Spun bearing on 990

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tinmantom
Posts: 3
Joined: Sun Apr 14, 2019 11:52 pm
Location: Derby

Spun bearing on 990

Post by tinmantom » Tue Apr 16, 2019 10:21 pm

Hi,

I have a 990 which started to drink oil, developed a knock and was giving out white smoke. I dropped the oil sump and found some swarf and a nut (!) which was a bit of a shock.

The nut was from cylinder 1's big end bearing - I took the other one off and found the bearing had spun and either disappeared or welded itself to the conrod. I also noticed oil seemed to be seeping a bit from the head gasket so thought it was time to dive in, clean everything up and get the head off.

No obvious cracks to the head and checking it with a steel rule and feeler gauges I can't find a warp. I did however find a couple of the water-ways were clogged up with rusty deposits and one had a fairly sizable bit of liquid-gasket which I tweezered out - the water pump has a fairly messy liquid gasket which I haven't removed yet but I assume I will for the rebuild.

I guess that the head is not originally from the same engine as the block - there is a waterway in the head that I don't think has a corresponding way in the block (although it had produced a bit of a rusty bump which I've gently scraped back down to level) - when the new gasket arrives I hope it will just have the holes for the block... The second discrepancy is the air manifold ports have three bolts on the head but only two on the manifold so the extra ones have been cut off. A fairly rough job was done though so some of them are up to 2mm proud - obviously taken up by the gasket previously but wondering whether folk think I should do a better job of making them level. Block serial number is Mc25389, head is F921438.

I guess I'd be keen to hear peoples thoughts on how precious I should be about trying to get the crankshaft and big end journals smooth before I reassemble (with new bearing shells) and see if things are in better shape. I've got the journals fairly smooth but there are still some grooves. And I'm yet to get to work on the crank but have been watching various videos involving shoelaces and honing paste!

Apologise if any of the terms aren't right here - it's been a steep learning curve this week! I did rebuild my car engine when the timing belt snapped but I had a haynes manual for that - this time all I've got is the head torquing pattern in the maintenance book so I feel like I'm winging it a bit - any do's and don'ts would be greatly appreciated!

Cheers

Tom

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db2d
Posts: 2024
Joined: Fri Feb 24, 2012 10:01 pm
Location: Monmouthshire

Re: Spun bearing on 990

Post by db2d » Tue Apr 16, 2019 10:51 pm

Can you supply the engine number please so that the engine type can be identified

tinmantom
Posts: 3
Joined: Sun Apr 14, 2019 11:52 pm
Location: Derby

Re: Spun bearing on 990

Post by tinmantom » Tue Apr 16, 2019 11:18 pm

Excuse my ignorance where do I find that? - the block has E W 2 , 2 A O and Mc25389 cast into it. Then the printed label has 10279 written on it.

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db2d
Posts: 2024
Joined: Fri Feb 24, 2012 10:01 pm
Location: Monmouthshire

Re: Spun bearing on 990

Post by db2d » Wed Apr 17, 2019 6:47 am

Stamped in the cylinder block on the lower front corner below the dynamo.
The numbers you have supplied are casting numbers.

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cobbadog
Posts: 466
Joined: Tue Oct 11, 2011 6:18 am
Location: beautiful Coopernook NSW. near Taree. NSW. Australia

Re: Spun bearing on 990

Post by cobbadog » Wed Apr 17, 2019 6:58 am

If this is your tractor and you are going to put it back towork don't mess around have your crankshaft machined properly. You will thank yourself for that later on in years of reliable use. Once machined you will then know what size bearings you need to buy.
Simply cleaning up the journals is not the best way to get a good result even it is jsut to rum around the parade ground at Rallies. I have never regretted doing my engine up properly and after almost 4 years of running the tractor at Shows and on treks it is comforting to know that it is a reliable tractor and not waiting for the same bearing to spin again due to an improper repair.

philedge
Posts: 207
Joined: Sun Dec 03, 2006 11:27 am
Location: Chester UK

Re: Spun bearing on 990

Post by philedge » Wed Apr 17, 2019 9:12 am

Where you go from here depends on how deep your pockets are, how much time you have and how important the tractor is to you.
For what you could spend on an engine rebuild you can probably buy a running tractor.

