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Danny
02-16-2013, 07:34 PM
Hey everyone, I have a low compression reading in cylinder 1. The engine has a rough idle but rides smooth when on the gas. Did a compression test and found the low compression. I swapped the injectors around to see if maybe it was the injector causing the misfire but this is not the case. That is what lead me to the compression test. Think I may have a hole in the piston? Rings? Valves? I'm not sure if there is anything else I can do before I have to tear this engine apart. Can anyone help?

sailquik
02-16-2013, 08:24 PM
Danny,
What are your compression readings?
What devices did you use to take the compression readings.
Are the compression values for other 4 cylinders all pretty close and #1 is drastically lower?
Did you find any "black death" residue around the #1 injector?
Have you pulled the #1 glow plug to ensure it's sealed?
Read up on the process of removing the glow plugs as if you break them off you face removal
of the entire cylinder head to get the broken pieces out.
Take your time, use plenty of penetrating fluid, work the threads back and forth very patiently.
Roger

abittenbinder
02-16-2013, 08:40 PM
Hey everyone, I have a low compression reading in cylinder 1. The engine has a rough idle but rides smooth when on the gas. Did a compression test and found the low compression. I swapped the injectors around to see if maybe it was the injector causing the misfire but this is not the case. That is what lead me to the compression test. Think I may have a hole in the piston? Rings? Valves? I'm not sure if there is anything else I can do before I have to tear this engine apart. Can anyone help?

There is an easy, crude but effective cyl leak down test you can do yourself.

Cyl #1 is the easiest to test because the crankshaft pulley has an etched and labeled line across the width of the outside of the perimeter mass ring, labeled 'OT'.

This mark locates TDC of the #1 piston travel but it's up to you to determine if the valves are closed or if you need to rotate a further 360 degrees to have the cyl on 'firing' TDC.

Use shop air and a simple air gun and rubber stopper that seals the open injector bore.

Apply air pressure and a healthy cyl at 'firing' TDC will pop the gun/cork combo out of the top of the injector bore even with moderate effort to hold it in place.

IF it's easy to hold in place you can listen for the escaping air path to determine leak path. Oil cap opening hiss = piston or cyl damage, loud hiss at intake manifold opening = intake valve issue, loud hiss at exhaust pipe = exh valve issue.

Doktor A

Danny
02-17-2013, 12:06 AM
I didn't check the glow plug. I will check that. Thank u.
Doktor A. I would apply air through the center of the rubber plug?

abittenbinder
02-17-2013, 05:07 AM
I didn't check the glow plug. I will check that. Thank u.
Doktor A. I would apply air through the center of the rubber plug?

Yes. You're modifying your air gun to seal into the injector bore.

Once you located the pulley mark and lined it up with the indicator cast into the timing cover, try applying air pressure.

If the air gun does not pop out of the bore, turn pulley 360 degrees and try again.

IF neither position will contain the pressurized air, you likely have a mechanical issue.

To then find firing TDC, to aid in identifying the leak path, remove the vacuum pump to reveal the camshaft drive sprocket.

The drive slot for the vacuum pump is vertical when cyl 1 is at firing TDC. Then you can proceed with air gun for audible clues to identify the leak path.

Doktor A

Danny
02-17-2013, 04:37 PM
Thank u, I will keep u posted on the out come. Appreciate the help

Boater
02-18-2013, 12:33 AM
I got a leakdown tester to help me diagnose mine, it is unbranded and almost certainly of Chinese origin but looks identical to the ones used in many youtube videos of leakdown testing. Chances are they are not too expensive in US/Canada. The only place I could screw it into was the glow plug hole, I believe the injector hole is preferred but not really feasible with unthreaded injectors.

As Doktor A says a leakdown test is useful because you can listen to where the air is escaping - you will lose a little through the valves if you are not on TDC on the compression stroke, I found it took me a while to set most cylinders up right, but No.1 is much easier because you can use the timing marks.

