8 replies to this topic

[Scruffs]

Hi Guys,

Some of you may know I'm dropping a '99 MPi engine/box into an older car...However I'm finding problems with the new engine and want some of your learned opinions on where to go next...I bought it not knowing any history on it and just accepted the risk it could be a duffer, I rather hoped it wouldn't be though!

Dash shows about 45k. Engine was grubby as hell so stripped off all ancillaries and pulled the head to give it a clean and check over.

Immediately suspected a blown head gasket as there was oil seeping from the block-head interface behind the manifolds...also plenty of brown scunge in the header tank which I really should have spotted before...once in the head I found ALL valves and guides need replacing (stem diameters worn), especially the exhausts, and the seats look more pitted than I would have expected...which all surprised me at 45k and got me curious about the rest of the engine

I then took the flywheel cover off to discover a liberal coating of oil all over the clutch. "Oil seal's gone" I thought, which again surprised me at 45k.... so I pulled the flywheel and primary gear to discover that the front primary gear bush has gone and ing twisted!

Now slightly annoyed, I measured the crank axial float - if this was too great then I would have started digging further...however, it's about 60 microns so appears fine...Other than this the only things that makes me believe that this has done 45k not 145k is that there are still the factory honing marks in the bores, the bodywork on the car was pretty good and the compression figures were apparently up at the 15 bar mark

So...any rules of thumb here? If the head's so worn and the primary gear needs a refurb then is there anything else I can expect to be shafted ? Does what I've described tell a nasty tale - such as being run with no oil? Or is this much wear on these bits normal at this mileage for this engine and other bits are probably fine? I guess one of the worrying things for me is that I simply don't understand the loading condition that causes the front primary gear bush to twist like that without it seriously binding up on the crank...

to be honest I don't have a clean enough garage to contemplate an engine rebuild ATM so would likely be on the hunt for another engine and box!!

Thanks!

Al

Attached Files

•  P1010041.JPG   50.48K   19 downloads

[Guess-Works.com]

I would suspect poor service intervals.... and therefore, pull the box off the engine and have a look at the diff wear...

[Scruffs]

Thanks guessworks

Are you talking wear in the pin, the teeth, the thrusts or everything in the diff?

Bugger it.

The very fact I posted this up means I'm pretty much resigned to doing a rebuild/getting another one... I'll be a-visiting your site for a price on a recon box for this I think!

Any other thoughts very welcome

Cheers

al

[Scruffs]

Took off the L/H diff side cover, removed gasket and reassembled finger tight.

Gap is about 250-300u (10 - 12 thou)

Gasket is between 260-290u (10 - 11 thou)

Preload is supposed to be 4 thou/100u right?

So...Something's worn...Measured the gasket with a nice digi micrometer so I'm happy that dimension's OK but I thought they were suposed to be a bit tihnner than that when compressed?

Just about to whip off the rear cover - I'll put up some pictures of that in a bit.

thanks again

Edited by Scruffs, 08 March 2010 - 09:53 PM.

[minidaves]

just normal rover service intervals of 12000 miles, so its only had the possibilty of 3 oil chnages in its life if a person has done it on milage.

dave

[Scruffs]

Just realised tonight the bloody thing was still full of oil! Almost got very messy! The oil's pitch black and there's quite alot of sludge in the sump

Anyway...Some photos of the diff crownwheel and friends...

Crownwheel teeth actually look pretty scored to my untrained eye...Opinions?

Shouldn't there be a thrust washer or something behind than output gear? That clearance is pretty huge but I suppose it thrusts the same way regardless of torque direction...

And it looks like the bearings have been spinning in the housing so I suppose that confirms the preload's come off?

Anyway, looks like I'm into a full engine and box refurb anyway so if anyone can offer any thoughts on the photos I've put up I'll be on my way to numerous other threads!

Cheers for taking a peek

al

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•  Diff1.JPG   39.57K   3 downloads
•  Diff2.JPG   84.17K   7 downloads
•  Diff3.JPG   47.26K   3 downloads
•  Diff4.JPG   59.62K   5 downloads

[Sprocket]

The primary gear may have suffered from heat soak as a result of a slipping clutch.

The scoring in the crownwheel are the machining marks from when it was made, and shows little wear, seen as smooth shiny areas where there should normaly be machining marks. There is little wear on that crown wheel. The marks on the gear casing is just where the bearings are seated, as long as there are no noticable ridges at the edges of the marks there is nothing to be concerned about.

If the crank thrust is excessive, then the thrust bearings are worn. This may or may not go hand in hand with the primary gear bush failure in that, if some one was driving with their foot on the clutch, maybe not depressing it, but just resting their foot on it.

However, looking at the colour of the internals, it looks like Minidaves was correct on the oil changes, which is diabolical.

make sure you at least replace the diff pin with an uprated one, or at the VERY least replace it.

[Scruffs]

Thanks Sprocket much obliged mate...The heating of the primary gear makes sense - essentially losing the interference between the bore and the bush right?

Glad to hear the crownwheel looks good, I'll admit gears aren't my forte to be honest! There are no ridges where the outer brg races sit in the diff housing, just witness marks really. The diff will be rebuilt with an uprated pin for sure, I would like to keep the 2.76 ratio tho so that's probably all I'll do.

Crank endfloat only 60u/2 thou, so if anything it's a bit tight! I'm going to measure it all up properly with some decent feelers now I'm in there

Whilst I'm on the subject of the crank - what's that floss type stuff you wrap around crank journals and then tighten the caps down onto? It flattens it out then you can remove it and measure it to check bearing clearance - I've seen it used but never used it myself or know what it's called...would anyone reccomend it if they can decipher what I'm saying?

Cheers

al

[Cooperman]

The material for measuring the bearing to journal clearance is called 'Plastigauge'.
It sounds as though you need to do a fairly 'light' re-build. If the bores are not excessively worn just hone them and replace the piston rings. The crank may just need a 'micro-polish' which you can do yourself if the Plastigauge check shows correct and within-tolerance bearing clearances on all journals.
The crank end-float is excellent at 0.002", but that tends to show that the car did not suffer clutch abuse. Maybe the primary gear failure is just bad quality from new (not unknown with Rover!).
Anyway, you would be advised to fit a new oil pump, new piston rings (assuming the bores are OK), new cam followers, new timing chain, new bearing shells and thrust bearings plus, of course, a new 'red' seal, new clutch plate, new primary gear bushes.
The advice already given about changing the diff pin, planet wheels and thrust pads is correct. It's easy to do with the gearbox on the bench and will last a fair while if set-up acurately.
A nice and satisfying job, especially when it's all back together and running well again.