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Minifinity The Classic Mini Forum and Resource | • View topic - compression test results what do they mean

compression test results what do they mean

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compression test results what do they mean

Postby 8ball » Mon 27th Nov 2006, 02:38pm

1=furthest from radiotor

1.=10psi
2.=9psi
3.=0psi
4.=13psi

i think its probably head gasket am i right

bought compression tester from halfords for 19quid and ran test myself

i also get brown gunk in top of rad water

thanks
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RE: compression test results what do they mean

Postby minimaniac » Mon 27th Nov 2006, 02:57pm

Are you sure you are doing the test right or reading the results in Bar rather than psi because with compression figures so low the engine shouldn't run at all!
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RE: compression test results what do they mean

Postby Dino » Mon 27th Nov 2006, 03:00pm

Actually no. 1 cylinder is the nearest to the rad - you've numbered them backwards!
But anyway these figures are terrible..really terrible..as in... really really terrible.
You should get 150-190psi
Even with a blown head gasket you should get a lot more than this maybe 50?
Normally when the gasket blows you get say
1=180
2=50
3=70
4=160
In this case it's blown between 2 & 3 - ( the most common.)

Are you positive you're using it/reading it right??
You should remove all the plugs,
screw tester in - make sure the rubber 'o' ring is a snug fit.
open the throttle all the way
crank engine, the reading should stabilise after a few secs.
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RE: compression test results what do they mean

Postby Dino » Mon 27th Nov 2006, 03:02pm

Oh, the brown gunk does suggest it may be the head gasket BTW
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RE: compression test results what do they mean

Postby Stoo » Mon 27th Nov 2006, 03:02pm

Those reading better not be in PSI !!!!!!

Anyway I'll base this answer on you getting your units wrong. Yes you have no compression on number 3 cylinder.

Does your rad bubble a lot when running with cap off or a lot of steam in the exhaust (heavy water consumption). If so then the likelyhood is you've blown the had gasket. (You'll probably find white mayo in the oil cap too).

If not then you could have a valve problem. Burnt valve, something stuck in it etc etc. You could also have damaged rings/piston.

...But first of all check the readings on your guage.

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RE: compression test results what do they mean

Postby Stoo » Mon 27th Nov 2006, 03:03pm

you sods beat me !
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RE: compression test results what do they mean

Postby 8ball » Mon 27th Nov 2006, 03:03pm

ok those readings are bar

by throttle all the way open do you mean gas pedal to the floor and i only took out the plug i was testin
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Re: RE: compression test results what do they mean

Postby minimaniac » Mon 27th Nov 2006, 03:16pm

"8ball"]ok those readings are bar


That's a relief!

Take out all the plugs and try it again. Number 2 (your number 3) should at least show some reading even if there's a hole in the piston! Once you've tried it squirt a little oil (not a lot) through the plug hole and try it again. If it improves then it's normally the piston rings, if it doesn't then it's a valve or gasket problem.
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Re: RE: compression test results what do they mean

Postby alloying » Mon 27th Nov 2006, 04:09pm

Dino wrote:Oh, the brown gunk does suggest it may be the head gasket BTW



Yep, also check for water coming out of the exhaust and A LOUD "CLANKING" UNDER LOAD!!!!
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rhubarbin gr8

Postby 8ball » Mon 27th Nov 2006, 04:17pm

tried the oil thing and psi increase from 10 to 50 on 3 tried it on 4 aswell now my gauge wont work and my car wont start if i hav the spark plug in 4

wot the rhubarb do i do now
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RE: rhubarbin gr8

Postby alloying » Mon 27th Nov 2006, 04:23pm

8ball, when it was driving did it "clank" under load i.e. when you put your foot down????????? (I've asked you about 4 times now).
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RE: rhubarbin gr8

Postby pablo » Mon 27th Nov 2006, 04:33pm

Just for reference, your original readings in psi are approx;

4. 145
3. 130.5
2. 0
1. 188.5

1 bar is approx 14.5 psi
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RE: rhubarbin gr8

Postby 8ball » Mon 27th Nov 2006, 04:52pm

8ball, when it was driving did it "clank" under load i.e. when you put your foot down????????? (I've asked you about 4 times now).


sorry mate dont think it clanks is definatly noiseyer and has lost power struggles up hill

latest readings are

150 psi
130 psi
10 psi
190 psi

with drop of oil in spark plug whole 10 psi increases to 60

have managed to start car now even tho i carefully labelled the leads i put 3 and 4 the wrong bloody wrong way round wot a numptey
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RE: rhubarbin gr8