If the journal is scored but smooth you may get away with a polish and new shells. If your on a budget or can afford for the tractor to be out of service in the future clean up the journals as best you can an put some new shells in. See how the oil pressure is once the tractor is running again. Id give the con rod a good inspection if its been run with the cap loose and if youve got the head off maybe put a replacement rod in. If you want to spend money and/or the tractor is important to you then spend the money on a rebuild.

Bear in mind that if one journal is scored its likely through neglect and other parts of the engine may be worn too.
'66 880 Selectamatic rat.

tinmantom
Posts: 3
Joined: Sun Apr 14, 2019 11:52 pm
Location: Derby

Re: Spun bearing on 990

Post by tinmantom » Wed Apr 17, 2019 12:35 pm

From behind the lift pump I see K956168F - if this isn't it do I need to take the dynamo off to see it?

Thanks for everyone's input so far. We use it for an intense few days once a year to do a hay cut on 30 acres - the rest of the year it is infrequently used to move trailers of logs down to the house, occasionally grade the lane and drive a log splitter off the pto. I wonder whether the splitter might be the cause of this - it's a new addition and I've been reading that running such things isn't a nice regime for the engines.

I assume that getting the crank out for machining means bringing the whole block out? What would be a reasonable price for machining the crank in the UK?

Pockets aren't super deep, time is indeed very short (not least because without a barn everything feels very vulnerable opened up as it is) and although the tractor is important it's mainly important as a working machine which - as Philedge points out - we could well get a replacement either as a donor engine or a whole new tractor.

By inspecting the con rod do you mean for cracks?

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ollek
Posts: 3668
Joined: Tue Apr 10, 2012 1:20 pm
Location: South West Finland

Re: Spun bearing on 990

Post by ollek » Wed Apr 17, 2019 12:58 pm

The number K956168F is a casting number, not the engine serial number. As said, the engine number is stamped on a small flat surface below the alternator, not behind the lift pump, and the number can be painted over. The number should start with AD4 for the engine type and then go on with numbers only.

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bedwards1966
Posts: 845
Joined: Sun Mar 07, 2010 10:36 pm
Location: North Yorkshire

Re: Spun bearing on 990

Post by bedwards1966 » Wed Apr 17, 2019 10:19 pm

Obviously your crank is not very healthy. If you can see rings round any of the journals it should be reground to make things right.

However, for an engine that's only doing fairly easy work on a small scale you can sometimes get away with spending some time with strips of very fine emery to polish it up and make it all smooth, provided there's no deep damage. If you can catch a fingernail on any of the marks, get it ground. If you want to know that it's all done properly, get it ground.

When you have the head off you will probably find that it would benefit from some attention to the valves, generally head work isn't expensive.

philedge
Posts: 207
Joined: Sun Dec 03, 2006 11:27 am
Location: Chester UK

Re: Spun bearing on 990

Post by philedge » Wed Apr 17, 2019 10:26 pm

For the con rod, if the engine has been running for even a short time with only one bolt in place and one or both shells missing check for cracks, distortion or bruising where the shells sit.

To get the crankshaft out for repair Im pretty sure youll need to split the tractor to get the flywheel off so you can remove the crank.

If you want an engine service manual, search the forum for haynes manual and youll find a thread with a link to a load of manuals. Theres a whole load of service info in one of the folders.

If your working outside see if you can borrow a gazebo or get a clean tarpaulin to throw over the tractor if the weather turns sour
'66 880 Selectamatic rat.

Gard
Posts: 211
Joined: Sun Apr 06, 2008 2:25 pm
Location: Fairfax Vermont USA

Re: Spun bearing on 990

Post by Gard » Sat Apr 20, 2019 11:23 pm

I do not have much experience rebuilding engines but would assume you will need a new connecting rod. I think you should be able to measure the crankshaft diameter to see if it is within spec (from service manual). Might be a good idea to pull the pistons out and try to get an idea of overall cost before proceeding. I have no idea if your head is original or not.

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