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SD22 valve stem seals


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I'm planning on replacing the valve stem seals in my 720. My manual has nothing on the subject. Supposedly, it's simpler than taking the engine apart; just "messy" as one on the nissandiesel forum mentioned. Searching for the procedure and what would need to be adjusted afterwards resulted in nothing other than a possible source to buy the seals. Is it pretty straight forward once one has removed the valve cover and is looking at the valves? I assume I'd need a new valve cover gasket, and I have the spring tool with the rotary knob on top.

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You will need something to hold the valves from falling into the engine. I assume the diesel is somewhat similar to the gas engine. I set at BDC at the beginning of the compression stroke. Take the plug out, In this case the injector, and shove a couple of feet of nylon rope in, with a large knot on the end to keep it from falling in. Turn the engine with a wrench towards TDC and the piston will compress the rope tightly against the closed valves and hold them. Now compress the spring and remove and put the new seals on both valves. Grease the seals. Back the engine up to release the rope and go to the next.

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I would wear clothes you can throw away, everything having to do with a diesel engine is black, you touch anything that has had oil on it and your going to get black.

Unfortunately your likely going to have to pull the head unless you use air to hold the valve up, the rope method will not likely work, here is a photo of a new diesel head I bought a few years ago, it is just a bare head without valves.




See the small square hole to the right of the valves, the injectors are in a cavity on the other side of that hole, so are the tips of the glow plugs, one may be able to get a very small rope thru that square hole, but I would not bet anything I own on that happening, and if you actually did get it in the cylinder, it would take several feet if not yards of rope as that opening is only 3/16ths and the injector hole is even smaller, maybe an eighth inch.


See the square hole down there in the photo below.




This piece goes in the injector hole, remember I said the photo of the head is bare head, so this piece below is not in the injector hole and I seriously doubt that you could ever get it out from the top.




Also the hole in that piece is very small, the injector does not poke out into the cylinder or the cavity, it is squirted into the cavity right at the glow plug which is also in the way, see photo below.




Forget about the rope method, use the air method which I have never done using the glow plug hole if possible, if not then use the injector hole with the glow plugs in place.

Unless you know what you are doing with the air method I would pull the head, keep in mind that if you use the air method be sure to have the piston in that cylinder at the top you are working on in case the valve drops, you do not want to lose that valve into the cylinder.


First thing I would ask is why you think the valve seals are bad?

Edited by wayno
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I got a photo of the glow plug in there.




Here is that piece in the injector hole, I didn't put it all the way in because I would be afraid I could not get it back out, but the photo gives everyone a good idea why I think one can not use the rope method.



Edited by wayno
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Thanks for the tips guys. I'll go ahead and order the seals and gaskets soon.

Wayno, I'm guessing the seals are bad as it uses a lot of oil; a quart every 70 miles. It's also getting 40 mpg, presumably from burning oil with the fuel.

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Good info wayno, as always.


8 hours ago, datzenmike said:

 I assume the diesel is somewhat similar to the gas engine.


... and I was wrong.

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Does your truck/engine leave oil spots where you park it?
When you add oil and then start it does it make a large cloud of smoke that burns off after 10/20 seconds?

I am talking about a big cloud, my L20b in my work truck had so much blow-by that all the seals leaked(oil pan, valve cover, fuel pump, ect.), and when I added 2 quarts in the morning and started it there was such a large cloud you could not see thru from the oil getting by the valve seals for about 10/20 seconds that it was embarrassing, if I took a trip it burned/leaked 3 quarts of oil or more for each tank of fuel, I went thru a gallon a week just around town, the give away was when I added the oil in the morning, if I added oil the result was a cloud of smoke, if I didn't add oil there was no smoke.

6 hours ago, millican said:

Thanks for the tips guys. I'll go ahead and order the seals and gaskets soon.

Wayno, I'm guessing the seals are bad as it uses a lot of oil; a quart every 70 miles. It's also getting 40 mpg, presumably from burning oil with the fuel.


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Well if you not leaving oil spots(marking your territory) and it smokes worse just after adding oil then you are right, it's likely you valve seals are bad.

It's really a pain to remove the glow plugs and re-install them, but it's also a lot of work to remove the injectors, and when you do that you have to bleed the lines/injectors and it's still a pain to start.

I have never read how to use air to hold the valves in place, and it's a real pain to install the clips holding the valve springs in place, well a pain if your doing it yourself, I found it hard to get the clips out and back in as I used a fork for removing ball joints/tie rod ends, I found making a plate that mounted to extra cam towers I had made it a lot easier.

The first engine I used long bolts and a sleeve on one side to hold the plate at the right height, I used the rope method.


See the fork under the plate and on top of the valve spring.


It appears I didn't take a photo of the better setup I made when I did the second engine, the photos above are of an A block I put valve seals in, I sold them blocks after I got them running good on my engine stand so people could hear them run.

