1 reply to this topic

[Hewlett_T]

Hey,

 

A few days ago I did a compression test on my Mini, the results were:

 

Cylinder 1: 157.

Cylinder 2: 150.

Cylinder 3: 150.

Cylinder 4 120.

 

This far I have removed the cylinder head and done a water test on the valves and have seen no water escaping from them.
Upon inspection of the block there is a lip along the top of all 4 bores? Is this normal? it's about 8mm thick?

If anyone could help with possible causes or worst case scenarios and costs of repairs it would be a great help. I would also like to know weather the lip at the top of the bores means I would need to have it re-bored in order to make this perfectly flush, which would also mean replacing the piston rings?
 

Thanks.

 

 

 

[Cooperman]

The depth of the 'lip' shows where the top piston rings comes up to. Ideally there should be no lip and when a significant lip exists it will be necessary to have a re-bore and new pistons. If the lip is very slight, and I mean VERY slight, it might be possible to hone the bores and fit new rings, but this can lead to the engine burning oil after relatively low mileage and is often false economy.

The compression figure on no.4 does seem a bit low.

As for costs a rebore is considered a full engine rebuild and is usually combined with a crank re-grind or micro-polish, new main & big end bearings, a new oil pump, etc.

If you do the rebuild work yourself, excluding the machining, the parts will cost in the region of £400 plus machining at around £160 to £250 depending on how much is required (head skim, valve seats, etc.).