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What's wrong with my engine, head gasket or piston ring issue or......

2K views 28 replies 7 participants last post by  RaceDiagnostics 
#1 ·
So here is the story, the car has covered about 600 miles since its 3 year body restoration. Since there was a misfire on cylinder 1 before I put the car back on the road (oiled plug), I replaced the plug and just cleaned up the others. I did a compression test at the start of the year and the results all looked fairly good. This is what they now look like, what are your thoughts? I've never seen a plug like this before.




Cylinder 1
2604020


Cylinder 2
2604021


Cylinder 3
2604022


Cylinder 4
2604023


Cylinder 5
2604024


Cylinder 6
2604025


Cylinder 7
2604026


Cylinder 8
2604027
 
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#4 ·
So here is the story, the car has covered about 600 miles since its 3 year body restoration. Since there was a misfire on cylinder 1 before I put the car back on the road (oiled plug), I replaced the plug and just cleaned up the others. I did a compression test at the start of the year and the results all looked fairly good. This is what they now look like, what are your thoughts? I've never
So here is the story, the car has covered about 600 miles since its 3 year body restoration. Since there was a misfire on cylinder 1 before I put the car back on the road (oiled plug), I replaced the plug and just cleaned up the others. I did a compression test at the start of the year and the results all looked fairly good. This is what they now look like, what are your thoughts? I've never seen a plug like this before.




Cylinder 1
View attachment 2604020

Cylinder 2
View attachment 2604021

Cylinder 3
View attachment 2604022

Cylinder 4
View attachment 2604023

Cylinder 5
View attachment 2604024

Cylinder 6
View attachment 2604025

Cylinder 7
View attachment 2604026

Cylinder 8
View attachment 2604027
Here's what I would do. I'd buy new plugs plus one plug that's "hotter" than the others. That is to say the electrode is longer and runs hotter. I'd put a tiny amount of anti-seize on the threads and put in the new ones. If number one fouls again, I'd install the hotter plug. Number one is telling you a story. It is way different than the others and not in a good way. I wonder if the valve stem seal on number one intake is kerplooie.
 
#5 ·
Before you do all the other have suggested, run the engine as hot as it gets, spray some carby cleaner in the throat and make WOT at the same time until it chokes and dies. Leave it for a minute, rinse and repeat.

My 450 changed the tune significantly after I emptied 2 cans in the throat and it improved burn up.
It will not fix your problem but it may reduce it by a lot as the net gain is that the valve seats will be cleaner and close better.

Long time ago I had a Mazda that made 1 plug the same way. It was combination of big mileage (400t k's) and valve stems. It did consume oil about 0.5L/1000 km's but it went well.
Because it idled perfectly I presumed it must have been valve stems wear difference that made this plug foul. It would foul abit quicker if driven irregularly or short distances, but freeway run would make it last 10t k's.
 
#7 ·
It would be interesting to know if adhesive can be successful where two dissimilar metals heat and cool at different rates.
I successfully used yellow loctite on almost no interference bearing mount and it lasted well but temp change was minimal and it was very similar hardened steel materials.
Perhaps you can increase interference with roughening the surface in a pattern shape (sorry, not familiar with the term for this - in English)
 
#8 · (Edited)
I've been searching through the Loctite website looking for a suitable adhesive, not easy. I have primarily been looking for high temp bearing retainers, as I am sure the guides must get very hot, 620 is good for 200 degC.


My plan is to buy an new guide and an oversized guide and see which one fits best, light peening or knuling should help to retain if the glue fails.

I was searching through the new "EPC" to find the p/n for the valve guides but cant find them, anyone know what page they are on?
 
#9 ·
On my E320, I used a sealant/adhesive on the rocker/breather covers. Mercedes have a product for this, but I used an equivalent. It is good for 250C (300C max). Do you think that area would ever get that hot? The block doesn't get much over 100C.

Most of the sealants/adhesives are not rated for use with synthetic oils. But this one is :


Not saying this is right for your application, but it may be.

JB-WEld have a product called Extreme Heat - apparently good at very high temperatures!

Maybe you need something that is more liquid? Maybe this one?
 
#10 ·
Thanks for the suggestions, I had seen 2620 and considered that one but then discounted it as its a thread sealer rather than a sleeve sealer, but not being a mechanical engineer I'm not sure if it matters.

As for the temp, I have no idea but as its in contact with the valve, I guessed it must get pretty hot.

The new "epc" is a pain, it doesn't correlate part numbers to chassis numbers. Is there an old version available anywhere?

2604093
 
#13 ·
EPC shows same parts for all 044 450SLs with 982 engine. Does have some different sizes of guides. This may be the same as you already posted?
I am having trouble moving epc output from virtual machine. Will try and see what is wrong. For now, this is basically what it said for intake valve guides.

----- A 116 050 35 24 . VALVE GUIDE
. Replaced by: A 116 050 36 24
-
----- A 116 050 36 24 . VALVE GUIDE. INTAKE
. [067, 006] NO LONGER AVAILABLE,INSTAED 116 050 36 24
-
11 A 116 050 36 24 . VALVE GUIDE. INTAKE,REPAIR SIZE I
. [007] 14.043-050 MM

11 A 116 050 37 24 . VALVE GUIDE. Replaced by: A 116 050 49 24
. +001 A 110 053 02 58
-
11 A 116 050 49 24 . VALVE GUIDE. INTAKE;REPAIR SIZE II 14.20 MM
11 A 116 050 38 24 . VALVE GUIDE
. Replaced by: A 116 050 50 24
. +001 A 110 053 02 58
-
11 A 116 050 50 24 . VALVE GUIDE. INTAKE,REPAIR SIZE III 14.40 MM
 
#15 ·
#22 ·
Yes sorry, I typed 982 because that is what our earlier models have. But 985 didn't show up either for that 116 050 4724 part number.

Hmm, don't know what this means, could it be multiple tolerances with one part number?
Could it be that the diameters are not uniform along the length - tapered or stepped diameters??

In looking for a picture of the guide, I went to Autohaus Arizona (usually reliable). They also say that the 4724 part number doesn't fit a 1980 450SL ????? Maybe check with a Mercedes dealer along with engine number to be sure!
 
#24 · (Edited)
#25 ·
Found this company who appear to be a manufacturer of valve guides for OE markets.

Interesting description of how the valve stem heat is dissipated. Just thinking that having a layer of Loctite or similar may affect the heat transfer from the stems through the guides to the head.


How do guides become loose? Maybe if valve stems lose lubrication, they bind and cause some movement of the guides? Who knows, but interesting that MB originally had three sizes for our cars.
 
#27 ·
Yes, certainly less severe service on inlet. But there is still frictional heat to dissipate. The copper-zinc alloy that MB uses likely transfers heat better than cast iron does.

By the way, are the guides made to an exact fit? Or do they need honing or other machining during installation? It's been a long time, but I seem to recall something about that. Also first freezing guides before installing. Maybe have a good MB shop rebuild the head?

Anyway, good luck with it.
 
#29 ·
Thanks for that, I am now also understanding that there is also a slightly over sized version of the original part.

A 116 050 36 24 . VALVE GUIDE. INTAKE,REPAIR SIZE I. [007] 14.043-050 MM

and I have also found the dimensions for the A 116 050 4724 which is also 14.043mm, so this is equivalent to the first repair size as above.

I also found the dimensions fro the 3624 and the 4724 in the specs for the TRW equivalent parts.

1160503624 ---> TRW 81-2685 ----> 14.035mm
1160504724 ---> TRW 81-26118 ---> 14.043mm
 
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