paddocks and piston rings

I need to change my piston rigs as they have failed, well i say failed there is alot of crank case pressure, oil spitting out of the breather, blue smoke lots of it when cold, and it runs like a bag of spanners till warmed up.
Anyway on paddocks they sell piston rings for the 300tdi but it says they are for discovery defenders from 1984 to 1994. my car is a 1996 discovery 300tdi. They also sell piston kits ie pistons with the rings pre installed, with pin and circlips. is there any difference for the rings between 1994 and 1996. mine is on it thrid engine but believed to come out of a 1995 defender

Ho dear Alex, you don't think the bores are also worn, if they are, then replacing rings is a very short term solution to your probs.

Been there and done that...that's what I found 1000miles later back to square one.

Ok before you despair too much, it is possible for the head gasket to go between the cylinders and the pushrods and it gives a similar turn of events as you explain. Do you get pressure when you take the oil filler cap ?

What's the engine number start with? It should start with 16L I believe.

when i had the head off we found that the bores still had the cross hatching on them from when it had be machined, and showed signs of washing as they were very glazed. used a glaze buster, but it seemed to cause this problem.

GreenHornet said:

Ok before you despair too much, it is possible for the head gasket to go between the cylinders and the pushrods and it gives a similar turn of events as you explain. Do you get pressure when you take the oil filler cap ?

What's the engine number start with? It should start with 16L I believe.

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yep pressure at the filler cap

The engines are strong and unless its been running with too much boost due to stuck waste gate, or incorrect fuelling, the bores should last well into 250k territory.

Did you say the head is already off?

That's brilliant, if it I was petrol you can half that and less.

I would try water injection first,to see if it is ring gumming causing the probs-veg boys use W/I with great sucess

head was taken off june of last year due to failed head gasket. and head. replaced the valve stem seals, had acouple of the seats re-cut due to pitting, and all the valve relapped. Found alot of glazing on the bores hence why the were glaze busted. But like i said after that is when the smoking started well ittook around 2 months to start. Now first start is throws out clouds of blue smoke, and pops and farts for alittle while, one warmed up it hardly smokes at all, and runs lovely. It will stay like that until next day with other cold start. Breather pipe is sat in a bottle at the min(poor mans catch tank) and the hole in the air filter hose has been taped up. Also and i don't know why, put there is also pressure in the air filter and air filter hose, pushing rather than sucking. The air filter has been checked and cleaned as its the cylinder type of a 200tdi due to the snorkle, don't know why it has it as it came like this

I have run wvo mixed with diesel through it a few times, filter the veg oil through a 5 micron filter, and ran it 60/40 diesel to veg oil. The fuel pump has been turned up by some else, as i fitted this engine for the last owner a month before i bought it. power output doesn't seem to have changed much to be honest either, althou its doing around 22mpg

alex8882 said:

I need to change my piston rigs as they have failed, well i say failed there is alot of crank case pressure, oil spitting out of the breather, blue smoke lots of it when cold, and it runs like a bag of spanners till warmed up.
Anyway on paddocks they sell piston rings for the 300tdi but it says they are for discovery defenders from 1984 to 1994. my car is a 1996 discovery 300tdi. They also sell piston kits ie pistons with the rings pre installed, with pin and circlips. is there any difference for the rings between 1994 and 1996. mine is on it thrid engine but believed to come out of a 1995 defender

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pistons are the same if an stc number ,,dont buy rings other than 300 and dont buy cord rings ,glaze busting is a waste of time on a tdi honing can help if done well actual material removed not light surface scratches ,if you fit rings they need gapping in bores first then fitting to piston that going in that bore ,youd really be best measuring bore with a proper comparator ,just below were rings reach at top of stroke across the bore and compare it with the same at the bottom and fore and aft

jamesmartin said:

pistons are the same if an stc number ,,dont buy rings other than 300 and dont buy cord rings ,glaze busting is a waste of time on a tdi honing can help if done well actual material removed not light surface scratches ,if you fit rings they need gapping in bores first then fitting to piston that going in that bore ,youd really be best measuring bore with a proper comparator ,just below were rings reach at top of stroke across the bore and compare it with the same at the bottom and fore and aft

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what about the piston and assy including rings as they do standard 0010,0020 and 0030 at £24.99 +vat per piston. they also sell the rings standard oem again at standard 0010,0020,0030. I take it when you say the rings need to be gapped, and bore size meassured to find out if i need a standard ring or over sized

If the rings were at fault then that wouldn't cause the blowback to the air filter.(I could be wrong but don't think so lol)

Cracked head is my guess. They are susceptible to cracking between valve seats and injectors. If it is cracked then you will get smoke from burnt oil, blowback up the intake track and crap running until it warms up.