You will be able to work out if you are hearing air escaping from inlet or exhaust, if you are pressurizing the coolant, or if it is coming out through the crankcase (may need to refit the rocker cover before you can convince yourself of this). It can't tell you whether air escaping through the crankcase is from piston rings or a piston hole so you won't be able to order parts before you take the head off, but at least you will have a much better idea of whether you should be looking at valve seats/seals, gasket or pistons/liners.

Definitely look up diesel leakdown test on youtube - it takes a bit of practise so watching a few people who know how to do it and interpret it can be pretty useful, it was for me anyway. One of the guys has videoed himself using a new to him tester on a customers broken engine with no practice run so you even get to see a couple of possible pitfalls as he gets the hang of it.

Good luck!

Danny
03-04-2013, 05:34 PM
Leakdown is done. I have air escaping into the crankcase. Looks like a rebuild or new motor here. Damn!!

Boater
03-04-2013, 07:08 PM
Pistons* and/or rings are cheaper than a head so it's not worst case scenario!

Good luck sorting it out.

*for one cylinder anyway.

Danny
03-04-2013, 10:39 PM
This is true. I'm gonna have to tear into it. Thanks for all the info. Sure helped a lot.
( do you think this could have happened because to much oil was put in ?)

Turbo John
03-04-2013, 11:12 PM
Leakdown is done. I have air escaping into the crankcase. Looks like a rebuild or new motor here. Damn!!

Danny I have done literally hundreds and hundreds of cyl leak downs on race engines and many street engines..
Cyk leakage % are all different for different engines.

Most race engines leak 2 -12 % The smaller the number the better. I have had some of my fastest engines leak 12-14 percent on 2 ring pistons. They ran fine.

All engines will leak some air past the rings and into the crankcase.....just depends on what the number is?

The leakage will go by the valves and rings. So just because you have air leaking into the crankcase does not mean its all bad.

Was the engine warm or cold?...big difference in those two readings as things expand with heat.

If you are in the 10-15 % area and all the cyl are the same then its not that bad.

"Blow By" the rings is common to all engines except some very expensive race engines with perfectly round cyl's and a special hone for a particular piston ring.

Dont throw the baby and bath water out together. Check another cyl and give us the percentages%? If you have big differences then its a problem.

Remember all engines will leak air past the rings and valves to a certain extent.

You can get a piece of carbon under a valve and it will leak like crazy but the valve job is still good....there are so many variables to a cyl leak down.

Make sure both valves are closed at TDC like Doc A says.

We used to leak different depths of the bores as sometimes something at tdc is good and .150 down the bore it was bad......

Dont freak out because you have air going by the rings. You should listen in a valve cover when its leaking 5-10%........sounds like a hurricane passing thru, but the engine is fine.

Engines are not perfectly sealed unless you want to go spend what NASCAR spends.:rad:

Boater
03-05-2013, 12:22 AM
Sorry, I had jumped ahead and assumed Danny would have tested all 5 (or 4?) cylinders in order to be able to differentiate more leakage on that one than the others. He has already used a compression test to make him suspect No. 1 though.

When I had head troubles (cracked) I also found a cracked piston (No.1) which I changed at the time. Wasn't running very smoothly after that so did compression and leakdown tests and identified 5 as particularly bad but all of 2 through 4 were down compared to 1 (no surprise there!).

The real surprise I had was after I changed the rings on the remaining 4 pistons and did a cold leakdown test, all cylinders were reading under 20% - on a 16 year old 205k mile engine. Still haven't had it properly warmed up to do it again and see how much better it is warm. They aren't race cars but Merc engines seem to be pretty hard wearing!

Trouble is all these tests rely on experience for interpretation, and I don't have much. What Turbo John says about major sounding air leaks if you are even a tiny fraction of a degree off TDC is true, I spent ages trying to get each cylinder to the best position - of course with a newly built head I could pretty confident that any unusual noise from a valve indicated dumb operator error rather than a real leak!
I'm pretty happy with my findings so far!

Danny
03-11-2013, 06:07 PM
Hey there. Thanks for all the great advice. Im gettin 20-25% leak down in cylinders 2 through 5. Cylinder one I'm gettin 80%. And I hear it goin into the crankcase. Nothing through exaust or the Intake. Any thoughts?

