The dreaded crank endfloat issue.
Turbo Mini Forums

Guys,

I started my car for the first time about a month ago, sorted some running problems etc and now it starts perfectly.

I started the car for the first time today since wiring up my rev counter. Unfortunately the rev's dropped from about 1200 to sub 500rpm when the clutch is pressed down - not ideal!!

Nic was round mine at the time and agrees that something is amiss, but I just wanted to check with you guys that the engine definately needs to come out?

There was a thread where a few people were talking about this happening to them but cant find it. I know some people said that this occured on their fresh builds using uprated diagphrams (mines a single grey), and that everything turned out ok after a bit of use?

But I think a 500rpm+ (to almost stalling) dip in revs is too severe?

What do you think?

Edited by richminiturbo. on 11th Jun, 2009.

time to dismantle and inspect!

My first engine did this when I rebuilt with a grey cover and I hadn't had the thrust faces on the crank machine. It eventually made the engine stall when the clutch was pressed in!

if youv'e leaft the engine for a period it is possible that the diaphram has stuck or partially stuck/seized where it sits on the flywheel, if it is not free to rotate most of the clutch pedal effort is simply pushing the crank onto the thrusts,

slacken off the three cover bolts and put a little oil around the joint mentioned above, re tighten and give pedal a dozen+ depressions to try work some lube in to area.

Edited by fastcarl on 11th Jun, 2009.

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Don't rip it down just yet, my engine did this, but has got better as everything bedded in.

^^^^^ (as fastcarl stated) thats what happened with me but I had to replace the crank,flywheel and diaphram, hopefully your wont be as bad

Edited by Tweaked on 11th Jun, 2009.

Thanks for the the advice guys.

Carl- I will try that and see how it goes, thanks alot! It's been sat for 6 months and is a fresh build so i'm hoping it's that.

Tom - Can you recall how much your revs dropped? I'd definately try and drive it and give it the oppurtunity to bed in, but would rather not damage the crankface and components in the process if you know what I mean!

Tweaked - How come you had to replace the fly and diagphram aswell?


Also, would I get an accurate reading of the crank endfloat by removing the starter and getting a DTI on the fly, then levering the crank back and forth via the crank pulley?

Cheers

Hi,
That should give you a good idea of end float, tricky to use a mag DTI base in that area though!
Cheers,
Gavin :)

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I'm sure it was a lot at first, and I thought it was catatrophic. If you checked the endfloat when you built it and that was right then it will just need to settle down.

The locking washer that holds the flywheel came loose eventually and caused the flywheel to spin on the crank, shredding it to bits. Replaced the diagphram because it was abit rusted and was not releasing properly, so when I pressed the clutch everything (crank, flywheel etc) would be shoved causing the engine to drop in revs eventually stalling it. O and bent quite a few clutch arms while sorting out the problem.


[quote=richminiturbo.,11th Jun, 2009]
Tweaked - How come you had to replace the fly and diagphram aswell?/quote]

Cheers for the replys!

Thats the thing Tom, I had quite an issue when originally building the block.

When building it for the first time (my first ever build), I got to the point where you fit the thrusts, one side went in fine but the other did not fit. From what I remember both of these were standard size thrusts. So I took it to my local engine builders who machined abit of one of the crankfaces to make them fit.

When I asked, they said there was a very minimal amount of endfloat and thats what I needed, as it would "bed in" when first run apparently, I didnt have a DTI to measure the endfloat, but was assured that I wouldnt "feel" 3thou of endfloat by hand, it did feel like there was no give though. So I carried on and built up the rest of the block/engine up, while reading of a few people getting the rev-drop issues on new builds and finding buggered thrusts upon strip down.

Now that i've built it up ive been really paranoid about it, alas its happening so i'm just going to take it apart and make sure.

I had the pressure plate off earlier and gave it a bit of a lube but that didnt help the issue.

The engine is now disconnected and on breeze blocks ready to be lifted out and stripped hopefully this weekend.

Should I expext to see shagged thrust washers? I've put my foot on the clutch with the engine running only 5 or 6 times in total so perhaps i might get away with it?

Why didn't you have the trusts machined instead of the crank? Much easier...

It was back at the start of 07' when I was building the short motor so it was all new to me, but I guess the engine machinists should have thought of that one!!

Engine is still waiting to come out, not sure when i'll get the chance to take it out but when I do i'll post up my findings.

Schrödinger's cat - so which one am I ???

Right! Finally got round to getting the engine out and in pieces.

Whipped the thrusts out and checked them over. Here's the condish they're in:





As you can see, the thrusts do look a little worn in parts, the rights in particular (both from the flwheel side!). They're STD sized thrusts (2.2mm thick).

You can also see that the centre main bearing has worn at the bottom, is this a problem? What would cause this??

Do the thrusts and main bearing look re-useable?

The crank faces were ground Rod yes, and they still look pristine which is a bonus. I checked the primary gear ring when taking it off, and the chamfer was the correct way round.

The only other thing that was weird, was the flywheel bolt wasnt very tight at all, i'd forgotten to put some threadlock on it when building but torqued it up correctly, would this have caused any issues? However the flywheel was home on the crank sufficiently.

I'll be checking the endfloat asap, can this be done with the crank pulley and gubins still in situ?

Cheers

Edited by richminiturbo. on 28th Jun, 2009.

nothing that unusual about the thrusts,or the bearing for that matter, they look perfectly reusable to me,



carl

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if you put them back i would swap them side to side, so the ones that are unmarked are where the marked ones are now

As per Carl, seen a lot worse running fine....

Yes, you can check the endfloat with all the pulley, timing gear still in place, just make sure you re-assemble the centre main bearing/thrusts as they would normally be and have the DTI mounted on something secure and solid when you push the crank backwards and forwards. You will also have to push/lever a bit harder with all the other bits still in place.

Schrödinger's cat - so which one am I ???

Brilliant! Thanks guys.

What endfloat would you recommend? I did read somewhere on the forum before that for higher performance engines its better to start with a smaller endfloat?

3 though seems to come to mind? If I need to make the thrusts thinner to achieve the right endfloat, should I just get one side on some wet and dry paper (what grade?), or do all 4 in small amounts?

I'm hoping its too little endfloat thats caused this whole thing in the first place. I'm glad the thrusts are ok, I only really dipped the clutch a handfull of times before pulling it :)

i've used 800-1000 grit wet and dry before, and some wd40.

I always do tham a bit anyway to level out the part no stamp on the back, then check the clearance.

keep measuring them as you go as you can end up with them tapered.

oh and 2- 3 thou is what i aim for for road stuf, for a real rever i'd open it up to 3-4-5 thou.

Nice one cheers joe!!

I'll aim for about 3 then and see how it goes..

It must have some end float already otherwise it would bind really badly, would lets say 2 thou more endfloat make THAT much of a difference? i.e stop the revs dropping by about 1k?

It all depends on how much you have now doesnt it. If you dont have enough, then the extra thouage might stop it binding.

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well, TBH hinking about it i think the endfloat is probably fine as the thrusts are only marked on the clutch side, if it was too tight there would be some marking the otherside too...

any chance of theom pics of the crank?

... nice plectrum...

That lloks good, but CHECK carefully the endfloat even if you reuse the thrusts. This is because you wear off the "high spots" effectivly increasing the endfloat the first three minutes.
This is why 2nd hand thrusts are great.