17 mm Bolt Through Water Pump

[moe2100]

Hello,

This is my first post and this forum has been incredibly helpful since I purchased my E30 two weeks ago, I have found a solution to every single issue I have encountered except this one. The previous owner for whatever reason decided that a 17 mm bolt would be more appropriate than the 13 mm bolt that secure the top of the water pump to the block. I am not sure how they even managed to fit it in there since there was no clearance for a socket and I had to use an angle grinder to make room for a wrench. What would you guys recommend doing in this situation? Can I get away with using just the bottom two bolts and maybe some RTV, or should I reuse that 17 mm bolt and just grind a notch in the new water pump.

[e30davie]

That bolt is a standard 8.8 so arguably the biggest head avaiable for that size thread.

Is there still a good thread in the block?

If so I would find the same threaded again but in something with a smaller head. Even a socket head capscrew with internal hex would work too. or there are Japanese standard bolts that have a smaller head.

[tomstin]

Another thought would use a heli-coil and bring it back to 13mm

[Northern]

+1 to a SHCS, or some sort of thread insert if they didn't drag the hole when they drilled it *and* you think it will sit flush and seal.

[moe2100]

+1 to a SHCS, or some sort of thread insert if they didn't drag the hole when they drilled it *and* you think it will sit flush and seal.

The previous bolt was just forced into the block creating a new thread which is on a slight angle going in and the threads are a little inconsistent. I think I will try a SHCS and see if that feels tight before using a helicoil. Between these two options which one would do you think would provide a better seal. Also someone messaged me telling me to take it to a machine shop and have them weld and retap it, but that sounds a little expensive and I hope one of these two methods work.

[cory58]

If you can run a tap into the hole and create some decent threads for the 17mm, try that. A helicoil that depth won't have too many threads to hold it in the block, but would be a good plan B.