes where on the install unless I remember to make a sketch as they come out. So start off by double check you are putting the bolts in the same hole you took them out.

Thanks for the reply. I tried looking at the oem bolts for it and they are m6 x 1x 16 (also compared all the bolts) so they should all be the same size for my particular car. Yeah I’m planning to do a more permanent fix later ie machine shop or trying to helicoil it myself. I just need a temp solution for now. I was thinking about using a washer and some sealant on the bad hole.

It’s worth a try I guess. You’ll probably get the best chance of success if you drain the cooling system then give the sealant some time to set up before refilling & driving the car, maybe 36 hours. I fixed a problem with my kitchen sink drain that way, the correct solution was to install a new strainer, but too much work, so I did a work-a-round with sealant, still holding … lol …

Yeah everything is already drained I’ve just been trying to decide to try something like this temp fix or go to a junkyard to look for the housing (also to figure out how to disassemble everything). I assume gasket sealant should work but not sure if there is something more specific to use.

Some friendly advice, if this is a car you plan on keeping for some time, just bite the bullet and fix it correctly, either the junkyard part replacement or the machine shop idea should work. If the coolant leaks out all of a sudden while driving and you don’t realize it the engine will be toast. All you’ll have is a big lump of metal in the engine compartment, all the internal moving parts no longer moving. Too much risk compared to just solving the problem correctly imo, a problem you have to solve eventually anyway. If you don’t have the needed diagrams and procedures for this car, take a visit to your local public library, they may be able to offer assistance on finding the info you need there.

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Yeah I def. hear your advice. When I say temp solution. I simply wanna be able to get a smog for registration. Basically drive it 30 mins so I don’t have to deal with moving permits or late fees etc. I already have a lot on my plate (Father passed recently, dealing with aftermath, career transition etc). I def. appreciate the advice though.

replacing the timing cover might be quicker and cheaper than having a machine shop repair the damage


How about some sort of flexible washer under the bolt head? Wander an aisle in the plumbing section of a hardware store for a nice thick washer.

Thanks for the replies. I’ll def. look/consider just buying the timing cover. Process didn’t look too complicated when I looked at a video online but they also changed the intake gasket so the video mostly skipped the timing cover gasket change. I’ve gotten a few different opinions on using a washer to try to hold it. Wentwest you suggested a thick flexible washer, others have suggested a flat washer with sealant to the bolt, and another was to add a flat washer then a lock-washer. Any opinions on why one option is more preferable to another?

I guess I am confused. Wondering if you loosened the other 3 bolts, could get enough wiggle room to get all four bolts to go, then torque as needed. It looks like you tightened down 3 bolts and the fourth was off, which would not be the proper thing for that, just my thoughts. It fit before, why not now?

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I think the issue is the bolt is in there crooked (in the hole at an angle). If it’ll tighten the pump against the gasket and timing cover, I don’t think it’ll leak anyway, though. I’d use a little rtv on the gasket and a flat steel washer on the bolt if I wanted to do a quick fix. I think that would be fine.

There are actually 5 bolts holding it down 12, 2, 5, 7, and 10 o’clock. The one at 7 is the one that won’t sit flush. The original issue is that there was a large leak onto the serpentine belt. I assumed it was the water pump. I simply tested by putting on the pump before adding the sealant and gasket. That is when I noticed the off bolt. I’m trying to find a solution that won’t allow a leak after letting it sit for 24-36 hrs (that would be quite a pain). The leak might have just been from the water pump going bad, the gasket going bad, or the issue related to the bad hole.

I have used this on wood screw stripped holes as a thought. https://images.homedepot-static.com/productImages/0cc20cb2-19f5-40e1-a880-04ec04580c94/svn/everbilt-specialty-hardware-801724-64_1000.jpg

Yeah that’s what I’m thinking too john. That is my current short term plan. Just trying to get opinions now on the three differing opinions to use flat washer with sealant to bolt (yours of with no mention of sealant to washer+ bolt), flat washer with lock washer (so together) and wentwest’s suggestion of thick flexible washer.

Thank for the link Barkydog I’ll look into that product.

If you use rtv on the pump and/or gasket surface (I’m assuming it’s a flat paper style gasket), I don’t think you’ll need additional rtv on the bolt. You might put that problem bolt in last and put a little rtv in the bolt hole first, just for good measure. The washer is more to keep from damaging the face of the water pump than anything else, in my mind. Will keep the edge of the bolt head from digging into the alum pump.

If the gasket is the rubber o-ring style, I would not put rtv anywhere and I don’t think you’d have a chance for a leak. I’d just use the washer and bolt.

Yeah it’s a flat paper style gasket. I have some red rtv. I’m now thinking it might be better to try without the rtv in the hole (for cleaning purposes if it doesn’t work).

Check the housing to make sure it is not warped, my thought.

Yeah the housing looks fine. I haven’t messed with it. I’ve had the car for years and haven’t recently had any leaks in the area (only at the radiator).