Stripped caliper bolts.

Doncha just love a routine job that turns into a 4 figure nightmare? Bought new pads and shoes for the rear wheels of my 98 carrera 2 cab and gave to my trusted mechanic to fit. Unfortunately, the caliper mounting bolts had fused into the hub carriers resulting in stripped threads. The outcome is 2 new hub carriers with discs, bearings etc (no point replacing old stuff since I track day the car) with a bill for parts alone hitting 4 figures. The lesson? Check your caliper mounting bolts (there's only 2 per side) and make sure you can get them out. Then copperslip the threads to prevent corrosion/fusion.

These things happen but I alwasy console myself by telling my self the money I have saved doing things myself successfully easily outstrips the cost of the occational professional help and you got new bearings, etc So another job done! I try to never put a bolt in dry, copperslip, grease or locktight. Mav

I had exactly the same happen to mine - yes it is expensive! Even more annoying was the fact that if the damn dealer had put copper slip down the threads it wouldn't have happened - now I wonder why they would do that???

A bit late but something for future reference. I tried out a new product from our local paint merchants it's a liquid spray that is at -47, you spray it on a seized bolt for 10 seconds, leave it to work for a few minutes and hey presto no more seized bolt. I have used heat before to get bolts undone and this must work in the same way just opposite (if that makes sense). I wasn't convinced when I brought it but I have used it several times and it works without all the potential burn damager a blow torch can do! Mav

Interesting. Whats this stuff called?

Simon Copperslip - PBC [ Polybutylcuprysil ] High Temperature Grease. EG Unipart GAC 132. Although I would generally agree with previous comments, regarding the use of this product, I wouldn'y necessarily advise it's use in all applications, but always be guided by the manufactures assembly notes, particularly where nut / bolt torque figures are quoted. The requirement might be to assemble dry, lubricated, thread-locked, greased ........... R.

Richard I think Simon meant what is the freezing agent called. I'd be interested too.

I had the same thing happen while it was with the OPC for new discs/pads.They charged me £55 for a precision engineer to get them out. Not too bad I thought.

If you are a bit handy you can use a Helicoil or Recoil insert, which basically means you drill out the old thread, cut in a new thread and insert a spiral wound stainless steel thread. Meant to be stronger than the original where aluminiun is concerned due to the larger area the force is spread over. Costs about £40 for a set.

I discussed helicoiling with my mechanic and he felt that this would not be a cost effective solution nor ideal given the fact that I track the car occasionally. I agree, with brakes you need to have absolute peace of mind so I would go for new parts where any failure has occurred.

I think the stuff your looking for is "Loctite Freeze And Release" or in the trade it may be refered to by it's Loctite part number 8040 It's about £5 a tin How it works from Loctite's web site:- LOCTITE® 8040â„¢ is a special mineral oil formulation to free rusted, corroded and seized parts. The shock-freezing effect will cool parts instantly down to -43 °C and cause microscopic cracks in the layer of rust. This allows the lubricating ingredients to wick directly into the rust by capillary action. Released parts remain lubricated and protected from corrosion.

Discussed the use of Freeze and Release with my mechanic. He wouldn't touch the stuff for this application. In his experience, the thermal shock degrades the metal of the thread which becomes crumbly over time. Not too worrisome if its an exhaust clamp but not what you want for a brake caliper bolt. He has mechanicked for privateer porsche entries at Le Mans so I think he knows his onions.

Richard [Hamilton] Oh! Well, Simon has the assembly and disassembly information now! R.

Helicoil/Recoil type inserts are used a lot in the Aviation industry where high strength is required in the design of steel to aluminium interface with threaded components so I wouldn't worry about strength issues if they are inserted correctly. Many aluminium blocks/cylinder heads have steel connectors fastened with inserts due to the stronger joint. The Porsche bolts are rumoured to have a coating to prevent bimetal corrosion but the only reference in the workshop manual is that bolts for different models of 996 (C2/4, GT3 Mk1/Mk2/RS) are painted different colours for identification purposes as they are different lengths. The manual says they must be replaced whenever removed. Some people think this is because they are 'stretch' bolts but for the size of them compared to the torque applied they are definately NOT stretch bolts, so perhaps the 'special coating' rumours are true. The manual does not mention using aluslip or coppaslip. There is a wide diffence of opinion as to whether this sort of product should be used in this application as lubricated bolts will torque up higher than non-lubed bolts due to the reduced friction between the contact surfaces. If the manual gives dry torque figures then that is what you should really do. A lot of people do however re-use these expensive bolts with application of loctite or coppa/aluslip without problems though. On both my old C4 and my current GT3 when I have removed the bolts when swapping discs, they showed the use of coppaslip, and both had been maintained by OPC's. They are very easy to strip so just be very careful if you DIY and do not over torque.