SweetBadger 94 Posted April 30, 2006 Following on from my disaster last week where I found that one of the rods in my rebuilt MI was buggered, I got to putting a new rod in and bolting the bottom end back together yesterday. Anyway whilst tightening one of the sump bolts it started to get prematurely tight, so I pulled it back out, and with it came a plug of old silicone sealant. Problem solved I thought and put it back in... When it was close to being fully tightened it got a little tight again but I carried on going thinking it was a bit of sealant in the threads, a couple of turns later ant the bloody thing exploded! I mean literally there was a bang and a flash from the end of the bolt! Scared the sh*t out of me! Having checked everything over all is still intact (was half expecting a chunk of block to be missing) and the sump bolt goes in no problem. Any ideas what caused this? I'm no chemistry expert but my theory is that as I tightened the bolt up it created a seal which compressed some sealant in the bolt hole. The sealent or whatever it was in the hole must have become unstable as it was compressed- hit flash point and exploded...Weird! Anyone ever heard of anything like this happening or have a better explaination? Share this post Link to post Share on other sites
Wurzel 16 Posted April 30, 2006 I know that hydraulic locks like this can bust holes in blocks etc. Where abouts was the bolt in relation to the starter motor or alternator. Share this post Link to post Share on other sites
Guest Cartooner Posted April 30, 2006 (edited) I think it's a very plausible solution. Diesel fuel ignites when compressed, so I don't see why a silicon, which must contain various flamable ingredients could not react the same way. By compressing it You introduce heat which might make it unstable to the point of selfcombustion. The bolt did unscrew (very rapidly) I presume because there is no damage? You're lucky the block didn't crack and You did not get hurt. Edited April 30, 2006 by Cartooner Share this post Link to post Share on other sites
SweetBadger 94 Posted April 30, 2006 I know that hydraulic locks like this can bust holes in blocks etc. Where abouts was the bolt in relation to the starter motor or alternator. The bolt was at the flywheel end next to the ones that go into the main bearing cap (see pic). It's a preety chunky bit of the block so I think it's ok - I can only see inside the block because the gearbox and flywheel are in the way, but there's no crack to be seen. I might try and put some water down the hole under pressure tomorrow to make sure there's no crack... I think it's a very plausible solution. Diesel fuel ignites when compressed, so I don't see why a silicon, which must contain various flamable ingredients could not react the same way. By compressing it You introduce heat which might make it unstable to the point of selfcombustion. The bolt did unscrew (very rapidly) I presume because there is no damage? You're lucky the block didn't crack and You did not get hurt. The bolt didn't actually come out (thankfully as I'd have been right in its way!) I think from what I saw that the explosion blew its way past the seal created by the thread and the gas and small spark came out past the bolt head... Share this post Link to post Share on other sites