Boater
03-11-2013, 06:37 PM
Sounds like piston or rings to me, need to take the head off and use Mk1 eyeball from here on in.
Well, some internal calipers and a suitable mic to check the bores, but they are aids for the eyeball :D:

If you did the test cold 20-25% is probably good, if you did it warm it's not necessarily bad as long as they are all similar (within 5%), but you might want to do all the pistons first time so you don't end up with 1 cylinder better than the others (been there, second rebuild to change rings on the other 4!)

Danny
03-13-2013, 11:36 PM
It was a cold test. So I have the same thoughts as you do. I guess we'll find out when I open it up. Damn! Hopin its just the rings

lindenengineering
03-15-2013, 02:59 AM
Danny
First I recommend doing an oil analysis to determine what is in the oil.
I have just received a bad blowing Tinny & 2.7 litre engine in the shop.

I had a shot at it by scanner diagnosis and "exterior visuals", but held off on a tear down until the results arrived from Blackstone who I use a lot for my fleet customers to predict problem in the making.
www.blackstone-labs.com/

Results:- High silica in the oil--dust and dirt being injected which "crooked" the cylinders.
Evidence high %age of chrome, cast iron, alum (pistons?) copper and lead (engine bearings?)
Surprise for me it was low on carbon and suspended fuel which rules out bore washing!
So first I need to check the intake for rupture or leakage at the air filter clam shell cover. Then look to see if dirt is in the inlet tract etc before proceeding with the big stuff.

Also some notes on re-ringing etc. Do remember to de-glaze the bores for good bed down of the rings etc. I don't recommend it but the "dooberry ball" hone is often used by DIY er's and Pro mechanics a like.
Reason:- The factory cylinder finish is a plateau hone to about 35 to 42 CLA which gives the bores that cross hatch finish. This aids cylinder oil retention and reduces oil loss from pumping action reducing E figures.

CLA:- "Clear light average" Basically like placing a straight edge over the cylinder plateaus (plateaux??? ) Parlez vous Francais :laughing: And measuring the light passing through the valleys on the cylinder wall

What ever you do after first removing the under piston jets and honing is wash the cylinder bores with good old fashioned soap and water and agitate with a stiff nylon brush. This removes all microscopic traces of grit participates adhering to the cylinder hone valleys. After all you don't want these wearing your new rings on start up as they wash out with oil splash.
Once washed, I dry with compressed air and lube immediately with some fresh clean oil to avoid corrosion prior to assembly.
Cheers Dennis

Boater
03-15-2013, 03:18 AM
Hmm, I guess my deglazing with a scraper blade was inadequate then!

lindenengineering
03-15-2013, 02:43 PM
Hmm, I guess my deglazing with a scraper blade was inadequate then!

Boater
Nah mate, won't work!
You are harking back to the Albion Claymore days of the 1960's!
That's when I was snot nosed kid apprentice in Gloucester , and Scotsmen exclusively drove Albions (made in the Glasgie Yoker works) with a wee dog in the cab!:thumbup:

That's even when Bathgate works was a twinkle in BMC's eyes!:laughing:
Cheers Dennis

Danny
03-16-2013, 06:58 AM
Thank u for all the info. I will use it all. I have this engine almost out. The only thing holdin it back it the main wiring goin from the cab to the top of te engine. Is there an easy way to disconnect it? Seems like inside te cab is not an easy option. And on top in the motor I have to take out all the fuel lines for the injectors. Are these the only options?

lindenengineering
03-16-2013, 01:03 PM
Danny
Simply disconnect the engine harness at the ECM and thread it through the bulkhead (firewall) and you are ready to pull the lump out.
Dennis

Danny
03-16-2013, 01:32 PM
Ok. Wasn't sure. It was late and its a jumble of wires under there and wasn't prepared to start tearin wires out. Ill take another look at her. Thx

lindenengineering
03-16-2013, 01:48 PM
Danny
The main harness is split up into about 5 main socket sub sections all plugged into the ECM under the dash, They have U shaped locking hold down clips usually grey in colour.
Flip them across the socket head and they will self eject. You can't mix em up 'co they are all shaped differently but label them if you are unsure.

