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Changing 300 TDi valve stem seals with head on


Peaklander
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With thanks to Cotleigh Crasher I have changed the stem seals on my 300 TDi, with the head on. This is to try to eliminate the start-up blue smoke that can be a little embarrassing as I leave the drive.

I know that this is a relatively simple job but for people like me it feels like a major one - the first time you do something new it always does doesn't it?

First job was to fabricate the tool with the help of a vice, cutting disc, and file

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Removed the air filter, rocker cover, cyclone breather and glow plug cables.

Then as I intended to spin the engine using a ratchet in the crank bolt, I thought that removing the glow plugs would help by reducing the compression.

#1 was easy to undo but #3 and #4 were very tight. I persevered with penetrating oil and turning slowly to and fro but as I removed the third one I realised that the thread had picked-up on the head as I removed. So I was wishing that I hadn't. I decided to leave #2 well alone. However two of the three that I did remove don't work. (tested by putting battery volts across them).

So with three plugs out I could move the engine rather than moving the vehicle in gear.

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Next remove the rocker shaft to provide access to the valve springs. Need to remove the little valve top caps (that touch the rocker arm) at this point. Mine were all in perfect condition.

The two valves on each cylinder can be changed with the engine in the same position - TDC. So I started with #1 and moved the crank pulley until that cylinder's exhaust valve had just closed and the inlet was just opening. Did this by watching the push rods. This is the end of the exhaust up-stroke with the piston at the top of the cylinder. There's only a mm or two between the piston and the valve at TDC so no worries about the valve dropping when the collets are removed.

The 'head-on' tool is used as a lever to press down onto a valve cap. You place it either on one of the three studs that are there for the rocker cover

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or by using another bit of 8mm stud, you can screw into one of the bolt holes.

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Which one you use just depends on the valve you are working on.

The exact angle of the tool can be adjusted by the amount of packing you use to protect the edge of the head..

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Screw down onto the tool and watch the valve stem come up through the fork part. As it does just tap down on the valve cap to release pressure on the collets.

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You do need to ensure that the tool fits around the valve as there needs to be room to completely free-up the two collets. One can get stuck under the tool.

Pack some rag around the push rod holes so that nothing can drop down there (collets).

Once the collets are properly visible they can be removed - and a magnetic pick-up is really handy at this point.

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Then remove the tool.

(note photos aren't necessarily always of the same valve)

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Now unscrew the tool and remove the valve spring

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The old stem seal is now visible and can now be removed - this is rather crude as I don't have the correct pliers but they are to be scrapped anyway.

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Next, have a bit of a clean-up around the stem and then put a little oil on the new seal. Fit it by using just a little pressure to push it down onto the valve past those collet grooves.

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As the piston is at TDC, both valves can be serviced in this position.

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Then re-fit the tool and as it says in all the manuals, refit is the reverse of the above sequence. So squeeze the spring, pull the valve stem up if it has dropped a little (the seal will hold it).

Be sure to fully compress the spring and keep the tool centred so that refitting the collets is easy. They fit narrow end to the bottom.

Once both valves on that cylinder are done, turn the crank and move to the next one. Just don't forget to get to TDC on that cylinder otherwise the valves will drop when the collets are removed (although i don't actually know how far they will fall or if they would fall too far).

Finally replace the rocker shaft and re-set the tappet clearances (0.20mm / 8 thou) when cold.

It doesn't take too long to do this whole job, just a few hours - for me the glow-plugs were far more of a problem. Fortunately the new ones screwed-in quite tightly so they seem ok.

Not quite ready to move the vehicle yet but hoping for a cleaner exhaust at start-up. :unsure:

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Worth remembering that TDC on number 1 is also TDC on number 4, and likewise, 2 and 3 - it might save some engine rotating. :)

Your smoke may be in part glowplug related. While a healthy Tdi will start quite happily without them in most circumstances, I understand that the glowplugs will continue to run after the lamp goes out and the engine is started in order to help reduce smoking when cold.

Nice writeup.

Cheers

Chris

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Worth remembering that TDC on number 1 is also TDC on number 4, and likewise, 2 and 3 - it might save some engine rotating. :)

Your smoke may be in part glowplug related. While a healthy Tdi will start quite happily without them in most circumstances, I understand that the glowplugs will continue to run after the lamp goes out and the engine is started in order to help reduce smoking when cold.

Ha! I'm old enough not to be too proud to admit that I totally forgot about the pistons moving in pairs! It was only when I finished that I remembered.

