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Solstice

New Member

• Oct 12, 2022

• #1

Chaps, I bought a diesel series 3 a while back, it wouldn’t run due to low compression (circa 130 psi) we, well mostly a mate with me handing him spanners! Did rings, head gasket, honed bores and lapped valves, compression was upto 390 psi and it started well.
I drove it to a local mechanic and performance was poor, 2nd gear up a fairly steep hill, when I got there it was difficult to restart, he did a compression test and all cylinders were down to approx 230 psi.
Any thoughts on what would cause a loss of compression on all cylinders?
Thanks
G

 

kermit_rr

Very

Full Member

• Oct 12, 2022

• #2

Why did you need to take it to a garage? Was there another problem?
Are you sure the valve timing is right and the tappets are set?

 

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Solstice

New Member

• Oct 12, 2022

• #3

It went to the garage to have the brakes checked over.
Nothing changed between recording 390 psi and 230 psi apart from a 5 mile drive.

 

kermit_rr

Very

Full Member

• Oct 12, 2022

• #4

I'd do another 'wet' compression test along with a leak down test.
If the pistons and rings were well oiled to help fitment, this could impact the initial compression test

 

kermit_rr

Very

Full Member

• Oct 12, 2022

• #5

I'd recheck the tappet clearances again, in case the rocker shaft etc is well worn

 

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Colthebrummie

Well-Known Member

• Oct 12, 2022

• #6

I reckon your original compression test was wrong, the second reading done by the mechanic is closer to what it would have been from the factory.

Col

 

S

Solstice

New Member

• Oct 12, 2022

• #7

Colthebrummie said:

I reckon your original compression test was wrong, the second reading done by the mechanic is closer to what it would have been from the factory.

Col

Click to expand...

It’s a diesel !

 

kermit_rr

Very

Full Member

• Oct 12, 2022

• #8

I thought compression should be just over 400, but I'm not a diseasel expert

 

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Colthebrummie

Well-Known Member

• Oct 12, 2022

• #9

Solstice said:

It’s a diesel !

Click to expand...

Oops, my mistake, I never noticed that in the original post. My teachers were right all those years ago, I must pay more attention.

Col

 

Bobsticle

De Villes Advocaat

• Oct 13, 2022

• #10

What head gasket did you fit?

Sounds like it didn’t like the trip much.

 

dag019

Well-Known Member

• Oct 13, 2022

• #11

I would agree with @kermit_rr above and do another "wet" compression test and see if you get the higher figures again.