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F20C2 Thrust Washers and Excessive Crankshaft End-Float

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F20C2 Thrust Washers and Excessive Crankshaft End-Float

Old 09-21-2018, 02:01 AM
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Default F20C2 Thrust Washers and Excessive Crankshaft End-Float

Following an earlier post (quite a while ago, in fact) I thought I’d provide an update and outline what I learned in the hope it may help someone else. First, here is a link to the previous saga:


In fact, the situation was slightly worse than I first thought. I was measuring the end-float by setting up the dial gauge with the crank pulley pulled fully forward, walking round and pressing the clutch, then walking back and reading the difference. As I now know there can be a degree of over-swing on the end-float measurement which I only discovered when I videoed the dial gauge, so the final measurement for my engine was 0.52mm with an overswing to 0.65mm. Lesson one, either video the gauge or get someone to push the clutch for you as you watch.

So, armed with this information I sought various opinions on the best way to fix it. Obviously new thrust washers, but engine in the car or engine out? And this is where things go a bit awry, plenty of people have suggestions, few have knowledge and even then one name I thought I should trust measured the end-float and came up with a different (lower) value to mine that was just in spec. Lesson two, it’s not difficult to measure the end-float accurately and I should have insisted he remeasure using my method. (To explain, as I found out later he mounted the dial gauge magnetic mount on the front cross member in front of the crank pulley with the plunger on the crank bolt. Because the engine mounts can move, this movement negated some of the end-float and hence gave too low a reading. To get an accurate value the dial gauge must mount on the engine with the best possible geometry.)

Having measured again myself and convinced myself I was right, I then started asking about the best fix. Nearly everyone said engine out. Most said impossible with engine in. Some said maybe with engine in, but better with engine out. Tom Gannon at TGM said engine in, need to be careful, but it’s possible. I looked at the maintenance manual and I could see how it could be done, although I wouldn't attempt it myself. Lesson three, after talking to everyone do your own research and trust your gut instinct about what seems possible and what's not.

So that’s the route I took, and here’s what came out:

The engine had 21120 miles at the point the thrust washers were changed. Tom changed them by dropping the lower cradle with the engine in the car, and didn't even remove the timing cover! (So, all naysayers please note, it is possible to do the job in situ.) The total bill was for five hours labour, an oil change and a new set of thrust washers. Excellent service from TGM, I would definitely recommend them for S2000 mechanical work. Tom is a top chap.

As you look at the picture, the washer on the left is the "front" washer, the one that carries all the thrust loads when the clutch is pressed, the one on the right is the "rear" washer which as you can see only has minor wear. There have been anecdotal reports of washers in 2009 engines installed back to front, these were in the correct orientation but mightily worn. Also, even despite the original mammoth end-float value of 0.65mm the crank hadn't touched the block (phew!) but didn't get away scott free either. There is minor wear to the thrust face that opposes the most worn washer, quite smooth if you run your finger over it but not the polished face you would expect. If you examine the thrust washer the lead-indium bi-metal has completely worn though to expose the steel backing. After discussing with Tom we thought the best plan is to try new washers and see how they fare. If I'm lucky the end-float will stay in tolerance, if I'm unlucky the worn crank face will ultimately cause accelerated wear on the new thrust washers and I'm looking at a new crankshaft in due course.

So, the final result? After 170 miles of driving I'm back to an end-float measurement of 0.28mm. My plan is to measure the end-float every 1000 miles or so, if it stays steady then happy-days and the fix has worked, if it starts to grow (the service limit is 0.45mm) then it will be engine out and new crankshaft, bearings etc. So fingers crossed.

If anyone wants further info or meets a similar situation please let me know as I have gained a lot of knowledge I wish I'd had a while ago. How does the saying go? "Experience is what you now have just after you needed it."

Last edited by ValveBounce; 09-24-2018 at 02:19 PM.
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Old 09-21-2018, 02:47 AM
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Thanks for posting
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Old 09-21-2018, 03:44 AM
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Nice work definitely one of the better threads, well done, hope you have dodged the bullet...
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Old 09-21-2018, 06:26 AM
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Originally Posted by tozerman View Post
Nice work definitely one of the better threads, well done, hope you have dodged the bullet...
Thank you, I hope so too!

It might ultimately cost me a new crankshaft and associated bearings etc, only time will tell as I periodically check the end-float, but at least the whole engine hasn't been trashed and I now know what's going on inside.
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Old 09-21-2018, 07:59 AM
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Good write up, fingers crossed for you
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Old 09-21-2018, 12:28 PM
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Interesting read, good luck with the fix.
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Old 09-21-2018, 11:18 PM
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Old 09-22-2018, 04:11 AM
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Really useful info there, VB!

Interesting that they're not reversed (did seem a bit too much of a schoolboy error) but looks like a batch with a manufacturing defect.

It'd be interesting to see how the crank face fares. I think I'd stick to your schedule of five-hour oil changes, as removing the crank to re-polish it is too much like hard work until it's urgent.
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Old 09-22-2018, 11:13 PM
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Excellent news fingers crossed on the crank surface also good to know for other owners of said years that if caught early enough there is a fix without great expense,

Well done for having the forethought to check the end float and potentially save a bad ending for a low mileage engine
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Old 09-24-2018, 12:24 PM
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Thinking about this when we were rebuilding my sons F20c we found that at 80k miles the thrust bearings were still well within service limits as quoted in the Workshop manual, in fact the bearings had very little obvious wear.

We stuck a new set of bearings in, and and the measurement,s we took showed the float to be back inside the factory new tolerances, let alone service limits. in fact we found virtually no wear on the crank journals both in absolute diameters and ovalitly.

we measured the float with the obvious benefit of of having the engine upside down and full access, can’t remeber exactly what we were able to use on the crank and block as measure points but it was consistent and were able to take two measurements with a mic to get the float.

Now if the crank faces are worn , scored or both can they not be refaced , possibly built up again to the OEM limits for new OEM bearings or possibly finished under OEM size and new over size bearing purchased or made ? Some one some where must be able to do this ? An engine builders and machinist can surely build up the surfaces ( for the life of me can’t remeber the name of the process , similar to spark erosion in reverse ) then machine back to correct dims for OEM bearings?

If as as you say the crank bearing surfaces are good why would you suspect the current bearings and the measurements taken will rapidly wear to a point in excess of service limits again ? did you or they measure the distance between the bearing surfaces on the crank ? Was this dimension as it should be ? The other thought is did Honda have a duff batch of underside bearings which caused the problem in the first instance ? As I recall the tolerances for this are quite course and not particularly tight.

The other thought i keep having is around the longitudinal loads imposed on the crank by the clutch etc does this have something to do with the accelerated wear ? Was something shoving the crank hard one way, did the bearings have one showing significant wear and one not ? This would support my theory and explain the rapidly increasing crank float.

Not really looked but there must be some where to locate a DTI stand or mag base on the block , or even bolt or clamp on a bit of steel plate for it to stick on to allow accurate measurements to be achieved engine in.

Just by way of an update Toby has his engine back in after pulling it down again and balancing every thing , crank was spot on in fact out of the factory. After market bit were not that good , the clutch assembly being very poor. Spoke this evening he just has fill it with oil and a few minor other bits and bobs before starting it with his original engine map. Then 30mins or so with varying rpm , then new oil and filter and drive 500miles , oils and filter another 500miles then Dyno. About time he’s been twiddling around with it for ages and despite the care he has invested he’s still not convinced it’s going to be ok. Stick on big turbo and Dyno for lots of BHP,,,,!!!! Why ?
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