TR6 Corrected post regarding knocking TR6/Clutch issue

[Brosky]

I deleted the previous post because I had the facts stated incorrectly and only had one reply for help. So here it is, as it should have been.

My friend recently purchased a frame off resto and was driving it one evening, when he down shifted from 3rd to 2nd gear and suddenly heard a loud knocking noise. This noise is throttle sensitive and only occurs when the clutch is depressed. Revving the engine increases the noise, but it remains at an idle with the clutch engaged. By this I mean that it seems to hit more frequently when revved as apposed to simply getting louder.

The engine was rebuilt and the crankshaft was cut and fit with the correct bearings at that time. We're beginning to suspect the thrust bearings.

I'll be going over after work to look at the fan/pulley movement when the clutch is engaged and will take my car to compare.

Any thoughts?

 

[michalotti_tr]

Re: Corrected post regarding knocking TR6/Clutch i

I would agree - it sounds like a thrust washer issue. I hope y'all have caught it in time!

I'm just starting the tear down of my TR6 engine, and one of the modifications I have planned is to cut the bearing cap and use two thrust washers, preferably those special bronze ones offered by Scott Helms.

As an interesting side note, being a new owner of a Miata I discoverd that they use the same exact design for the thrust washers in their engine and that they also had an issue with them falling out and destoying the engine - deja vu anyone?

 

[martx-5]

Re: Corrected post regarding knocking TR6/Clutch i

Actually, the Miata #4 thrust bearing issue only occured in the '99 & some '00 and was the result of a mis-machined block and bearing cap. They took off too much material, and when they used standard sized thrust bearings, they got beat up and eventually failed. /ubbthreads/images/graemlins/hammer.gif Mazda replaced a lot of engines, and some that were past warranty. And, yes they did make noises such as you're experiencing.

And I agree, this sounds like a thrust bearing issue. You should be able to see easy enough.

 

[Brosky]

Re: Corrected post regarding knocking TR6/Clutch i

It appears to be the thrust bearings. John and I ran the car and upon the engagement of the clutch, the fan and pulley definitely move forward a noticeable amount. Rather than risk any further damage, John decided to pull it down tomorrow night. Naturally, it will be over 100 by then, but that's when these things happen. Or it will happen when it's 15 degrees above zero.

All in all, as long as there is no damage, the oil pan gasket needed replaced and he does have a very small exhaust leak at the flange, so he would have had to pull the pan anyhow.

It's amazing how easily I can justify someone else's work, isn't it?

 

[Brosky]

Re: Corrected post regarding knocking TR6/Clutch i

John did pull the pan and found that the thrust washer was falling out. Perfect timing, before a major failure or during a long trip.

Parts are on order and should be back up and at it by Friday.