PLEASE HELP! What is this renegade bolt
 

After finishing my coolant flush and re-mounting the two belly pans I found to my shock a big bolt on the garage floor under the engine area. The hex bolt is about 1 1/2 inches with the head 1/2 inch in diameter and thread diameter is 1/4 inch as in the picture.

When I found it the car was still on jack stands and I was lying on my back under the car, so that no other action could introduce it from elsewhere.

I certainly did not touch such a bolt during my coolant R&R and I did not hear or see it fall down. My infinite worry is where it's come from. Such a big bolt when lost is no minor matter.
I'd appreciate if you can identify it. Thanks a lot!

http://s787.photobucket.com/albums/y...Picture001.jpg

Maybe a distributor clamp screw?

Probably something dropped and lost years ago and replaced at the time.

Given this is a Mercedes, "distributor clamp screw" is a pretty funny guess.

I hope it is like you said. It is almost like a surgeon finding some extra part after sewing up the patient :(

MB parts are metric. Use the other side of your ruler:)

If the bolt diameter is 8mm and the hex size is 8 or 10mm, looks like a motor mount bolt to me. So, I rec you check them.

I took a look and found a lot of engine components which use similar hex bolt and the water pump is one of them. Others are intake manifold, the silver block under the water pump.

The problem is I see no hole, which misses a bolt, and no loose part when shaking. Of course without a lift to investigate from under it is difficult to see.

My indy replaced the water pump last year in August.

I think the plastic pan has to come off the check the lower motor mount bolts. You can see the upper ones looking in from the topside.

Since the water pump is the main suspect I am going to watch for coolant leak. Other than that it is pointless to guess the location of the renegade bolt, since it is nothing particular but is used in so many parts.

Thanks for all inputs.

That's what my distributor hold down bolt looks like... Of course, I have a lot of allen heads on my engine where EPC shows hex heads.

Granted, if that's what it was, you'd know it pretty quick.

I checked the motor mount bolts, both are still there and they are not hex bolts but the kind of bolts you need a socket, probably 13mm, to deal with.

Thanks for your hint, at least I am sure that engine mounts are OK :)

when it rains it pours!
I jacked up the car and got myself underneath again and found ... not one but two candidates for the bolt :(
The first location is probably the water pump, but I cannot identify the second part. Lacking knowledge I went with my guts feeling and decided for the location one. Am I in luck?

It is claustrophobic under the car!
Location 1 (two pictures, the second one with the bolt inserted)
http://s787.photobucket.com/albums/y...Picture008.jpg
http://s787.photobucket.com/albums/y...Picture009.jpg

Location 2: no idea what it is, between engine and tranny.
http://s787.photobucket.com/albums/y...Picture010.jpg
http://s787.photobucket.com/albums/y...Picture011.jpg

Hex vs. Socket
 

The bolt you found is a socket head. A hex head bolt has a head in the shape of a hexagon - the kind you'd use a socket on. Best of luck with the search, though.

Jay

That second hole you pictured is likely an unused mounting hole on your car....

renegade bolt
 

texholdem. I am in Dallas. I own a 300E. contact me @ rickkhall@yahoo.com

first off, don't worry. If nothing's visibly loose, you're not going to loose anything any time soon.

You'd prefer not to be missing an accessory bolt, but it's not unheard of.

Just put it back and torque it down. Do be careful about where you put it, try and make sure it actuall is the right length for the hole you're screwing it into.

Over torquing a bolt or worse, bottoming out in a blind hole are not good things to do.

HTH -CTH