Then pull the rubber harness plug/grommet out of the firewall and then thread each bit of the harness out one by one into the engine bay.

Try it, its how the zombies on the production line installed it.
Dennis

Danny
03-16-2013, 01:55 PM
Haha. Sounds good. Thank you.

Danny
03-21-2013, 03:59 PM
Well. Engine is out. On the stand. Turned over and took off the pan. Don't c anything wrong from that view. Wondering if I should pull the crank and piston 1 or take the head off. What's the best plan u think? I haven't taken a head off of one of these engine before. So I'm a little leary on what order to take it off and messing with the timing of the cams

Danny
03-21-2013, 06:36 PM
Is there a tread on hea removal? I'm not being able to locate one. Just wondering if anyone knows where I can find detailed instructions on the removal and install. I have the manual but we all know how much fun that is to follow a project like this.

Danny
03-21-2013, 06:42 PM
Is there a tread on hea removal? I'm not being able to locate one. Just wondering if anyone knows where I can find detailed instructions on the removal and install. I have the manual but we all know how much fun that is to follow a project like this.

Danny
03-22-2013, 06:34 PM
Sorry. I ment a thread on head removal.

santucho
03-22-2013, 09:49 PM
Sorry it's in spanish, may help you

Danny
03-23-2013, 02:59 PM
Thank you. I do have that in english from the repair manual.

Danny
03-24-2013, 02:11 PM
Problem found!!!. I am not to sure why this happened tho. There is a piece of the piston broken off and fell out when I pulled it. Cylinder wall is still is great shape and has no scoring. Got lucky there. Just curious if anyone knows what this happened ?:idunno:

sailquik
03-24-2013, 02:50 PM
Has this engine ever been rebuilt?
I'm no diesel mechanic, (I leave that to people with more experience working on them), but I've built a lot of street and race gasoline engines,
and seeing the ring gap in the top compression ring nearly directly above the 2nd compression ring seems pretty wrong to me.
Normally the ring gaps are spaced so that no two of them are in line or even close to in line.
Better still with 3 rings (360 deg./ 3= 120 deg. ring gap spacing.
In a diesel with much higher compression ratio I would think that ring gap spacing would be even more critical but I will leave it up
Dr. A and the MB engine designers as to whether that contributed to this failure.
Roger

Aqua Puttana
03-24-2013, 02:54 PM
Problem found!!!. I am not to sure why this happened tho. There is a piece of the piston broken off and fell out when I pulled it. Cylinder wall is still is great shape and has no scoring. Got lucky there. Just curious if anyone knows what this happened ?:idunno:

51310

51311

Let's hope it works out with catching it soon enough.

Here's a couple links with some information.

http://www.boosttown.com/engine/piston_damage.pdf

http://www.thedieselgarage.com/forums/showthread.php?p=838834#post838834


I dug the links out of this thread.

http://sprinter-source.com/forum/showthread.php?p=184416#post184416

Maybe it will give you some idea. Good luck. vic

P.S. - Is that a Bud Light flask in the lower right of the picture? It doesn't look like a can or bottle.

Danny
03-24-2013, 03:06 PM
Thanks for the links. It has shed some light on y the piston cracked. It's just in an odd place . Typically the pistons crack on the crown and not between te rings. I guess I should get these injectors tested.

P.S. it's a piece of a bud light box I tore off to mix some puddy on early. Haha. A flask would have been cool

Danny
03-24-2013, 03:25 PM
i do have some other concerns. piston #4 has a matt look to it and the others are all glossy and clean. Not enough fuel? do you think I should take all the pistons out and re ring them all?

The picture of the head is of #1 and #2. number 1 is where I had the broken piston. the valves look quite dirty compared to the others ( probably because the piston was broken and oil may have been getting up there?).

