Hi.
I'm replacing the harmonic balancer on my 1989 v6 and since the car is 50 miles away from where I live I'm trying to get all the tools together to fix it in one try. So does anybody know by chance what diameter and thread the center bolt of the crank is?(I want to make the installer tool out of a bolt with the correct size). Thanks.

 

Glad to hear you're not using the center bolt to pull the balancer on! (I just wrote about that, and how my center bolt snapped off, flush with the crank snout.)

Unfortunately I can't remember what size that damn bolt was... grade 10.9 is all I can offer. I -think- the thread pitch was 1.50? Possibly an M12? Dammit. Sorry!

 

Never mind. I read your article and therefore I m not using the center bolt. But if it's somewhere around M12/1,5 I can take some normal hardware stuff. I replaced the AC hub bearing on an LT 1 once they used some fancy thread I think it was M22/1,5 now that was hard to get. Thanks TomP
I think my girlfriends Neon had M12 too.

 

I need to buy myself one of those bolt thread/size gauges one of these years... would make my life a whole lot easier. To replace my exhaust manifold bolts I had to bring an old bolt into Pep Boys, to match up against their hardware aisle's bolt trays.

 

I got one from my girlfriend. Really useful that stuff.

 

what girlfriends or thread guages?

 

Girlfriends that give you thread gages as a gift of course.

 

Bernd, when you find out what size it is, please post it!! Thanks!

 

Sure I will do so. I get to it probably next friday.

 

Okay I got it more or less.The centerbolt of the crank on my engine has the following specifications: Bolt head: 18mm strenght: 9.8 dimensions: M12*65 with 35mm of thread. Since I forgot to take along my thread gage I could not identify the thread pitch but I m sure it has to be numericaly smaller than 1.5 (I tried that one). my guess is that it's 1.25 or maybe 1.0 I will check on that at a later time. What I did however to get the harmonic balancer on again was to use the original bolt. It did work without braking anything. What helped me maybe was that I used some extra thick washers between the bolt and the balancer. I can only assume that in order to brake the bolt you have to thread it all the way in the crank, buttom out in the threaded hole of the crank and there it goes. But that s just guessing. It was not all too hard to get the balancer on strenghtwise. Unfortunately the shaking did not go away. Maybe it was a little bit better than before. Must be a vacuum leak I hope/pray.

 

Are you sure the strength isn't 10.9? Thanks for the other specs!

Oh and glad to hear the bolt didn't snap on you. When mine snapped, it wasn't even close to bottomming out. It pulled the balancer on maybe 1/8th inch.

 

I'm absolutely sure about the specs of mine. But I m not sure if it s the original one or not.It s quite interesting to look at the rubber of the harmonic balancer it s as the saying goes solid like a rock there is nothing rubber about it anymore. The outer ring did move so that it wobbled but it did not move clockwise or counterclockwise which kept the timing right. Strange that rubber on a "new" car (1989) deteriorates so much and on my fathers CJ 7 Jeep which is 1981 there is nothing wrong with it. Probably poor quality?

 

I talked to the guys at my local bolt and nut store about high strength bolts. They told me that if something happens in the manufacturing process like using the wrong rust protection these bolts (numerically larger than 8.8) become very brittle in fact they can even break when you drop them on the floor. That is why they offer these bolts only with a black finish and not with the usual zinc cover on it (the hydrogen is the problem I believe). Otherwise it is rather unlikely to break a 10.9 with standard tools. Maybe that was the problem.