Bolt that Holds Belt Tensioner Shock to Head Snapped Off

[SimplyThinkDreams]

Greetings!

I recently discovered that the bolt holding the left belt tensioner shock to the head snapped off on a 92 300D. Currently, the only tension on the belt is being provided by the tension spring.

The problem is that the bold snapped off inside the head so I cannot weld anything to the remainder of the bolt; and, there is not enough room to drill it out and tap it without removing the radiator and fan shroud, which I really do not want to do.

I was wondering if anyone knows if the said bolt protrudes into the inside of the head itself - the right hand side of the "L"? If it does, I was thinking I may be able to remove it from the inside or turn it out enough to get a hold of it on the outside of the head.

I wanted to ask on here if anyone knows before I go removing the crossover pipe and the valve cover. I would hate to remove them and find that I cannot access the broken bolt.

I'm usually pretty good at removing broken bolts; and, this would be easy if it weren't for the fact that it is a very tight location without removing the radiator, fan shroud, etc.

Thanks!

[jt20]

I am pretty sure it does not have an open back to the timing cavity where the chain is.

easiest next step I can think of is to shape a nail punch (or any hardened steel rod) into a cone with a point. about 60 to 45 degrees at the tip.

drive that gently into the outer edge of the bolt to make an indent. use that indent to keep the driver set in the bolt

tap the driver in the direction of removing the bolt. go slow. slowly change your angle from parallel to 'closer to perpendicular' to the bolt as you begin tapping.

[Jeremy5848]

Based on a review of my pictures of a 603 engine I once owned, which is very similar to the 602 engine in the OP's car, I agree with jt20 that the shock's bolt hole does not open into the timing chain cavity.

Jeremy

[pwogaman]

I respectfully disagree with you Jeremy. The bolt hole does go all the way through the cover on both the new and old design. This is additionally the same cover for the 603 and 602 engines.

Look through these pictures here :
Index of /images/OM603_timing_cover

[babymog]

The upper belt-tensioner shock bolt is a blind hole into the head approx. .875"/22mm deep, not a through-hole. I removed the bolt on an engine (603 w/ later head) today to check.

[pwogaman]

Originally Posted by babymog

The upper belt-tensioner shock bolt is a blind hole into the head approx. .875"/22mm deep, not a through-hole. I removed the bolt on an engine (603 w/ later head) today to check.

It looks as I misread the problem. I apologize.

[jt20]

Originally Posted by pwogaman

It looks as I misread the problem. I apologize.

when I first read this post, I thought the same thing. "wow, havent seen one of those in while..."

[SimplyThinkDreams]

Thanks everyone for your replies.

A special thanks to babymog for measuring the depth of the bolt hole, which is really useful information!

I figured out how to drill the bolt out and re-tap the hole without having to remove the radiator.

I ended up buying a Ryobi flexible drill extension that can bend up to 90 degrees. The extension accepts hex quarter inch drive bits; so, I also bought a drill bit with the quarter inch hex drive from Home Depot. I bought the tap from a local machine shop.

In order to get access to the snapped bolt to drill it out, all I had to do was to remove the clips that hold on the fan shroud to the radiator. I popped the shroud up enough to slip the flexible drill extension under it. I held the drill bit end in one hand and the drill in the other. I was able to drill it out fairly easily; but was a little off center because I first drilled it in order to use a bolt extractor because I could not find the correct tap at first and thought I would be able to remove it with the bolt extractor. I was wrong.

Anyways, I bumped up to the correct drill bit for the tap and drilled in very carefully because I did not know how thick the wall of the head is and did not want to go all the way through.

After drilling with the bit so far, I ground the tip of the drill bit off to make a flat bit. Then, I drilled out the taper left in the hole from the standard bit shape.

Next, I tapped the hole starting with a pipe tap. Because, I could not find a bottoming tap, I ground the pipe tap down to make a bottoming tap. I finished tapping the hole with the bottoming tap.

I put a new bolt in with a little blue thread locker because I felt my threads might be a little shallow due to a little bit of wobble that is inherent when using a flexible drill extension that is really only meant for driving fasteners, not drilling

Anyways, the bolt went it in and snugged up nicely and my tensioner is working properly again. Hopefully, my drill and tap job will hold up. If not, I guess I could always heli-coil it.

Thanks again everyone for your replies!

[vstech]

The shroud and fan are pretty easy to remove on the 92, I'd pull it, and see if you can fit a drill in there.

I recommend the dewalt 90degree drill adapter, and the set of reverse drill bits found at Home Depot. They work great! And the bolt will not be difficult to remove at all.

[Jeremy5848]

Originally Posted by pwogaman

It looks as I misread the problem. I apologize.

Thank you. I could just as easily have been in error. My pictures were taken as part of a head replacement project and didn't show the upper bolt hole clearly.