15 replies to this topic

[HarrysMini]

While stripping my engine, I saw that the bearing for the big end on no. 1 piston looks to be distorted, like it's melted. I am guessing this is because of over revving but I can't say for sure.

 

Here are some pictures (hopefully you can make it out)

 

There's a mark on the con rod as well

 

 

Obviously, I will replace it along with all the other bearings in the engine. But is there anything else I should check? The crankshaft is quite scored so I will get that reground by 10 thou.

The engine has done 35000 miles but judging by the scoring on the crank, it can't have had many oil changes.

 

Thanks in advance for any help.

[Mini Mad Drakeley]

im guessing not too many oil changes either, if theres any noticeable ridges on the conrod then just smooth them out with abit of sandpaper to let the bearing sit completely flush, your already getting the crank reground so just get good quality bearings and your sorted i cant remember if mahle make mini bearings but their quality is very good

[mk1leg]

new oil pump whilst your at the stripdown stage......and the last to pic there fine just heat damage........get your crank reground and new big end and mains bearings use mahle barings are the best.......

[Gr4h4m]

http://www.studebake.../CL77-3-402.pdf

[HarrysMini]

Thanks for the advice guys, I was going to replace the oil pump anyway. It's false economy not to really.

Thanks for the link, that was very helpful and it confirmed what I thought was debris in the oil causing the extreme scoring on the bearings.
It doesn't seem to have a picture of the specific failure I have though, unless in missing it.

[Stevie W]

Hi,

From personal bad experience, if it is debris in your oil, the whole engine must be stripped and thoroughly cleaned including all oil galleries.
Include a strip and insepction of the gearbox as well.

My shells looked just the same as yours.

My experience of debris in the oil resulted in no oil pressure and a wrecked crank within 50 miles of getting my Mini back on the road (machining swarf in the oil galleries).
Ignorance on My part and the Guy who built the engine, resulted in the 2nd crank lasting only 500 miles before the same thing happened again.

I can't emphasize how important it is to have everything spotlessly clean.
The monetary cost plus heart break when you see your oil pressure gauge drop to zero and hear the big ends banging and the main bearings rumbling is almost too much to bear, especially after the second time!!!

Cheers, Steve.

[HarrysMini]

Hi,

From personal bad experience, if it is debris in your oil, the whole engine must be stripped and thoroughly cleaned including all oil galleries.
Include a strip and insepction of the gearbox as well.

My shells looked just the same as yours.

My experience of debris in the oil resulted in no oil pressure and a wrecked crank within 50 miles of getting my Mini back on the road (machining swarf in the oil galleries).
Ignorance on My part and the Guy who built the engine, resulted in the 2nd crank lasting only 500 miles before the same thing happened again.

I can't emphasize how important it is to have everything spotlessly clean.
The monetary cost plus heart break when you see your oil pressure gauge drop to zero and hear the big ends banging and the main bearings rumbling is almost too much to bear, especially after the second time!!!

Cheers, Steve.

Thanks, yes the engine is completely stripped, next I'm going to remove all the core/gallery plugs and take it to a shop and get it dipped in caustic and flush it through too get absolutely everything out of the engine.

 

I'm not going to do a gearbox strip this time round as I just want to get it on the road, but I want to put a 5 speed in there after a couple of years anyway. Do you know if I can clean and degrease the gearbox safely without stripping it? What bits will need lubing again afterwards? I'll clean as much of the sump and case as I can with Gunk and a pressure washer to get any bits of rubbish out of it completely.

[Stevie W]

I would just try and get as much swarf and bits out of the bottom of the gearbox as possible.

 

I think white spirit would clean and degrease well, but I would be worried about removing all the oil from the bearings and synchros.

 

Guess works on here (John I think) would be able to give you some very good advice on cleaning the gearbox...

 

Cheers, Steve.

[HarrysMini]

I would just try and get as much swarf and bits out of the bottom of the gearbox as possible.

 

I think white spirit would clean and degrease well, but I would be worried about removing all the oil from the bearings and synchros.

 

Guess works on here (John I think) would be able to give you some very good advice on cleaning the gearbox...

 

Cheers, Steve.

Yes that's what I was thinking, I don't want to completely dry out all the bearings etc. in the gearbox and end up scrapping it.

 

I will probably PM Guessworks when I get a chance to get an expert opinion.

 

Thanks

Edited by HarrysMini, 24 November 2013 - 09:01 PM.

[Jordie]

central oil pickup is recormended too if you havent got one.

 

http://www.minispare....aspx?pid=33191

[HarrysMini]

central oil pickup is recormended too if you havent got one.

 

http://www.minispare....aspx?pid=33191

Yes I would have liked one of them, but don't you have to remove the layshaft to fit one? 

[Icey]

Pfft! They are bearly worn in ;)

 

 

(Joking of course - those are from one of my old Honda engines)

 

The fear with a failure of bearings where white metal has been lifted is that it has to have gone somewhere. It'll be in the oil ways and more worryingly stuck to the crank. Because it's in the oil ways it risks blocking any of the smaller channels (e.g along the rocker shaft).

Edited by Icey, 24 November 2013 - 10:11 PM.

[HarrysMini]

Wow, those bearings certainly look well used!

 

Just another question, is there a way of cleaning out the oil ways in the crank, or do I get it dipped like the block?

[Stevie W]

I would say get the crank machined first, since the swarf generated by crank grinding and polishing could find its way into the oil drillings.

Then a couple of runs through a parts washer, before using compressed air to blow the oilways out

Cheers, Steve.

[Guess-Works.com]

You should use brushes to clean oil ways, don't rely on a blast of air....

 

google twisted wire tube brushes

Edited by Guess-Works.com, 26 November 2013 - 09:00 PM.