fixing a potentially threaded set of holes

[Thirteen13]

Howdy,

Ive done some googling and searching, but i cant find what im after.

Im in the process of chucking my coilovers in and when replacing all the bolts and putting it back together, 3 holes for the rear suspension arms seem to not allow any of the bolts to go in.

Whenever i get a bolt started on the thread it will go in perhaps half a turn, if you move it by finger its just stuck. If using a socket, you need ALOT of force to make it turn, which has that "cross threaded", metal biying in feeling. The 3 holes all are doing it.
Looking at the tips of each of the bolts the threads are not nice clean cut, but rather shiny flat threads that are silvery and smoothed over. So i think each of the holes are destroying the bolts.

The suspension is all in ready to go, but the car is undrivable without the rear suspension arms bolted in.

Ive never encounted this before, but it has to be fixed to make the car drivable again! Hell i want to test out my new coilovers too!!

Suggestions? Should i use a tap to try to clean up the inital threads ?
Thanks

[Hen]

That sounds like a classic case of right size bolt but wrong thread pitch (and Toyotas use different thread pitches from most non-automotive hardware). Are you 100% sure you're using the same bolts you pulled out of the holes?

Check the condition of the threads in the hole, try measuring the pitch in the hole if you can (can use a smaller diameter bolt of known pitch and see if it sits "nicely" in the threads), measure pitch of bolts.

You could clean the threads up with the correct tap, or even helicoil it if required, but hopefully you won't have to resort to this.
Hen

[Thirteen13]

Bit of an update, 2 holes just needed a little persuasion and i got 2 bolts tightened home fully. So 2/3 are in. Lots of wd40 and cleanign up the threads.

Problem with the last hole, if u attempt to tighten it just starts to squash down the threads.

[Thirteen13]

Hen, i couldnt honestly say for sure, but judging from these particular bolts, all 3 are used to hold the rear suspension arm up, so i could only assume they are all the same size and thread pitch. All 17mm. Basically the 3 bolts are undone, to move the arm around so the coilovers can be dropped out of the mounting point. Once the coilover is bolted in, jack the arm back up into place, as it moves snug back into its spot, with the hole aligned, then put 3 bolts in and tighten.

[Supra967]

new bolts or old? If new and still have old, get one of each, sit threads inside each other and hold up to the sun. If they don't mesh exactly they're the wrong thread. Otherwise just get a tap and run it through, don't wreck the thread any further.

[Thirteen13]

Just re-used the original bolts. I think its only the first 1-2 threads in the hole which is causing the problem, so i definately think the hole has more than 90% of the original threads left, so ill run a tap and hopefully save it.

[Thirteen13]

problems fixed. the hole was fine, but the bolt was leaving some burrs behind in the hole, Ran a 12x1.25mm tap thru the hole, removed the junk, bolt went straight in.
Hoo ray!