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How do these plugs look? Any signs?

2K views 18 replies 10 participants last post by  tuttebenne 
#1 ·
I thought that I was burning oil because I was not leaving anything on the ground and its going through 1qt/1k miles, but after pulling the plugs, it doesn't seem like its burning does it?

How do they look in general? These Denso plugs have 21k on them.

 
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#5 ·
That's how it feels, but that was 8 years ago and 100k now!

I have a leak from the oil pan gasket but the engine cover has a little oil on it, but certainly not quarts-worth...
 
#3 ·
This is funny. My E320 which is leaking oil into coolant and on the ground, barely needs any topping-up between oil changes, half qt at most, over over five thousand miles. Perhaps, DEX VI is so efficient for the transmission to save oil.

If you are burning so much oil per 1000 miles, you must smell and see something in the exhaust, like those from stinky two-stroke engines. The oil could be leaked and sprayed along the road when the engine is running. You should still see signs of oil leak on the ground. If nothing on the ground, where does the oil go? Hopefully, not in the coolant.

Hope that you don't have to pull your gasket for the 10th time. The spark plugs appear normal to me, not fouled with excessive oil.

jftu105
 
#7 ·
I Don't Like What I See

Just change those out with Bosch plugs. The Denso's aren't sparking properly.

The 1st two are caked with deposits of some sort. The next four are fuel fouled. I don't think you are getting a "complete burn" on your fuel, or it's running rich.

I see no symptom of oil however. What kind of fuel are you burning? I'd scope the cylinders and see what all the other internals look like. :nerd
 
#9 · (Edited)
Just change those out with Bosch plugs. The Denso's aren't sparking properly.

The 1st two are caked with deposits of some sort. The next four are fuel fouled. I don't think you are getting a "complete burn" on your fuel, or it's running rich.

I see no symptom of oil however. What kind of fuel are you burning? I'd scope the cylinders and see what all the other internals look like. :nerd
So you don't think those deposits are oil then and more just incomplete combustion?

My fuel economy is ok I'm averaging about 21-22mpg per tank and always have historically.

Also is there even a source for non-resistor Bosch plugs anymore?
 
#8 ·
Looks like value seals and/or guides starting to go bad. You should see what mine looked like when my 260e was consuming 1qt every 600 miles! There was no oil on the ground and exhaust didn't smell that bad when engine was warmed up.

Symptoms of bad seals can be a puff of smoke on startup or upon WOT.
 
#10 ·
#11 ·
There is no problem at all using the Denso plugs. They meet MB spec and give you the beveled gasket less seat need. As I'm sure you know, the Bosch plugs have flat seats. As a test, you might try some NGK BP5 ES. Again, they meet all MB specs.

Getting 21-22 MPG out of a m103 powered wagon ain't to shabby....
 
#13 ·
On these old engines in a perfect running condition will there be carbon build-up on the top of the cylinders? I definitely think I am running rich as the pistons look pretty dark. I'm going to buy an inspection camera and see if I can take a closer look.
 
#17 ·
Take a look at this device. One of my kids got this for me for Christmas and its perfect for what you are trying to do by peering into the sparkplug hole.

https://www.amazon.com/SanSiDo-Mega...e=UTF8&qid=1484780251&sr=8-5&keywords=sansido

As for oil consumption, when my '88 was using a quart every 500 miles the plugs were wet. Yours are getting dark. One thing to bear in mind with valve guides is that they will perform no better than the difference between the valve stem and the diameter of the guide. In other words, if there is wear on the valve stem, inserting new valve guides does not make up for the wear that has taken place. Even though the guides are a softer material than the stems, the stems do wear. This shortens the amount of miles after a head refresh before oil begins being consumed again. New valves along with guides is the best way to go.
 
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