PTChambers
03-24-2013, 05:07 PM
Im with Sailquik on this one. (I am also a gas engine guy, not a diesel guy). If those rings came out in the position they are shown, I would rering all of them unless you find specific instructions to line up the gaps on this engine (dont think you will). Chances are that the assembler paid no attention to the positioning of the ring gaps so I would be leery of the current ring job. I also dont know what the ring gap spec is on that engine but I bet those rings are out of spec. Any assembler who doesnt pay attention to the gap positioning probably did not pay attention to the gap spec and did not check or adjust them properly.

(I may be showing my gas engine roots here and diesels may be different but with the higher compression involved it would seem to me to be more critical)

Phil

Aqua Puttana
03-24-2013, 05:51 PM
To the best of my knowledge it is a myth that the piston rings cannot rotate under operation. Once there is a bad spot the rings may rotate until they get hung up on the rough edge. That can cause the gaps to line up even if they were originally installed in the recommended staggered orientation.

I have no idea what happened in this case. I'm just passing on information as I know it.

Danny,
Were I you, I would want to do everything that can be done to keep the compression the same on all cylinders. While it is apart I would replace all the rings. I'm not an expert on rebuilds though. vic

PTChambers
03-24-2013, 06:51 PM
Hi
While I am sure it is possible for rings to rotate, the engines I have torn down (that I put together or the factory did) generally had the rings as they were assembled (in the 120deg positioning for 3 ring pistons). During break in, the rings "seat" in and develop fine striations in the cylinder wall and the rings that while almost invisible, hold them in place without something major happening. This is from memory and may not have been true in every case but I cannot think of an exception offhand. The reason you "glaze break" the cylinder walls is to allow this to occur.

So I remain suspicious of the original assembler of that engine.

Aqua Puttana
03-24-2013, 07:58 PM
...
So I remain suspicious of the original assembler of that engine.
You are entitiled to base things upon your experience. I do it all the time. well... actually I use my experience, not yours. :dripsarcasm::dripsarcasm: I don't think there is enough evidence to blame or condemn the assembler of the engine. It may very well be OEM. :idunno:

Since my memory and knowledge is always subject to my aging memory, I did a search for you. These are some of the first hits. I didn't need to dig for the answer I wanted. FWIW. :cheers: vic


http://www.machineryspaces.com/piston-ring.html

To ensure adequate lubrication the operating temperature should not exceed 200oC and this requires the rings to be fitted as low down the piston as possible. Lubrication of the rings is essential as it is needed to reduce friction and wear to augment gas sealing Ring will normally rotate on piston due to the variation in gas pressure. A typical rate of movement is 1 – 3 mm per cycle

http://en.wikipedia.org/wiki/Piston_ring

It is considered good practice[citation needed] to build a new engine with the ring gaps staggered around the circumference of the bore. This means that any escaping gas must negotiate a labyrinth before escaping past the rings. However, while the engine is running, the rings will tend to rotate around the piston and not remain in the position as fitted. Many rings will then stick in one spot at random and remain there for the life of the engine. For this reason, ring position during build cannot be considered to be important although most engine builders would feel uncomfortable assembling an engine with the gaps aligned.

http://underthehood.mahleclevite.com/?p=803

To answer your second question… Crosshatch on the cylinder walls causes the rings to slowly rotate around the piston. This is a good thing as it helps prevent localized hotspots from forming.

Danny
03-24-2013, 08:00 PM
I figured I would do them all for that reason too. They can only have about 5 % difference in compression from one another ( from what I've read ).

PTChambers
03-24-2013, 09:01 PM
Hmmm, good references, Vic.

I cant argue with that very much except to say that my experience is different. However, I also must admit to age and my shop experience was 40 to 60 years ago (when I was a mechanic for my fathers auto shop). Ring material was not the same as it is now and engines required an overhaul at 50kmiles or so or even sooner. Many engines used "cast iron" rings that would be done by 20kmiles. The rare engine was one that went 100k with only one valve job. Glaze breaking was to allow the rings to "wear in" and they typically did not move. The cross hatching would disappear and be replaced by the vertical striations.

Looking at the cylinder pictures of this engine amazed me because they look like they just were put together. But an engine that is capable of several hundred thousand miles has to wear slowly so I guess I am not surprised that I was wrong, at least for current engines.

