18 replies to this topic

[mykweb]

Model: Mpi cooper
Year: 1997
Description of problem (please be as in depth as possible):


Hey all

quick question I am going to need to replace the small end bearing on my 4th piston. Firstly does anyone have a link to the part. I have tried looking on minispares and mini sport but can't find the thing.

secondly is it a hard job to get the old one out? do I need special tools or need to ream it in

Mike

[Dan]

No such thing!

The gudgeon pin is a shrink fit into the rod, and the piston rides directly on the pin. What is worn?

[MRA]

Hi Mike,

It is very rare for a 1275 engine to have a failed small end, as above there is no bush or bearing available for standatd 1275 rods only modified "H" section or small bore engines.

A typical failure mode for a 1275 small end is where the conrod has been over heated and once cooled does not return to it's original size and grip the gudgeon pin.

Did some one suggest it was a small end or is it your own observations, in which case please explain the issue/s ??

Edited by mra-minis.co.uk, 31 March 2011 - 09:04 AM.

[mykweb]

I will give you the full story

about 4 weeks after my engine was built I went ona drive. I got to fort william and my car let go. Could not figure out what the isssue was. Got it recovered home, stripped down the head to find the 8th valve was bent. I it has made a small mark on the piston, but not an indent.

Got the valve and guide replaced and all was ok.

A few months later when driving home along the motorway i accelerated to over take a car. I got a massive plume of white / blue smoke but the engine still had a good bit of go

Had a look at it on the weekend and found out the brake master was leaking and drawing fluid in the engine via the inlet manifold.

I srtipped the engine down to find my sw5i cam was nicely ******* and the brake fluid residue all over my block, case and gearbox.

I also had to replace the piston rings as they wer goosed as well.

Fitted the engine abck up with new rings, big ends, thrust washers, crank shells, original cam shaft.

Since doing this the car has been knocking. If I stick a screw driver on the block and press it against my head i can hear the knocking. When at number 1 cyl i can fainly hear it. But as I move along it gets louder on number 4.

As the car heats up it gets louder as well.

The engine still drives ok, pulls fine and no reduction in power. Tappets have been checked and rechecked.

Hope this helps

Mike

[AndyMiniMad.]

Did you check the rods were straight? Or the throwout on the crank? Very unlikely that the original failure has caused either of these but you never know! My guess would be the big end bearing on number 4. Cant give you a reason for this but what you describe (noise wise) suggests this. Is it possible you over/under torqued the caps? long shot I know.

[mykweb]

what the con rods. Yeah they looked straight and when laid down did not wobble.

I had the crank checked before refitting and was told it was ok.

I also tightened all the bolts to the torqueage showen in the haynes and rover manual.

One thing I did notice is when I was fitting the pistons back in the 4th piston was floppy. And by that I mean it rocked back and forth easily. Where are 1,2 and 3 had some resistance.

Could the Gudjeon pin be loose or cause this knocking

Mike

[ANON]

did you check the crank with a plastigauge?

[mykweb]

did you check the crank with a plastigauge?

I assume the guy who checked it did. I personally did not

Mike

[MRA]

what the con rods. Yeah they looked straight and when laid down did not wobble.

I had the crank checked before refitting and was told it was ok.

I also tightened all the bolts to the torqueage showen in the haynes and rover manual.

One thing I did notice is when I was fitting the pistons back in the 4th piston was floppy. And by that I mean it rocked back and forth easily. Where are 1,2 and 3 had some resistance.

Could the Gudjeon pin be loose or cause this knocking

Mike

Looked straight ?? you wouldn't be able to tell if there was a 2 degree bend unless you have a surface plate or similar to check them on, to say you laid them down and they didn't wobble could also mean that what ever you laid them on was warped and twisted as well

[mykweb]

Looked straight ?? you wouldn't be able to tell if there was a 2 degree bend unless you have a surface plate or similar to check them on, to say you laid them down and they didn't wobble could also mean that what ever you laid them on was warped and twisted as well

Hmmmm I am thinking about strippin it down and checking it out.

so guessing the possibilities could be con rod, big ends or crank?

is the gudjeon pin rulled out?

Mike

[Dan]

Not entirely, it's just very unlikely. If it was loose at the small end it would destroy itself very quickly, the piston would be rattling about in the bore or the pin in the end of the rod and the result of either at a couple of thousand RPM would not be pretty.

[MRA]

Not necessarily so, it could be loose enough to walk out but it would gouge the bore wall

[mykweb]

ohhh well guess what I am doing during the easter break

Mike

[MRA]

Eating Easter eggs ??

[mykweb]

Ok I decided to get the car off the road at Easter and have a look at what this

I have not used my car for a while and its sitting in the garage downstairs

I went out to start it today and it was ok

The knocking noise can't be heard that much when the engine is cold apers to get louder when it gets warmer

Mike