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 Post subject: New member with problems!
PostPosted: Tue Jun 25, 2019 10:44 pm 
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Hi, Thanks for the add. I have recently bought a 83 944 with 77k and a large history file. I knew it had a misfire when buying and was hoping it would have been a fuel or electrical fault but everything checked out. Carried out a compression test as follows -

No 1 - 185 psi
No 2 - 185 psi
No 3 - 150 psi
No 4 - 80 psi

So removed the head and found a burnt exhaust valve, had all valve seats re-cut, valves ground in and head skimmed. Refitted still the same. On inspection the bores looked fine.Waiting for a cylinder leakage hose to arrive but thought maybe the rings had stuck?? Taking the service history into consideration I doubt this, but the car has only do 20 miles in the last year. The previous owner owned it for 1 year, found the advert on facebook from where he bought it and that owner stated that the had run perfectly on a recent long return drive to South Wales. Before him that owner of 10 years covering on 4k miles spent 9k on servicing at porsche dealers and Indy's. Having the timing belt etc changed 3 times. The last having only covered 200 miles in 4 years!

I found a link to a post from a couple of years ago where a member had a similar fault on cyl 4 and was asking about removing the head and sump in situ. Has anyone done this or does anyone have any thoughts and ideas?

Cheers Mike


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File comment: Here she is.
944 1.jpg
944 1.jpg [ 77.97 KiB | Viewed 551 times ]
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 Post subject: Re: New member with problems!
PostPosted: Tue Jun 25, 2019 11:51 pm 
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that is a lot of loss for one stuck piston ring, but you can confirm this by putting some oil down the plug hole before a test, you can do this on all four for comparison.

did you replace the same lifters back in the same holes, you could have a completely jammed lifter?

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 Post subject: Re: New member with problems!
PostPosted: Wed Jun 26, 2019 12:32 pm 
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As Waylander said I'd do a Dry/Wet compression test. Dumb question but the valves on that cylinder are opening & closing aren't they? If you have a jammed hydraulic follower then that could do something.

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 Post subject: Re: New member with problems!
PostPosted: Wed Jun 26, 2019 5:27 pm 
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The wet / dry will prove if it’s rings or valves just as Jim says

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 Post subject: Re: New member with problems!
PostPosted: Wed Jun 26, 2019 9:43 pm 
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Thanks for your thoughts and ideas. I have done a cylinder leakage test today. Cylinders 1 and 2 were fine, 3 had a very slight amount but 4 was reading 40% loss, all appeared to be through the crankcase but when I refitted the oil filler cap and put my finger over the dip stick hole it all came through the inlet manifold. Which made me think it was a valve fault, even though the head has just been done. Finally I did a dry and wet compression test. Dry 85psi wet 205psi so it looks like the rings are goosed!!

Has anyone ever removed the head and sump and replaced rings with the block in situ? The bores did not have any scoring or damage.

Cheers Mike


Attachments:
File comment: Number 4 bore last week
65690072_348798352462522_2065766023973306368_n.jpg
65690072_348798352462522_2065766023973306368_n.jpg [ 233.73 KiB | Viewed 449 times ]
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 Post subject: Re: New member with problems!
PostPosted: Thu Jun 27, 2019 8:28 am 
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No reason why you could not do it

Just have to support the block while the front cross member is off, as you can’t get the sump off with the crossmember in the way

The rings could just be stuck, as there is no bore damage that would suggest they are not broken, I would dump some diesel down the hole and leave it to soak away then redo the tests

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 Post subject: Re: New member with problems!
PostPosted: Thu Jun 27, 2019 9:18 am 
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I the old days it was diesel/ATF mix but anything like that will work. Really if you re-ring it needs glaze busting so the new rings bed in.

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 Post subject: Re: New member with problems!
PostPosted: Thu Jun 27, 2019 3:44 pm 
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Is old boys know all the old tricks,

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 Post subject: Re: New member with problems!
PostPosted: Thu Jun 27, 2019 8:55 pm 
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I have tried soaking with ATF and the Snow foam for 24hrs each but this has made no difference. I have read on various sites warning against glaze busting or honing as it damages the Nikasil coating?? Engine building specialists who have done this many times say just fit new rings??


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 Post subject: Re: New member with problems!
PostPosted: Sun Jun 30, 2019 5:27 pm 
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Had a busy day, here is the offending no 4 piston. As you can see both rings are broken. Top ring on no 3 also broken. Time to make a shopping list.


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 Post subject: Re: New member with problems!
PostPosted: Thu Jul 11, 2019 11:00 pm 
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I'm surprised those broken rings didn't damage the bore, I had a 996 with a slight broken ring and it obliterated the bore surface.


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