924Board.org

Rakom · Joined: 21 Jul 2012 Posts: 4 Location: Italy

Hi, I'm new to this forum!

I'm trying to bring back to life a 1981 924 turbo, but i have a problem with the thermostatic valve housing screws.

I was trying to get the housing down from the engine, but during the process two screws broke, and now i can't take them out.
They broke very precisely, and without applying a lot of force, just like they were made of aluminium...
I've tried to take them out with a parrot pliers (don't know if it's the right term, i mean this:

) with no positive resoults....
I've also sprayed it with WD40 and other products (penlube and svitol), but again no resoults.
Also, it's impossible to drill and use a reverse extractor without taking out the engine, and i would like to avoid it if possible.

Don't know if it is relevant, but the car has never been turned on in around 3 years.

What can I do?

Here some photos to see the problem
https://lh5.googleusercontent.com/-wzj3tCruA7A/UAqqB5bey7I/AAAAAAAAAHQ/n_D79KjHqMg/s1068/P1070372.JPG
https://lh5.googleusercontent.com/-tmksJGYa-84/UAqp3E3jY-I/AAAAAAAAAGw/6engFZLg3kM/s1068/P1070368.JPG
https://lh4.googleusercontent.com/-b8SahyE_pO8/UAqp8UeVKpI/AAAAAAAAAHA/WG7nsj5uy0Q/s1068/P1070370.JPG
https://lh3.googleusercontent.com/--pggI_JH60k/UAqp7qb9S_I/AAAAAAAAAG4/HKbrpMffw24/s1068/P1070369.JPG

!tom · Posted: Sun Jul 22, 2012 7:56 am Post subject:

The aluminum in the head has oxidized which is causing the problem. The aluminum oxide increases in volume, which causes the threads to seize.

A technique that can work well in this situation is to take a couple nuts (one per bolt), and weld the nut to the end of the stud.

This does two things.

The heat from welding can help break the bond between the stud and the head
You now have a new head on the bolt that you can turn with proper tools

Recall also that aluminum has a much higher coefficient of thermal expansion than steel. If you can heat the area to a high temperature (up to around 200 degrees C), the bolts should be easier to remove.

Clean out the threads with a tap and use anti-seize on reassembly!
_________________
78 924 NA
5-lug

Rakom · Joined: 21 Jul 2012 Posts: 4 Location: Italy

thanks very much for the advices!!!

I've got a heat gun, and a welder too, so i'll try as soon as possible.

Another doubt... a pneumatic wrench would be better than a normal wrench to take out these screws?

emoore924 · Joined: 13 Apr 2004 Posts: 2822

I think a pneumatic wrench would make the problem worse -- less control over what's going on with the extraction and more likely to snap off flush with the head. A heat gun will heat up everything, not just the broken-off stud. So I would not try that.

The "weld the nut on" approach may work best if for no other reason that you'll shock what's left of the bolt with the heat. A propane torch may do the same thing. And/or add a couple of sharp raps with a brass or ball-pein hammer. You might also try to double-nut it if the threads are still there.

Take your time. What's left will come out.

!tom · Posted: Mon Jul 23, 2012 12:03 am Post subject:

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Heat the area with a torch, then spray the stud with a cold spray, follow immediately with PB Blaster or Kroil (WD-40 doesn't count). Repeat a few times and you'll break up the corrosion enough to get it out.

The heat will expand the metal, while the cold will contract it and help wick the corrosion dissolving solution into the threads. Repeating a few times will ensure you let the procedure work properly.

Be careful with the torch and the sprays, etc. most are flammable.

Good luck!
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Rakom · Joined: 21 Jul 2012 Posts: 4 Location: Italy

I've got the torch too, so i'll try first to weld a new head to the bolt, and see if i can pull it out, in case of failure I'll use the torch to heat the zone.

As soon as it stops raining...

chrisvs · Joined: 26 Jun 2012 Posts: 25 Location: North Bay, Ontario

I just went through this on the weekend as well. What I did was drill out the rest of the bolts, then through bolted the housing and cap with a nut and bolt. I really don't like the design of threading a piece of aluminum, then bolting into it with steel bolts. I know it is done all the time, but it seems to me that through bolting is a better way where it can be done. I wont deny that it is a bugger to get the nut under the housing on the far side, but if you take the boot to the throttle body off, you can get at it with a wrench.

Steel bolts in aluminum.... blech!!!!

_________________
1978 924 4-spd

Rakom · Joined: 21 Jul 2012 Posts: 4 Location: Italy

One Bolt is out!
But the other broke during the process... it's still long enough to weld a short nut, but I am not really skilled in welding... hope i can do it, it will save me lots of trouble...

Here a photo

As it made the first turn to unscrew, it became loose (ok, a little bit more loose, not completely) an it came out.
Great victory.

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Keep at it, Rakom!

The welding doesn't have to look pretty.

Put plently of weld on. This will (a) put more heat in the joint which will help loosen it as stated earlier and (b) give a good strong grip on the bolt for getting it out.

Slowly and carefully, you 'll get there!
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org