Valve cover stud stuck, need help! - PeachParts Mercedes-Benz Forum

jam9297 · #1 01-31-2015, 01:29 AM

So I bought my first 300D a couple weeks ago, the paints in rough shape but everything else is in good condition. Now I know these old diesels are notorious for leaking(not a serious leak, just a drop here and there is all i'm saying). Anyways, this one had a visible leak from the gasket area and i'm guessing it wasn't taken care of very well by the PO(I made sure the cover and head were straight and they are). I figured I'd change the oil, adjust the valves and then lastly put on a new valve cover gasket and it'd be ready to cruise. I got through the first two things no problem, but when putting the valve cover back on, I noticed the rear valve cover stud closest to the passenger side was pretty badly stripped(the other 3 are good, but I did notice this one came off unusually easy and I figured it had to do with the low torque spec. for the nut but I guess not). I have tried vice grips, pb blaster, welding a nut on and using a socket to get it off(weld broke) etc. but these haven't worked yet. I'm unscrewing it CCW and the stud is most likely original since I managed to bend a pair of good locking pliers trying to unscrew it. I heated the stud up and bent the top over in an effort to give the pliers something better to grip onto(I used a heat shield to protect areas around the top of the stud) but I still wasn't able to unscrew it - the pliers gave way first. I'd hate to take this thing into a shop/dealer, but if they were presented with a situation like this, what do you think they would use to get this thing out? Thanks for the help/suggestions, -John

vstech · #2 01-31-2015, 09:48 AM

My guess is the stud is installed with loctite. I recommend you consult the fsm (startek.com free access) and see if there is a section on prep for stud removal. The head may need to be heated to get the bolt out.

Stretch · #3 01-31-2015, 10:01 AM

Quote:

Originally Posted by vstech

My guess is the stud is installed with loctite. I recommend you consult the fsm (startek.com free access) and see if there is a section on prep for stud removal. The head may need to be heated to get the bolt out.

Nothing in the FSM that I know of for those little studs.

I'd be wary of heating up any localised area of a head (even if it is a cast iron lump) - but you might not have a choice.

Seeing that the damage has been done I think the only way forward is to be persistent with the extraction of that damaged stud.

I recommend removal of the rocker arm towers close to the stud so more purchase can be achieved.

Here's the chapter for rocker arm removal in the FSM =>

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/617/05-235.pdf

JVCinSC · #4 01-31-2015, 12:05 PM

Something so small can become quite significant! Right when I think I have some dilemma with my car I read something like jam9297's problem and I count my blessings. As Stretch said, I'd be wary of heating up a localized area on the head for fear of creating a bigger problem than I already had. At the same time I have no advice to give as it seems you've tried everything commonly used to remove that stud. It may be time for professional help. PITA I know but a warped, cracked or damaged cylinder head would be worse than the victory of getting the stud removed by whatever means was necessary.

Good luck. Can't wait to hear the ending of this story.

leathermang · #5 01-31-2015, 12:14 PM

Listen to Stretch about not heating the head.... cast iron is strong... but can crack due to uneven cooling...and if you have uneven heating... localized... you by definition have uneven cooling..
I would suspect corrosion before Locktite...as even RED stud and bearing mount...on a bolt that size only adds about five foot lbs of torque to undo it...
You have been doing all the usual correct things... except I worry about ' the weld broke'... if that is really what happened.... as compared to the bolt breaking.. so if you can retry that... use HIGH ALLOY ROD.....and try again.. welding a nut around a broken bolt sure has a high success rate around here... not only does it hold the bolt .. but also heats it really well... giving the chance that the expansion of the bolt will crush any corrosion at the threads... then when it cools.... leaves some clearance to let it come out...
I can not tell how much space you have... but there is a tool called a stud remover.. which has an off center moveable center which provides a large grasp on the stud and grips tighter the more grip is needed....
If you try the nut welded over the bolt.... file out the threads of the nut you are going to use...and find a grade 8 nut also....

funola · #6 01-31-2015, 12:55 PM

If it's Loctite that's holding it, heating the stud base with a propane torch to 500F (softening point of Loctite) should not cause damage to the head.

If you can get a small pipe wrench on the stud, that will grip much better than Vise-grips. I have a 6" pipe wrench and a 18" pipe for leverage for ***** like this and it's saved my butt quite a few times.

leathermang · #7 01-31-2015, 01:53 PM

This works in tighter spaces than a pipe wrench...but still requires more room than welding a nut around the stud or broken bolt...

Stud Extractor Tool from Sears.com

vstech · #8 01-31-2015, 02:12 PM

I have successfully welded fresh metal onto bolts and ground round and rethreaded... but not on a head...

TnBob · #9 01-31-2015, 07:40 PM

Id sure like to know what the yellow stuff is around the stud.
The basics, Kroil penetrating spray works wonders.
Need to try even a 4 or 6" pipe wrench and TIGHTEN the stud even a 1/16th turn.
That should help break it loose. The pipe wrench teeth also bite as you start to turn.
Those studs should come out very easily.

jam9297 · #10 02-02-2015, 12:33 AM

Quote:

Originally Posted by JVCinSC

Something so small can become quite significant! Right when I think I have some dilemma with my car I read something like jam9297's problem and I count my blessings. As Stretch said, I'd be wary of heating up a localized area on the head for fear of creating a bigger problem than I already had. At the same time I have no advice to give as it seems you've tried everything commonly used to remove that stud. It may be time for professional help. PITA I know but a warped, cracked or damaged cylinder head would be worse than the victory of getting the stud removed by whatever means was necessary.

Good luck. Can't wait to hear the ending of this story.

Turns out it ended way better than I expected, and I think I may have inadvertently invented a new way to remove stuck studs(or maybe even rounded-off bolts too

). So what I did after thinking about this for a while was I got an E12 socket, a torch and a hammer(yes, I know it sounds crude but given the fact that the soft metal would absorb most of the shock, I wasn't too worried). I heated up the top of the stud(while using a heat shield to protect adjacent components) and when it was about red hot I took the torch and heat shield off and put the socket on the stud with a 6" long 3/8" ratchet extension and began hammering. It took some good blows to get it on, and when I tried to get it off(The socket wasn't supposed to stick on in my plan), it wasn't budging. So I figured I'd try and unscrew it with my jury-rigged train ratchet and what do you know? It worked haha. The stud sort of grew it's own teeth to grip onto the socket and this method works especially well in tight places too; The space I had to work in was probably 2 inches(maybe more but it sure seemed small). And contrary to what I thought, removing the stud from the socket wasn't very difficult; I just put the socket in a vise and punched the stud out with a screwdriver. Thanks for the help and replies everyone, the diesel can now go back into service!