If it were me I would think Cracked Head.

On another note, when you deglazed the block, did you replace the rings?

On another another note, lol, when you have the head off again, check the height of the pistons. It is easy to bend a Conrod through water ingress, oil etc and not notice straight away.

Check me out, TDi guru lol - NOT

Where JM on this? He's the man.. SORRY JUST SEEN YOUR POST AS I WAS TYPING MADLY LIKE A TEENAGER THAT HAS JUST FOUND HIS DICK LOL

jamesmartin said:

pistons are the same if an stc number ,,dont buy rings other than 300 and dont buy cord rings ,glaze busting is a waste of time on a tdi honing can help if done well actual material removed not light surface scratches ,if you fit rings they need gapping in bores first then fitting to piston that going in that bore ,youd really be best measuring bore with a proper comparator ,just below were rings reach at top of stroke across the bore and compare it with the same at the bottom and fore and aft

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I'd no idea you could still get those things.

GreenHornet said:

If the rings were at fault then that wouldn't cause the blowback to the air filter.

Cracked head is my guess. They are susceptible to cracking between valve seats and injectors. If it is cracked then you will get smoke from burnt oil, blowback up the intake track and crap running until it warms up.

If it were me I would think Cracked Head.

On another note, when you deglazed the block, did you replace the rings?

On another another note, lol, when you have the head off again, check the height of the pistons. It is easy to bend a Conrod through water ingress, oil etc and not notice straight away.

Check me out, TDi guru lol - NOT

Where JM on this? He's the man..

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Lol any help is great.
first no rings were not changed.
The piston height past the block deck was 0.95mm
And as for the head being cracked i hope not as its the thrid one in a year lol.
first one was cracked
second to replaced turned out to be warped beoned repair
and this one at the time was in good conditiion lol

alex8882 said:

what about the piston and assy including rings as they do standard 0010,0020 and 0030 at £24.99 +vat per piston. they also sell the rings standard oem again at standard 0010,0020,0030. I take it when you say the rings need to be gapped, and bore size meassured to find out if i need a standard ring or over sized

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dont think about +10, +20 is were you start if block is worn unless its been done before then +40 ,10thou aint quite enough ,you only fit oversize pistons or rings to a block bored out to that oversize and then its not exactly +20 etc but actual piston size ,all rings are fitted into bores and gap measured before fitting back on piston if gap too small ring can break ,but first you need to see if bore is worn at its wearing areas,std pistons allways have std rings and if bore ok get oe

Sounds like you know your stuff dude..

I'm gonna stop typing now as I'm always too late lol

Ok just a quick update. started it up this morning, had br sat fort around 12-13 hours, started up, ran rough for about 2 seconds, and fine. No clouds of blue smoke, infact very little blue smoke. No checked for pressure in the inlet tracted yet, nor have i checked the breather to see if its still spitting oil. The only change is that i've not added any veg oil in it. just normal diesel.

Just re checked the tappets, and had to adjust 5 back to 0.20mm. its been said that maybe the reason the inlet tract is getting pressure beacuse of an inlet valve being burnt, or not seating correctly. Anybody think this could be a possibility. checked the tappets to see if any of them were to tight

If the valve isn't seating correctly then blow back would be present and give the same symptoms as cracked head etc.

If you have run the engine for a while with valves that haven't seated correctly, then there is a chance that the seats and the valves t he selves are damaged.

An engine always runs better older diesel when cold. Fact of life. Perhaps with veg oil there wasn't enough compression to run properly until warm due to open valve on compression stroke