Piston Rings [Archive] - VW T4 Forum - VW T5 Forum

Piston Rings

Barry Coast
17-07-08, 17:46
I was wondering if anyone could tell me if I have to completly remove my engine to change the piston rings? My van is a 1994 T4 1.9 4 cylinder diesel. Is it not possible to remove the cylinder head and remove the pistons and con rods from the top of the cylinder? :confused: Baz

17-07-08, 18:12
I was wondering if anyone could tell me if I have to completly remove my engine to change the piston rings? My van is a 1994 T4 1.9 4 cylinder diesel. Is it not possible to remove the cylinder head and remove the pistons and con rods from the top of the cylinder? :confused: Baz

Hi i have used this method on several bus engines when i worked as hgv mechanic .Should be posible if you can remove sump:)

Barry Coast
17-07-08, 18:23
Hi cheers for the help, I can remove the sump but im not shure if the conrods will fit through the cylinder bore, ive got a manual and it says that its not possible to change the rings without removing the engine, but it coesent say why ?

paul ss
17-07-08, 19:16
why are you replacing the rings just out of curiosty

17-07-08, 19:20
cant you pull the pistons down out of the cyls?

paul ss
17-07-08, 19:25
well am asuming the crank would b in the way lol unless you knock the gudgen pin out but i wouldnt persnoly do it ,

what you have to ask yourself is why they have gone and is the block damaged or scored in any way if so replacing the rings shant do naff all are you sure they have gone

Barry Coast
17-07-08, 19:29
my t4s using loads of oil about 5 litres every 1000 miles, thers no oil leaks, at first i was going to fit new valve stem seals but a friend told me the rings were probly worn, i planed to remove the head and sump with the engine in place, then undo the conrod end caps
and push the pistons and rods up and out the top of the bores, is this possible?

17-07-08, 19:32
aye sorry I wasnt thinking right, of course it will!! unless you remove it, which means g/box out, so you might aswell remove the engine....D'OH!!!

paul ss
17-07-08, 19:34
i would check your turbo is spot on aswell

yes you can undo rod bolts and pull pistons and rod through i wuld just double check before you start removing them what i always do is remove thge head and pour some petrol on top of the piston see if it leaks ,

have you done a compreshion test that will reval a lot without stripping it down T:

Barry Coast
17-07-08, 19:39
yeah thats a good idea , my vans not got a turbo ,i can borrow a commpression tester any idea what the preshure shoud be? could any thing else be causing this problem,a blocked breather maybe?

paul ss
17-07-08, 19:46
am not sure what the compreshion should be to be honest but am looking all over the net as i want it myself , aslong as your pretty even across all cylinders thats the main thing

my experince isnt vast on deisels but there isnt a great deal that can go wrong on deisels from what bit i do no most of it works on presure

list of things t could be but which are very doubtfull

afm but would asume this with poor running as controls fuel more than anything

valve stem seals like you said yourself or a breather pipe
are you getting any smoke out the exuast that you dont normely get does it smell odd when running from exuast

Barry Coast
17-07-08, 21:36
yeah a friend was following me at the weekend , he sed when i put the engine under load he could smell burning oil, but thers no big smoke cloud on stsrt up.

Mr Big
17-07-08, 21:54
Think you need a cylinder leak test too. This pressurises the cylinder and measures if the pressure drops. This is the best way to test your rings before stripping everything down.

Barry Coast
17-07-08, 22:07
how does this work, ive compression tested petrol engines before when you remove the spark plugs, do you have to remove the heater plugs to connect the tester?

18-07-08, 18:34
Compression testers for diesels are more substantial than petrol testers as they have to screw in. We have one at work that through the use of adaptors replaces the injectors.

As to re-ringing the block without removing it, I’ve just done this. I had to fit a new cylinder head as the cambelt snapped on the previous owner and destroyed the original head so I took the opportunity to fit a new set of rings and a set big end bearings.

Remove the head & sump then mark your rods (1-4 1 being on the belt end & 4 being gearbox end) so that you put them back in the same order. Also mark the piston crown (top) with an arrow or centre pop to indicate the front (pulley/belt) end of the motor. Hone/glaze bust the bores. Once honed run your finger nail up the bore if you feel a ridge (about 10mm from the top) then you have wear. If so get an engineer out to measure the bore for you (you’ll get away with .001” per inch of bore so .003” - .004” wear…I know of some that re-ring with up to .006” wear). You need to order new big end con-rod bolts from VW as they are a stretch bolt.

You’ll need: a head gasket set head bolt set, a sump gasket, a ring set, a big end bearing set, 8 con-rod bolts, some assembly grease (Graphogen) a cam belt and tensioner (you may as well whilst you’re about it), oil & filter, coolant/antifreeze and a lot of patience.

Good luck and keep smilin :)


Barry Coast
19-07-08, 09:02
Cheers for the advice chris, :)

19-07-08, 09:47
with diesels a compression of around 400 psi, maybe a little lower will pass as okish. as mentioned as long as they are within 10-15 percent and not any lower than mentioned you should be right. could be ring lands, when they let go you'll chew oil as well. pull it down and inspect EVERYTHING closely for any damage
Good Luck


26-07-08, 13:28
i have simalar prob on my van using about 5 liters of oil a weeek !!!!
i have replaced the sump gasket and crankshaft oil seal but though the leaks have stopped still using loads of oil.so looks like i will be stripping mine down to replace the rings and valve stem seals soon.

bit of advise when you take the sump off there are two hidden bolts at gear box end you have to turn flywheel to locate a slot to be able to get these bolts out.