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300tdi started smoking and pressure in rocker cover


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Hi all, I hope someone can help!

1997 Discovery 300tdi 89000 miles.

Came off the motorway yesterday and stood at the lights the discovery started smoking.

Only a little at first but did get a lot worse.

Managed to get home and it had used a little oil, from full on the dipstick to around half way.

Checked all hoses and no blockages or breakages. Smokes at idle and under load.

Checked exhaust and oil residue in there that wasn't there before.

Cleaned the cyclone breather too and put back together and still smokes.

With the engine running could hear air coming from the cyclone breather so thought there must be excessive pressure and removed the oil filler cap to check.

When you remove the oil filler cap there is a lot of pressure escaping but the smoking stops.

Had to pick the BH up from the hospital so taped a bag over the oil filler gap hole to catch any oil and it ran fine with no smoke at all.

New head gasket around 8 months ago and no coolant loss whatsoever.

What would be the next thing to check?

Could it be valve oil seals or something more serious?

Thanks in advance!

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What colour smoke are we talking?

Mine did this, and it was the turbo dumping oil down the exhaust, as well as overfueling, so had a mix of blue oil smoke and whitish unburnt diesel smoke, depending whether I was idling or under load.

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Sorry for my short curt reply, as a New South Welshman I had to go and vote - In Oz voting is compulsory with a considerable fine to ensure a 100% turnout -- okay, there are two, maybe even three possibilities.

The first to check is the breather hose and plastic "T" piece that connects the cyclone catch tank breather hose to the turbo inlet pipe, remember the chamfered edge of the plastic Tee points towards the intercooler NOT to the turbo, this design is supposed to ensure that the oil mist is well mixed with the forced inducted air rather than being a aerated stream of oil mist.

If the tube is good and clear then the next thing to check would be the oil seals on the valve stems.

These can be checked without removal of the cylinder head but you must ensure that the piston of each cylinder you are checking is on TDC, that way you can remove the collets and springs - the valves being that close to the piston crown that they wont drop into the cylinder.

After renewing the seals re-compressing the springs is a hassle but using one of the rocker shaft bolts as a fulcrum I have done it, but its not an easy job, even so its better than removing the head.

BEFORE you fit new seals check for excessive movement of each valve in every one of the valve guides, you only need one worn guide to give you considerable volumes of engine oil fumes so check each one. There should be NO discernable movement of the valve stem in the guide.

If even one of these are worn then it's a head off job and get ALL new guides pressed in and this is not a job you can do in the average home garage. I'd also advise a new set of valves and have the machine shop re-seat the valve seats in so that your new valves seat perfectly.

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Hi and thanks for the replies.

Sorry for not coming back sooner, decided to take the head off to have a proper look.

As suggested the valve guide on two of the valves has noticeable wear so I think it will have to go for new ones!

This might be a stupid question but where would I take it? A garage or is it a specialist thing?


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I'd be looking in your Yellow (if in the UK you have such commercial telephone books) pages for a local engine overhaul workshop. To reduce costs you might want to supply them the parts such as a full set of GENUINE Valve guides, stem seals and valves. The genuine LR valves are sodium filled, I'm not able to comment on after market ones and in any case I wouldn't fit them in my engine.

A good engine reconditioning workshop will be able to :-

1.) Pressure test your head. It would be a terrible thing to recon a cracked head.

2.) Measure it to ensure it wasn't warped.

3.) Press in the new valve guides.

4) Re-cut the valve seats

5.) Fit the new valves with the new seals

And hand you back the assembled head ready for you to fit it. At this stage you WILL need a good torque wrench and a torque dial gauge. I would also advise you buy a new set of had bolts and a COMPOSITE cylinder head gasket.

Use compressed air to clear out any fluids from the head bolt hole tapping's. If you don't have compressed air use a flexible tube and blow like mad.

Don't worry that the hole in the gasket for the oil feed to the rocker cover is partially blocked off, it's supposed to be to restrict the oil supply to the rocker cover - it's a Land Rover thing :huh:

Take your time and torque up the bolts exactly as per the manual and then use the dial torque gauge for the final "stretching" of the main bolts.

There are threads on site to explain how to re-fill your coolant system correctly to ensure that you don't have any air locks.

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Thanks for the replies and as suggested took the head to be checked over and luckily (possibly) no problems found!

Head gasket replaced, head back on and tightened to sequence, valve clearances checked and engine started.

Everything seemed to run fine until I checked the engine over. Luckily I had not put the hoses back on and the turbo outlet (to intercooler) was pouring with oil.

Took the intercooler off and this too had a large amount of oil in.

Could this be the turbo seals pushing oil into the intake?

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I would say so yes.

Normally when that happens, people dont realise until its too late and the engine runs away with itself, drinking the oil for fun til its dead.

It just so happens that you've located the problem by accident after leaving the hoses off.

New turbo time Im afraid, unless you want to try the ebay special route and replace seals or the central cartridge itself.


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Finally found the (second )route of the problem!

The head gasket had gone which had forced exhaust into the oil system which caused the initial pressurised oil problem forcing oil through into the exhaust.

Head gasket replaced and the oil still pressurised but I noticed no exhaust with filler cap off. Planned on all the options from new turbo to valve seals, new hed etc and it turned out the hot exhaust gasses had cooked the cyclone!

£5 for a second had cyclone from my local indy and problem solved!

Can of turbo cleaner for good measure and better than new, no oil or coolant loss and most importantly, no smoke! :)

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  • 8 months later...

Hi, I have just put a new improved head on my 97 disco .It says use the new metal gasket on it instead of the other type. Reading replies to others who have changed theirs and not using the metal type I am a little nervous. Mine blue white smoke last week.I acquired the new head from padocks with new bolts. Its been on for 2 days now and running fine. I have a spare ellring one in case of an issue. Have had the fuel injector pump reconditioned 2 weeks ago and put new injectors on ,with new head. Mine has 351,000 klms on it. Do you think there will be an issue .Merry xmas to all. :blink:

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I've had similar problems with our rather well worn 300TDi. I thought the turbo was going because whenever I drove it "enthusiastically" I would get exhaust smoke shortly afterwards. Having lost my sister's car to a runaway turbo I decided to fit a brand new core, only £110 anyway.

Well once it was back on, new oil and all the other stuff they insist you do, the problem arose again.

To cut a long one short it tuned out to be the cyclone breather, the engine does breath heavliy and although it appears to be ok, when the engine breathes hard it was snapping shut and pressurising the crankcase and head, as you found, the filler cap is holding back significant pressure.

That shouldn't happen, and the effect was that the pressure in the crankcase was blowing oil from the turbo return out through the turbo oil seals. If you look closely at them they aren't really pressure seals and the main turbo bearing it what keep the oil pressure back, the oil flow is actually quite slow.

If it stops smoking with the filler cap off then you may have the same problem I found. I've disconnected the oil breather pipe from the turbo and fitted a new catch tank that then vents under the floor, excessive engine breathing is another cause of engine runaway so this prevents the chance of that happening.

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