Yes I thought the same about the glow plugs. If the engine needs an extra turn or two before it starts without them then there must be a bit of extra fuel in there that isn't required. So I will be looking for a reduction in that puff of black as well as the blue.

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Thanks for the replies but they might need editing. :o

I've had a bit of a 'mare this afternoon. Having done the job described, I did some oil changes and was then able to start-up. There was a lot of blue smoke - more than before. I let it idle and revved a little once or twice. Even as the water gauge started to move off cold there was still blue smoke.

I'm not in a position to drive it at the moment so am relying on idle and a few revs. to check it.

So I stopped, had a think and looked at a few pics and youtube videos.

Decided that I hadn't pushed the seals right down the stems and onto the head - onto what ever they touch at the bottom that stops them moving up the stem.

Removed the rocker cover and I could see at least one seal that was high up.

So I repeated the whole job (remembering this time that only two engine positions are needed!). Here's a pic of one of the seals out of position:

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I pushed it down by hand and tried to feel a "click" as it connected with the head. I did this for all eight seals.

Put it all back together - and it's still the same - belching out blue. What have I done wrong?? Wracking my brain but it's not helping. (They are LR Genuine seals which I recently purchased from LR Series).

Any help will be very gratefully received!

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It's not the bores making the smoke, it will be the residual oil in the exhaust post/downpipe burning off.

Or at least that's what I very much hope!

Valve stem seals do need to be pushed pretty well home, or the valve spring retainer can contact them and damage the seal. Hard to see if your is damaged or not.

I think I have used a ~10mm socket on RV8s to do the same, was a nice fit, and they do push fully home and go 'solid', if you have pushed them on a little bit that may not be enough.

Do like the mehotd though, very much, well done!

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Tomorrow I'll top up the engine oil (ran out yesterday during the service). Still got to do gearbox oil, front axle oil and have a look at a leaky swivel seal (only been on a year max), then I'll give it a whirl.

If it's still NBG then I'll do the job one more time, check each seal and give them an even harder push. I was a muppet the first time round; don't know what I was thinking of just pushing them down the stem. After all it needed quite a tug to pull off the old ones.

Do like the method though, very much, well done!

Well as I said at the top, all credit for the method goes to Cotleigh Crasher (and for the 5mm metal piece from which I made the tool it's Twiggs at Matlock who sell their metal offcuts which they hold in a box near the office!)

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  • 1 year later...
On 17/04/2016 at 8:12 PM, Peaklander said:

Put it all back together - and it's still the same - belching out blue. What have I done wrong?? Wracking my brain but it's not helping. (They are LR Genuine seals which I recently purchased from LR Series).

Any help will be very gratefully received!

1

@Peaklander did you solve your blue smoke affair? Did pushing them down a bit further help in the end? With these cold mornings I think I'm getting the same issue with my seals (187000 miles on them) and would rather not take the head off if I don't have to!

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Hi I saw your question earlier but was trying to find another thread in which the discussion continued. I couldn't find it from my iPhone and thought I would be able to from base but I can't!

The gist of it is that some seals refused to locate at the base of the stem and someone on here (in the other thread) suggested a loctite variant to hold them in place. This is what I did and that worked. Meanwhile I talked to Freida Turner at Turner Engineering and she said that on a 300 TDi head, due to the shape of the casting, there was little chance of significant oil gathering in the base of the stem where the seal locates (and thus leaking through to the compression chambers and burning to create the smoke). In fact she said it was far more likely to be another cause and not even blue smoke that I was seeing. (Engine was at about 100K I think). She also said that it was very hard to find good quality seals and even though I had got genuine ones it didn't automatically mean their quality was good. They had come from LRseries.

The excessive blue smoke that I had seen on completing the job was due to the seals not locating properly, that's true but I never did get rid of the blue ting which seemed worse at a frosty morning cold start.

In fact the single biggest improvement I made, was a slight advance on the timing, from the standard position obtained using the timing pin (9mm drill bit) into the pump. I had read that over time there is wear on the contacting surfaces between pump and cam and as this develops over time, the effect is to slightly retard the timing. So I reset it using a smaller drill bit which makes for a looser fit in the hole and so allowing a slightly further twist clockwise of the pump (advancing the timing). This seems to reduce smoke generally and to be honest this probably had more of an effect than any work on the stem seals!

 

 

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  • 4 years later...

Hi.

 

Great tutorial, thanks for putting in the effort to do the write up. 

 

I followed this method to replace a broken valve spring. 

  • Thanks 1
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