Edited by wayno
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I've used the air charged cylinder method on gas engines with good results, however you would most likely have to  make some kind of injector adapter to do it on a diesel?

If you try this method; when you have the cylinder pressurized take a socket and lightly tap on the spring retainer to loosen the keepers ( careful to not hit it so hard that the retainer releases the keepers all the way or you might get a face full of spring etc,) then use your spring compressor tool to release it all the way.  

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I once helped do a compression check on a SD22  and SD25 diesel, we used a adapter made to screw in the glow plug hole.

I suppose one could remove the guts of an injector and use an adapter on the end of it.

In the end one will likely have to make something like that adapter the guy rented from a guy that has his own Datsun/Nissan diesel forum, but that was to test compression not to add air into the cylinder, by the way, what stops the engine from turning, in gear with the e-brake on?

Edited by wayno
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No it is not a trick question, when we checked the compression on them engines(2 of them) we removed all the glow plugs, the engines turned over easy without any compression, so if one adds compressed air to a cylinder and the cylinder is at the top or near the top of the cylinder the compressed air is going to try to push the piston down.

I suppose I could have used a better word than turning, what keeps the piston from being pushed down when you compress the cylinder as you want it at the top in case when your pushing down on the valve spring trying to install the retainer clips that you don't accidentally push the valve down and loose it into the cylinder, I suppose the new valve seal will hold the valve and not let it drop into the cylinder.

As I said before, I have never used the air method, so I can see all sorts of stuff going wrong and I don't have proper tools made for the job.

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My wife offered to hold it for me. We'll see how that works.

So far, I've loosened the glow plugs, thinking I'll want to turn the engine at some point, removed the valve cover, and cleaned a lot. Mostly cleaned. I didn't know the engine was blue. I'm about to see if I missed something in the manual I have on what to do next. I have guesses, but not a head gasket.

If money were no object, something like this could be fun: https://www.jegs.com/i/JEGS+Performance+Products/555/3010/10002/-1?&mrkgcl=1239&mrkgadid=3338000898&adpos=1o3&creative=330726016703&device=c&matchtype=&network=g&jegspromo=nonbrand&gclid=CjwKCAjw7anqBRALEiwAgvGgm83wxtvXXlPrko0OCznorX9seek4oA4XIQFKRseUH_9Zr8H373bSrRoCyacQAvD_BwE&gclsrc=aw.ds

damn that long link. bad millenial web-scripting.


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There are way better motors than that, batteries alone would likely be over $15,000 for a good type like the Tesla brand vehicles have.

I figured out a few years ago it would likely cost around $30,000 to have an electric classic vehicle, the more you want(range/speed) the more it will cost, keep on mind this was a few years ago, things/costs may have changed.

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OK. I'm stumped on this. I want to find TDC for a cylinder, but don't have the timing marks on the pulley. So, I should be able to tell when it's near TDC by the movement of the valves' push rods. I just can't figure out which is the intake and which is the exhaust for a given cylinder.

Sure wish my pulley looked like the one in the book.

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I never really thought about this before. :lol:

Here is the back of both the single and double crank pulleys on my SD25 engines, they do have marks although I don't know what marker they should be associated with on the front case.


Here is the double groove pulley.


And here is the single groove pulley.


Here is my SD22 double groove pulley, I can find no marks/notches on it.



All you need to do is get the piston at the top of #1 cylinder with both valves closed, then you can do #1 and #4 cylinders, then turn the crank a half turn and do #2 and #3 cylinders as then them pistons will be at the top, if you have the glow plugs out spin the engine over by hand till air blows out of #1 cylinder glow plug hole, that will be the compression stroke on #1.

If you loose a valve into the cylinder it will be over with, you will have to pull the head.

I never really thought about this before, but when you remove the rocker assembly all the valves will be closed, you just need to make sure the cylinder your working on has the piston at the top, again if #1 cylinder is at the top so is #4, then half a turn of the crank and both #2 and #3 will be at the top.



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I have around 4 different OEM pulleys for the SD series diesel engines, one is a triple pulley, it came on a diesel truck with power steering and air conditioning.

I also have one water pump double pulley that someone made at home, I used to use it for the power steering but it kept wearing out the lower water pump/alternator belt so I used the other groove on the crank for the power steering.



You can see the belt aligns with the extra water pump pulley groove.


Edited by wayno
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Interesting. I thought you could get power steering or air-conditioning, but not both. Talk about luxury.

Also, I just drove the pickup around the block. Your trick of taking the glow plugs all the way out and feeling for the air flow made all the difference. The old seals were quite visibly larger in diameter around the valve than the new ones. It wasn't quite as messy as I was expecting. None of the springs popped off back into the pockets of oil. Now to see if it uses less oil.

Thanks again guys!

I lurk here but rarely have anything useful to say.

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