Postby alloying » Mon 27th Nov 2006, 04:56pm

Hmn, what about a "ticking" noise? listen carefully to the cylinder with the bonnet open.
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RE: rhubarbin gr8

Postby ceejam » Mon 27th Nov 2006, 04:58pm

Either a sticking rocker/valve, burnt valve, or a hole in the piston!
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RE: rhubarbin gr8

Postby 8ball » Mon 27th Nov 2006, 05:04pm

how do i check the valves

Hmn, what about a "ticking" noise? listen carefully to the cylinder with the bonnet open.

it does sound like a ticking or tappin noise
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RE: rhubarbin gr8

Postby alloying » Mon 27th Nov 2006, 05:07pm

Sounds like a piston ring!
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RE: rhubarbin gr8

Postby 8ball » Mon 27th Nov 2006, 05:09pm

that sounds hard to fix or check is it
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RE: rhubarbin gr8

Postby Jimmyarm81 » Mon 27th Nov 2006, 05:15pm

You need to take the head off to see what is wrong.

It could just be the headgasket, they can fail in such a way as to create a 'one-way flap' between two cylinders, i.e. you will get a pressure reading in one but not in the other.
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RE: rhubarbin gr8

Postby 8ball » Mon 27th Nov 2006, 05:24pm

think ill go get a head gasket now how long does it take to do roughly ive got my haynes manual to talk me through it
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RE: rhubarbin gr8

Postby alloying » Mon 27th Nov 2006, 05:25pm

Took me about 5 hours first time round. Now I can do it in about 20 mins (lots of practice lol).
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RE: rhubarbin gr8

Postby alloying » Mon 27th Nov 2006, 05:27pm

Tip: the hardest part is trying to get the exhaust manifold off (especially if it's an LCB or freeflow), so undo the top engine steady from the engine and that should give you the clearance you need to pull the exhaust manifold out the way.
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RE: rhubarbin gr8

Postby 8ball » Mon 27th Nov 2006, 06:41pm

rite im gunna go and have a go now with with the help of a light and my brand new torque wrench. hopefully i can get it done tonight or ill have to finish it 2morra mornin b4 work
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RE: rhubarbin gr8

Postby Zippyrude » Mon 27th Nov 2006, 08:28pm

good luck
my guess is that if its your first one you wont manage in time. not meaning to have a pop mate, its just that if you do it well the cleaning up will take you a couple of hours alone. if you have the head off i would clean up the valves and reseat them as well.
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RE: rhubarbin gr8

Postby Zippyrude » Mon 27th Nov 2006, 08:29pm

oh and you will need feeler gauge to set the tappets / valve clearance.
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RE: rhubarbin gr8

Postby royallingham » Mon 27th Nov 2006, 08:44pm

It's more than just the head gasket - most likely a valve, better hope it's not rings or piston - but that would have blown much oil fume out the breathers. Best bet would be to get hold of another head - and just swap them over. Even that for a first timer is going to take a good few hours.
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RE: rhubarbin gr8

Postby 8ball » Tue 28th Nov 2006, 12:28am

am pretty proud of the cleaning ive done

im exhausted now so had to pack up but head is on and torqued up jus everythin else left to do now to put it back together

balls didnt do anythin with the valves part from clean round them some were a bit black will see how it is 2morra and next time i got a whole day will do valves if need be
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RE: rhubarbin gr8

Postby alloying » Tue 28th Nov 2006, 12:32am

Was the gasket blown?
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RE: rhubarbin gr8

Postby icklemini » Tue 28th Nov 2006, 12:42am

last time i seen this, i did a leakdown test and found that the rings were shot.. :\
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RE: rhubarbin gr8

Postby 8ball » Tue 28th Nov 2006, 12:45am

gasket seemed ok bit thin tho no damage i could see
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RE: rhubarbin gr8

Postby alloying » Tue 28th Nov 2006, 12:46am

Did you check the bores?
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RE: rhubarbin gr8

Postby 8ball » Wed 29th Nov 2006, 01:17am

if by bores you mean the were the pistons run then they were smooth as a babies bum no burns or anythin. was sum crap on top of pistons but clean that up inside the head was a little sooty will do another compression test 2morrato see how it is
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