Tom. M

Hi all,
I have been having issues with bolts on my engine backing out over time and causing other issues.

First it was with my AC compressor, those kept coming out and finally fragged the system, so I took it out. The other times, the bolts on tensioner would back out and then get sheared off by hard engine braking or kick starting the motor while rolling putting undue strain on the belt/tensioner. This time I put some blue loctite (for vibration issues) on the tensioner bolts (the two that are left holding it in right now), but in reading PorKens tensioner pdf he mentions that only anti-seize is to be used on bolts in aluminum and loctite for those going into steel. I am going to switch to his tensioner system as soon as he has another set of brackets.

So the big question is, what is causing these bolts to back out (and only on the passenger side of the engine. I have absolutely no issues with either the power steering or the alt? I do have a very buzzy motor at high revs...as I can feel it through the shifter. Is this a GT phenomenon ...or something else? Has anyone else experienced bolts backing out on their engine?

thanks in advance,
Tom
89GT

SwayBar

Have all those bolts been torqued to spec with a calibrated/verified torque wrench?

Tom. M

This has been happening since I have owned the car. Dyno'd at 283 totally stock when I got it..now (about 2 years ago actually..but in same general config) put down 299 at the wheels. I am still running the 24lb injectors that I put in when I had the turbo on the car. I am also running a bypass on the ignition monitoring circuit due to issues with the 30lb inj I had in there at one point with the turbo system. Haven't returned it to stock just yet. Waiting to get a custom sharktuner chip set mapped for the 24's I have in there currently.

As far as torqued to spec...no but I guarantee I'm tighter than spec. One note, after the last failure I have run for a year or so without issue and even on long trips etc. After recently doing a tbelt/waterpump I checked the tensioner bolts and they were fine. I suspect the running at "high" speed trip over to Spokane is what likely caused the bolts to back out and the hard engine braking is what forced the bolts remaining to snap ...

My only fear with going with the Porkensioner is that the tbelt warning circuit is by passed. Both times my tensioner failed...the system warned me and saved my engine. With out those warnings, the bolts on the porkensioner bracket will back out until the whole thing just falls out...and all my valves go buh by...

So...what are the torque specs for the tensioner bolts? Can I use loctite on them?..
Later,
Tom
89GT
P.S. good idea on the exhaust temp check..I've got a laser temp gauge on the way...I'll check them out...to see if there is a temp differential between cylinders.

Mike Simard

It's possible that your bolts could have been overtightned at one point in their life. They could have yielded and not be capable of holding torque anymore.
In general the force on the threads of a tightened bolt will keep it from loosening, Loctite may be good practice but shouldn't be the plan, if a bolt is tempted to come loose there's another problem. It would be good practice to discard any bolt that came loose.

Edit, we typed our posts at the same time. You just said " I guarantee I'm tighter than spec".
Ah Ha! That sounds like a problem.

69gaugeman

You can use locktite on anything! but I would be wary. The blue 'removable' locktite would be the one to use. As said above there has to be a reason. If it is excessive vibration and you want to live with it lock washers would work fine as well. They make them for allen head bolts as well

Tom. M

There are all new bolts in there....as the old ones were either sheared off...or mysteriously backed out and are lying on the side of I90 on the way to Spokane.. Either way..I will get that last one drilled out so I can get 4 bolts back in there and then tighten to spec (with a proper torque wrench). In all likelihood I will be converting to the porkensioner..but will religiously be checking those bolts. I will look into the upper rev buzziness too as I believe that also plays a part in the bolts coming out.

thanks,
Tom
89GT

Garth S

What shape are the motor mounts in? ..... re transmitted vibration ... which can back bolts out ..

PorKen

Don't GTs pit their cams because of the undamped rebound of the cam as it comes off the hi-lift lobes? Putting in a proper hydraulic tensioner/damper may reduce the (lumpy) cam related vibration?

You could put the PKsn'r belt-light-bypass ground wire under one of the suspect bolts.

Tom. M

Yah know...I just thought of that too...I suppose it should go on the one that leaves the block first..

and for the record..my GT cams have no pitting

Later,
Tom
89GT

BC

I have not heard of this. I use never-sieze on steel and Al.

I use the purple loctite on bolts like for the waterpump and the tensioner. even weaker than blue, but they actually come out when I need them to, so...

PorKen

I read there was a danger of pulling the threads with Locktite in aluminum, so I put that in the manual.

Tom. M

I used the blue on the two holding the tensioner right now..I guess I'll let you know how they come out when Ken sends me a Porkensioner ..

later,
Tom
89GT

marton

wierd,
nobody else posted they have similar problems? Would be interesting to hear & compare.
Maybe it is just some unwanted feature of your 928... I can only assume some PO damaged the threads somehow?

Marton

Tom. M

Well...lets not get too deep into the PO mechanics incompetence..but the tensioner was not properly rebuilt...had two broken bellville washers and no oil to speak of and was way overtensioned...that is what led to my beer run valve crash episode a few years back at the Track Attack. Got that taken car of and rebuilt the tensioner....but didn't realize that they also forgot the circlip on the back of the roller the tensioner pushes on...so the tbelt warning came on due to poor tracking of the belt. When i figured that out...everything was good >....or so I thought......I'll be digging deeper into the vibration issue soon .....

BTW..I did see a post about A/C bolts backing out a month or so ago...so there are some out there with similar issues..

later,
Tom
89GT

JP Rodkey

I'm pretty sure the rare times I've ever encountered loose bolts was because I didn't remember to tighten them properly when installed. On the other hand, it's easy to see how an A/C bolt would be a good candidate for backing itself out because of resonant frequences amplified by the mass of the clutch assembly.