cantab27

hi all, well after putting a second hand trans in + front wheel bearings +output seal, i am now stumped on this little problem....have snapped the three bolts on the drivers side engine mount....they have shared off in the block and cant get a start on them..have tried the right hand drill bit, the air grinder with drill bit but still no go..now I'm thinking should i take guard off and cut hole in the inner guard and get a long drill going because if that don't work i think i might have to pull the engine, and i really don't want to do that..its the smallest thing i have broke but proving to be the hardest.....any ideas..... the kiwi

stoneattic

I was able to get mine out with one of these:

http://www.tylertool.com/milwaukee55..._source=nextag

Mine's is the older style drill but it worked. I had to unbolt both mounts and raise the engine a bit too. I used a left handed bit and that backed two of the three out. The last one I had to drill and tap.

I replaced them with grade 8 bolts and had them break a year later. I then replaced them with Unbrako socket heads with a flat washer and a split lock washer thinking that maybe them were coming loose and being "hammered" until they failed. The Unbrako has a higher tensile strength than grade 8. I also switched to MORE mounts. That has held up for the last 5 or so years. I'm not sure what made the difference though.

5-90

It's a known problem that some of the engine mount screw holes aren't drilled & tapped deep enough - the techs will talk about it off the record, but you'll never get anyone important to admit to it.

Check the new screws as you torque the first one down - if the underside of the head doesn't contact the mount bracket, it's bottomed out and it will fail again!

The fix? It's easy - stack a couple of flat washers under the head. Stoneattic - it's the washers that are saving you (nothing whatever against SPS/Unbrako - I love their hardware, and wish I had a local source! But, whenever I've heard about engine mount screws failing, it's been because they've bottomed out in the hole, not because they were weak and just failed.)

stoneattic

The one thing that makes me question (not dispute) the too shallow bolt hole theory is how easily two of the broken bolts backed out when I hit them with a left handed drill bit.

I've also heard people suggest that the bolt holes aren't perpendicular to the boss surface thus side loading/twisting the bolt heads. I've also heard that perhaps they are just coming loose and the mount bracket moving is causing them to be hammered/impact fatigued until they fail.

Of course I threw everything I could think of at the problem the second time because I don't want to have to deal with drilling them out again.

So far, so good.

5-90

The "screws bottoming out" isn't the sole cause of screw failure - there's also shonky materials, counterfeit screws, screws losing torque, and a host of others. You're certainly right to be sceptical, since there's more than one explanation.

However, bear in mind that if you're torquing against the bottom of the hole (instead of the underside of the head,) it's also more likely that the screw will work loose anyhow - which could make it back out quite easily, and lose preload (thereby losing hold and failing due to repeated stress/strain.)

I'm not trying to tell you what happened - just giving you the most likely scenario. Hell, I could be wrong - it's happened before!

However, I'm just convinced enough that, when I had to replace my mount cushions; I also pulled the screws, replaced them outright (using quality socket heads,) and installed two flat washers under each head (using LocTite #242 to retain them. I never did like split lockwashers.) Haven't had any trouble since, touch wood.

cantab27

[URL]http://www.tylertool.com/milwaukee55.html?
that would work, cool wee tool..now just have to find one over here...as for how they broke, well lets just say there was a bit of air , nice take off ,**** landing.... also bent some other stuff as well, nothing major but....thanks

stoneattic

I felt that if they had bottomed out against the bottom of the hole that they would not have backed out so easily with the left handed drill bit. But like you said it could easily have been a combination of things.

I thought about LocTite as well but did like the thought of them breaking again and having them LocTited when I tried to remove the broken peices.

I'm also not a fan of lock washers in general since they seem to loose their tension with time, but they seemed like they would be better than nothing.

matejcekautoworks

why in the world did u pull the engine mount off in the first place?

stoneattic

The bolts broke on their own, as 5-90 stated, a known problem. It's more prevalent on certain years, 94-96 if I remember correctly, but don't quote me on the years. Check the NHTSA site and search for it, you'll find plenty of complaints.

trans_am7935

so when i eventually do get these things out, should i use lock tight on the bolts? also is it a wise thing to change the passenger side bolts as well just to be safe, i mean this thing takes quite a beating and i cant have this happening again.