Boater
03-26-2013, 06:26 PM
I replaced piston 1 without re-ringing the others and then discovered the compression variation was out of range as a result of having one better than all the others, my second teardown experience suggests I should have just done the rings on the others at the same time.

It seems that with a timing adjustment it must have passed the smoke measurement for it's MOT today - just need to deal with the other elements which I'll start a new thread for.

For reference I staggered the rings on all my pistons by 120 degrees but they are very free to move and I honestly couldn't say with any conviction that they were still at 120 deg offsets by the time I had fitted them into the ring compressor and slid them into the cylinders, never mind how they might be if they slide around and settle in their own position.
Surely the purpose of gapping the rings (mine came gapped within the spec for my cylinders, probably because the cylinders were soo good) is to ensure that when the are squeezed up during installation and later some more due to expansion as the engine heats up that the ends will just butt together leaving no gap, but equally not forcing the rings to distort or the ends to overlap - which I think is why there is some doubt cast on whether staggering is actually necessary, personally though I couldn't not do it!

Danny
03-26-2013, 10:50 PM
Thank u for the tip. I did order all new rings and hopefully puttin them all in this weekend. I was wondering about the head bolts. They look fine but I know some engines they are a one time use. Does anyone know if I can re use them?

Boater
03-27-2013, 12:53 AM
There will be a stretch limit for the bolts, if they measure less they can be re-used. I have some info for OM601, OM602 and OM611 and the allowable stretch does vary so you will need to find out the value for your engine code.
My OM602 was well within after probably 200k miles, but I replaced them anyway.

Danny
03-27-2013, 02:08 AM
ok thanks. I figure that they're not that much anyway so I'll just play it safe and use new ones. Thank u

Danny
03-27-2013, 10:28 PM
So here's where I'm at. Engine completely disassembled. Parts on order. I thought that maybe this happened to the piston because of over fueling but I just had the injectors tested and all came back good. So that can't be it!! I'm being lead to believe that the piston just wasn't good. It didn't overheat or showed any sign of issues before this. I'm at a loss as to way this happened

talkinghorse43
03-28-2013, 01:32 AM
Each cylinder has a dedicated oil nozzle meant to cool the backside of its piston. Each nozzle is fitted with a spring-loaded ball check valve that prevents the nozzle from admitting air to the oil galleries when the engine is off and opens at ~20 psig oil pressure when the engine is running. If a nozzle does not spray cooling oil for some reason, then that piston could overheat during periods of high load.

Boater
03-28-2013, 01:52 AM
At the bottom of each cylinder is an oil jet which squirts oil on the underside of the piston which aids cooling. I decided not to check mine because when my injectors were tested they were all misfuelling to some extent (that may yet bite me!) and the information I found (I think in these forums from Abittenbinder or Altered Sprinter) put me off - If I recall there is a special tool for pulling and re-inserting the jets. Failure/blockage of one of these jets can apparently lead to a local hotspot which may blow a hole in a piston.

I was struggling to identify the damage in your photos but I do remember reading about another possibility regarding the gudgeon pin. If not fitted correctly the gudgeon pin can hang up and cause a stress concentration in the sides and crown of the piston which over time can lead to the piston cracking. Once again I found out about that from a thread here possibly with a link to a tech note from MB?

(TH43 beat me too it - I may have fallen asleep whilst typing...)

Danny
03-28-2013, 02:09 AM
Haha. Thanks. The oil sprayers I haven't checked. I think I read in a thread here that a homemade tool can be made to remove and install them. I will have to search for it agian. I wonder if they can be tested

talkinghorse43
03-28-2013, 12:43 PM
I think the good Doktor (abittenbinder) has written here about testing them.

Danny
06-25-2013, 09:55 PM
Hey there sorry about the late reply am finally back on the rrbuild got the block machined and the head. Got all the pistons in and crank just not sure what the next step is please help

Danny
06-28-2013, 03:10 AM
if anyone knows where I can find step by step instructions for a complete engine rebuild, it would be greatly appriciated. Thank you