FredR

Recently had a problem with ac gas leakage that I traced with my Chinese gas sniffer to the Schrader valve. Revamped my system last cool season but did not change the Schrader valve- lesson learnt!

No big deal really and when I went to set about re-gassing the system the other day I noticed that the belt tensioner pivot bolt and spacer were "missing". Figured i must have forgotten to finish off the tightening correctly - found a spacer and a M8x1.25x 30mm bolt and fitted such with an additional washer to allow for the slightly longer than stock 28mm bolt. The bolt seemed to be taking tension but not fully tight. I then remember feeling a similar sensation whilst fitting the bolt last year so must assume that the threads are damaged. Have not stripped a bolt in over 40 years of messing around with bikes and cars and must assume i am "responsible".

Now i need to find a solution. The more obvious solution is to fit a heli coil or time cert type of approach. Have never needed such previously and looking at youtube vids suggest it is not that difficult- the only problem is that with the radiator and condenser fitted there is about 12 inches of head room to work in.

I thus started to think about possible options and came uop with the following:
1. Heli coil or time cert.
2. Using the remaians of the thread make a stud and Loctite it or bond it in-situ.
3. Make a post with an interference fit and "push it" into position. The tensioner seemingly only needs soemthing to push/pull against and thus strictly speaking does not absolutely need to be bolted.
4. Re-tap the bolt hole to 10x1.5 fit a suitable bolt and drill out the adjuster to suit.

Much appreciate thoughts/suggestions on the above or anything else I may not have thought of.

Mrmerlin

Get a longer bolt put a nut on it cut the head off
make sure the nut will thread off/onto the cut off part
mix some JB weld put some into the bolt hole put more on the bolt and screw it in use double nuts let it cure

FredR

Hi Stan,

That option I can progress immediately. The bolt I have needs to be threaded some- maybe my tap and die set can finally be used after about 40 years of standby! That or get a new bolt or threaded stud- nothing special there.

If it fails an insert can be fitted but at the moment I have no idea where I can find one over here but they are probably available- that or get an insert kit sent out from either the UK or the States.

Mrmerlin

I would get a longer threaded bolt and cut off the head,
as using a die kit could introduce different size threads to your bolt,
and make the installation weaker.

NOTE the reason for doing the repair this way is because of the location of the area, it makes for a weak standoff ,

NOTE making the internal hole bigger will weaken it and thus it could snap off easier.

NOTE A bolt thats JB welded into the standoff will be much stronger than adding thread cert for this application

FredR

With a new bolt to hand I set about resolving this issue this afternoon. To do that i had to remove the adjuster assembly. As I went to remove the lower bolt I was aghast at what I saw- numb nuts here must have put the 6mm spacer between the adjuster bar and the block instead of packing the position of the adjuster bolt. This effectively shoved the assembly 6mm outboard of where it should be and thus the gap between the top bolt and the block was in effect 12mm instead of 6mm. How on earth I could have done this and not spotted it is beyond me- large brain fart or whatever! I knew when I tightened the top bolt something was not right but even so!!!

I investigated the bolt hole a big further and measured the total depth of hole, [i.e. including 6mm spacer and bracket] to be about 34mm. With a new 32mm bolt that I happened to have in my box of spare bolts I found that I could torque the thing up so will try that. If it subsequently fails I can then resort to the stud bolt approach covered above.

The reason I contemplated tapping a bolt further along the shank was that the bolts in my "bolt box" all came from either my late 90 S4 or the original 93 GTS TBF'd motor so are of known Porsche quality. Getting an 8x1.25 bolt from my local hardware shop was no problem but as I suspected, I would not be entirely sure of the quality albeit they " looked" OK for whatever that may be worth. The biggest problem with cutting threads is when folks use knackered dies. I would have had no problem in that regards my tap and die set is of a good quality make and that particular die has never been used. Use a bit of lube when cutting and turning 1/4 turn max at a time when cutting has served me well previously.

Hopefully no need to do any of this now.

mj1pate

And not to redirect the main topic of the thread, those schrader valves should all be replaced on an extended PM basis. I just did a major AC flush/refresh on mine and replaced all of them.
Since I changed to R134a, I thought about leaving the R134a charging adaptors on my hi/low schrader valves but decided against it. Something constantly pressing against those schrader valves would likely wear them out.
I just wrote the refrigerant change-over history on the top of the radiator so that a later owner wouldn’t be blind-sided

Mrmerlin

NOTE usually you remove the old schrader valves when fitting new 134 ports,
as the new ports have their own schrader valves.
BUT this is an old thread

GregBBRD

In my entire life, I have never done this.
I've never even considered doing this.
(I always put a Timesert in anything with marginal threads.)
It actually is a "good as new" repair and will accept full torque?

Mrmerlin

Greg I would also put a timesert into a blown out set of threads .
BUT, I am talking about the girdle standoffs.
I have replaced a few bolts with pulled threads for the belt anchors into the girdles.
Or the Alt/ PS cassette anchors
The thing is tapping a bigger hole into these specific standoffs weakens them as the internal hole is made bigger,
thus less metal to support the side load.
As you know they are already pretty weak anchor points to begin with.

That said JB welding a stud into a hole might not be the best thing to do but,
I can tell you it does work.

Same goes for JB welding the oil line collars into the girdle after they have been moved and cracked the mounting surface,, that works too.