compression and leak-down numbers on 3b - some advice please

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Hi Guys,
So I decided to do a couple of tests on the old girl due to the fact that I have a cold start problem (mentioned in earlier thread) and I plan on tossing in a turbo soon.
I did a compression test and a leak-down test, the compression was done with a Hastings (now JET) diesel tester and the leak-down with a Milton unit which uses around 40PSI to test.
Now the engine is a 3B, Sept 83 production, with 428,000 on it and nothing has been rebuilt.
Here are the numbers:

Cylinder............Compression.........Leak-down %........location of leak
......1.......................505.....................25....................Intake valve
......2.......................510.....................23....................Intake valve
......3.......................475.....................50....................Intake valve
......4.......................500.....................47....................Intake valve

I know that higher that stock numbers are also not good and I suspect that the numbers are higher because of the carbon build-up. I suspect that the valves are not closing properly also due to carbon and during compression (especially at that pressure) they get pressed in a bit more.
I have done the valve adjustments not too long ago, rebuilt the injectors, new glow plugs.
So does anyone know of a good, proven product that can assist in removing carbon build-up and not cause damage to the engine components?
Most of my mechanical experience is with gassers and in this case a little Methyl Hydrate in the fuel would clean up a lot of things.


Thanks in advance for any input.
 
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Well, during adjusting I set the clearances to spec, am I missing something? even if they are worn and you still have proper clearance, that should not be an issue with the valve going back into it's seat. If anything it would not go down as far, am I correct in this thinking?
Also I realize that the springs might be dying, but before I start flipping parts (which I don't have) and machining things, I want to see it I can burn off all the build up and do another test to see if I still has issues.
If you do find a source for new ones let me know - that type of info always comes in handy.
 
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Almost forgot,
During the compression tests, which I did with a warm engine, I took the advice on one of the earlier threads I read and disconnected the EDIC linkage, this did not work, since the arm on the pump at that point springs to the back of the engine (which allows fuel to be fed). With the 4 glow plugs out and the tester in 1 cylinder attached the truck actually tried starting, also since it was feeding fuel the readings were way off and the more I crancked the higher the pressure on the guage read. So I disconnected the wiring to the EDIC which causes the arm on the pump to be pushed to the front and there fore cutting off the fuel. Then it worked.
 

brownbear

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Well, during adjusting I set the clearances to spec, am I missing something? even if they are worn and you still have proper clearance,

When they wear, they get dished out. So your feeler gauge cannot read in the depths. So actually they may be off. Your feeler gauge would be across the pit.

When guys talk about machining them, it is to flatten out the surface again.

You can still set them up though, but you need a dial gauge and fix to firm to the engine and adjust it up and down the right amount of movement.

Probably the best bet slight of removing everything and re-surfacing them.

So answer is yes, wear will screw you up.
 

brownbear

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You can try smacking the valve with a plastic dead blow hammer a few times when doing the test too. Might clear up the obstructions with the valve. Smacking it compresses the spring and snaps it closed. We do this on piston aircraft engines when trying to diagnose a leak down problem. Don't do it too hard though. And use a plastic hammer.

Also run some seafoam for awhile in the fuel tank. But change your filter a few times.

Also you can do a good highway run, leave it in 3/4th and honk it along for awhile. Italian tune up they say. Blow it all out. Hot and fast.
 
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Ahh, the Italian tune up - quite familiar with that. Normally when I drive on highways I keep it around 3200-3300RPM anyways. I usually don't like pushing the engine past that, so you're saying more?
As for the hammer on the valve trick, I will have to try that, the only thing is to have a good strong shop vac hooked up to suck up whatever gets loose otherwise it might damage the rings.
In relation to the rockers - I can see that, but that would not cause the valve to stay open, it just would not go down as far.
I have heard of another trick which I am not too fond of: remove the springs, rockers, etc, put the valve in a drill and spin it to dislodge any build up or debris, the only issue with it is that you need to have a very good shop vac to suck everything up otherwise the debris might damage the rings. But that is a bit of a back yard rush job.
 
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you can unplug the edic when it's in the off position and it will keep the fuel shut off, or you can crack the lines to each of the injectors and let the fuel leak out while you're doing your test. The latter method is, of course, somewhat more messy.

Here's to a little diesel in your eye...

~John
 

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Well if I smacked it down a couple times on each valve I would not be too worried about the carbon pieces. i would just fire it up and let it pass.... But hey that's my thing, each to their own please. At your own discretion and risk.

I would not do the valve in drill thing myself.
 
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Brownbear, I would not do the drill thing either, I just heard about people doing that, as for the hammer on the valves, do you recommend doing it while the rocker assembly is installed or not.
Also I would like to find some additive that might help with cleaning out the system.
Anyone know of some products that help get rid of carbon build-up?
 
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ive heard about the valve in drill thing, dont you use a abrasive compound on the valve seat when you do that? (pulling the head off first of course)

why do you not reccomend this?

It might not hurt to pull the head off (although the wallet will hurt as new head gaskets definately arent a dime a dozen) clean the head out and check for cracks and loose precups, check for pitting and wear on the pistons and cylinder wall, and get a better look at the condition of the valves, maybe getting them machined some where wouldnt be too expensive (dont know myself). oh yea maybe new valve seals as well. sounds like lots but not too bad, and reasuring when you have it back together.
 
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Cody c - the trick I heard about was done while the head was still on the engine, personally that concept frightens me.
I am still in the hopes that I maybe able to remedy this issue without having to take anything off. If I was to remove the head I would do a proper job and rebuild it, but then of course is the next question, how long until the rings go and you get to do that again. I've had some engines where I've rebuilt the head and the bottom end was fine for a long time after, I've also had some that not even a year after the head, the bottom end went. So then you are faced with a question of, if you rebuild the head, should you do the entire engine, cost now vs cost later.
That is a choice I don't want to think about just yet :eek: :crybaby: , the compression is high so I think the only issue is the carbon build up.
So nobody knows of anything that gets rid of carbon build up? Is there no products out there that actually have been tried and work?

I want to thank you guys for all the suggestions so far, some of which I will definitely be doing (hopefully not the rebuild part :D )
 

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