18 replies to this topic

[mrmeds]

Hi, my 998 engine was rebuilt in dec 2021 by a well known northern mini specialist, and has jcg cooper  kit on it too, which dates from march 2020...

When engine was rebuilt, the previous fuel pump had leaked causing petrol to go into the oil etc. Was told needed new valves - when engine was rebuilt.

Felt it was lacking oomph about a year ago , and another more local mini specialist old me they thought it was lacking compression on one or more cylinders... so sent it back ,and it was declared fit ... with compression of around 180  across all cylinders.

Anyway , has been lacking oomph again -so as well as trying to sort out carbs, which have been set too rich by a local garage at some type- I deceided to do a compression test.......

 

results are  ( by the way my numbers are wrong way round )

 

1.   150

2.    125

3.   135

4,   140

 

 

assuming that as number 2 is more than 10% differnent , I have  problem . Assuming its unlikely to be valve or piston. ring as they are all fairly new...

 

head gasket ?

 

No signs of water in oil

 

 

[weef]

As I have just said in a previous post do a cylinder leak down test as a opposed to checking compression ratios to establish if you have a problem in this area.

[mrmeds]

so would need a leak down etster and a supply of compressed air ..... ? .....in which cas eits off to find a friendly garage !

[weef]

Yes thats about the size of it, make sure the garage has a good quality tester, as shown, one that operates at 100PSI, and work from the results you get.

[MrBrown]

Quick question: are your compression tests with the carb wide open?

[Avtovaz]

yes so the air has the best chance to be forced in.

[sonscar]

Have a poke at the tappets first as the added oil made little difference.Its cheap and easy to do.Steve..

[mrmeds]

Quick question: are your compression tests with the carb wide open?

yes

[mrmeds]

ok ... so I was topping up the dash ots with oil - so had an idea..... i used some  dashpot oil to run a line of oil along the join of the head and the block.... then started the engine ...

low and behold ... very fine bubbles appeared in the oil around the gap between spark plug one and 2 ..... when I increased revs ... bubbles got a bit bigger... so obviously a very slight leak in head gasket ..... is it enough to worry about , or should I wait until it becomes more of a problem -- bearing in mind I lack the skills to change my head gasket. ( not that i've tried  )

[Lplus]

ok ... so I was topping up the dash ots with oil - so had an idea..... i used some  dashpot oil to run a line of oil along the join of the head and the block.... then started the engine ...

low and behold ... very fine bubbles appeared in the oil around the gap between spark plug one and 2 ..... when I increased revs ... bubbles got a bit bigger... so obviously a very slight leak in head gasket ..... is it enough to worry about , or should I wait until it becomes more of a problem -- bearing in mind I lack the skills to change my head gasket. ( not that i've tried  )

Might be worth checking how tight the head bolts are.  I have in the past had a minor leak at one end of the head of a mini I just bought due to a bolt not being anywhere near to spec.

[sonscar]

A leaking gasket is unlikely to heal up and if left could burn a track in the head or block.As for skills it is not massively technical but does require some tools.Steve..

[cal844]

Fit a new head gasket (or get a garage to do this). It can be done in 2 hours (using buzz gun for removal then refitting and torque with calibrated torque wrench).

Time quoted doesn't account for head skim.

Edited by cal844, 17 July 2024 - 09:07 PM.

[MrBrown]

I’m with the others on this one. Check the head stud nuts and see if they’re all torqued to spec first. If you still have a problem after that, change the head gasket. Watch some videos on how to do it. No skills required. If I can do it, I’m pretty sure you can too! I use a little copper gasket spray on mine since I have had some issues with gaskets. If the head gasket does not correct the issue, it could need a skim.hopefully it’s just a not so tight head nut!

[mrmeds]

thanks ... will try torque first .... what am i aiming for.  40lb ?

[Lplus]

thanks ... will try torque first .... what am i aiming for.  40lb ?

My '69 - '85 Haynes says 50 lb/ft.  The pre '68 Haynes says 40lb/ft.  Personally I go for 50