'97 Taurus GL 147k: Bolts and Threadlocker

Installed my new stabilizer link this morning (see ball joint thread) and thought my ball joint saga had come to a merciful end, but then much to my shock and dismay I discovered a sheared-off bolt lying on the driveway!!!! Never even heard it hit the ground! Turns out it simply fell out of the backside of the knuckle while I was installing the link! It's one of two bolts that holds the caliper mounting bracket onto the knuckle (I found the 2nd bolt only finger tight and narrowed in the center when I removed it - like it had been stretched). I had previously removed both of these bolts in order to remove the bracket, disc, etc. to free the knuckle when replacing the ball joint. According to Ford, these bolts are M12 x 48mm and they have 10.9 stamped on the head. Ford didn't have any in stock but said they could order them for $20+ per bolt!!! Yeah, right! SOooo, I went looking for my own replacements at just about every hardware store in town (also checked with Autozone and Advance - they had nothing). What I found was while I could come up with a near replacement in terms of size and threading, nobody sold a 10.9 bolt. Alll everybody had were 8.8 bolts.

Now, looking at my Haynes book, the 10.9 and 8.8 refers to the bolt strength. The recommendation is to reinstall either the same strength bolt or a stronger one. I'm wondering if I can use these 8.8 bolts temporarily (say for a week or so) while I locate the 10.9 replacements.

1.) Does anybody know of a good source for these bolts (other than Ford)?
2.) I bought some RED threadlocker for reinstall of the 10.9 bolts when I find them (the originals had threadlocker, but I didn't notice it and failed to put it on the bolts upon reinstall the first time.) Should I put threadlocker on the 8.8 bolts temporarily??
3.) How exactly do you put threadlocker on? Is it a 1/2 band, 1/4 band, all around the circumference of the thread for the full depth of where it's embedded, or just at the end, or what?

These bolts may have already been on their way out (who knows), but I remember as I reinstalled the knuckle that they wouldn't "click" the torque wrench. So I kept loosening them, re-checking the lock on the torque wrench, and re-tightening them - never getting the "click" to happen. I probably overtorqued them causing one to shear and the other to stretch. I also didn't have to tap out the sheared bolt. It unscrewed very easily using vise-grips. So BOTH bolts were very loose even though I KNOW I tightened them (but maybe too much)...

There is a fair amount of difference in the tensile strength of a Grade 10.9 as opposed to an 8.8 (150,000 psi vs. 120,000 psi respectively). Since brakes are a rather critical safety feature of a car, I'd be hesitant to suggest using an 8.8 temporarily.

Honestly, I'd suspect that one or both of the bolts did not get properly tightened during the frustrating ball joint replacement. I suspect that the thin area of the non-broken bolt was due to movement of caliper bracket assembly, causing wear on the bolt. This movement may have been part of the noise you were hearing following the ball joint replacement that you contributed to the loose anti-sway bar end link. With a yield strength of 130,000 psi for a 10.9 bolt, you'd have a really hard time stretching it during the torquing process.

I've rarely used threadlocker when reinstalling these bolts after removing brake rotors and never had one come loose. If you do choose to install threadlocker, one or two drops near the bottom of the bolt (opposite end from the bolt head) should do the trick.

-Rod

I wouldn't use an 8.8 bolt in place of a 10.9 either, now if you came across something higher, I would say go for it. Look on ebay or go to Fastenal for the bolt you are looking for, you will prob find it cheaper at either of those places. If you put everything together correctly, you shouldn't need threadlocker, but putting a couple of drops on the bolt just before you thread on the nut wouldn't hurt anything.

worthirt_99:

I've seen Fastenal around here but never knew what their business line was. Fasteners makes sense. I'll check with them. Thanks.

shorod:

I'm a pretty careful person in most everything I do, but you could be right that they weren't tightened because I know I couldn't get them to "click" on the torque wrench and had to try at least three times (loosening and tightening). It was dark outside by the time I was fighting with this and I was running inside the house to double-check the torque wrench setting and to make sure it was locked in.

SO - maybe this means that the 8.8 WOULD be sufficient for a few days until I get the 10.9's. I think I'm going to have to try it because I need the car and cannot let these two bolts hold it hostage. I'm not driving the car very far, and if I lay off the brakes as much as possible, I'll probably be OK (at least I hope). I'll check the bolts every day to make sure they're not working loose and let you know how it all turns out.

Found the M12x1.75x45mm 10.9's today at an industrial supplier here in town. Had to buy a bag of 10, but they were still less than $6 for all 10! There are some minor differences, however, that I wanted to run by you guys:

1.) They're called "black" bolts, not zinc or yellow zinc. Does that matter? They're still stamped with the correct hardness. The originals are a dull silver/grey - which I'm guessing is zinc.

2.) The hex head does not have what I'll call an "integrated washer". The originals have the hex head which molds into a washer-like collar, then the stud begins. With these new bolts, there's the flat hex head, then the stud starts immediately underneath. If I add a washer, it'll be almost exactly like the original. Is there such a thing as a hardened washer, or can I just use the washers I purchased with the 8.8's?

the dull silver/gray is usually a galvanized bolt. The washers you have for the 8.8 bolts will work, they are washers. If they are zink coated and the nuts are galvaized or zink, just watch for corrosion which will weaken the bolt. That starts to happen when you mix metals or coatings. Otherwise you will be fine.

If you want to get them, there are hardened washers out there, but they are a little bit harder to find.

Installed the 10.9 bolts this weekend - along with the hardened (black) washers I got from the same supplier. Used two drops of the red threadlocker on each bolt and torqued them down to 80 ft lbs (I think it was). I feel pretty good about this now. I DID end up using the 8.8 bolts for the entire week, driving very gingerly, not coming to any hard stops. Theses bolts came out looking pretty good, I thought. No signs of stretching or pitting, but maybe the naked eye can't see whatever damage might be present.

Closing the book on the ball joint job. Thanks for your input shorod and wirthirt_99!

Thanks for the follow-up, glad to hear things are going your way again!

-Rod