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Discussion Starter #1
I own a Mercedes W115 with it's original M115 motor, I have a strange problem just when I drive with a speed over 100 KM/H for more than 3 minutes I just go to find my original header "Manifold" glows red.
I'm facing this problem for a very long time I have fully repaired the engine and changed exhaust and still facing the same problem.
I can find nothing wrong in the car while driving it except this, but only one strange symptom the valves adjustment becomes very closed nearly about every month.
I have paid for more than 1500 $ to solve this problem and without any new, please I need to solve this problem and I can't find any logical cause for this problem.
 

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Hi!

This could possibly be caused by retarded ignition timing. When is the last time the ignition timing has been checked or adjusted?

Ignition timing values:



There are more distributor numbers listed, if your isn't in that table, let me know and I'll digg out the timing figures you need :)
 

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Discussion Starter #4
Thanks for reply, regarding the timing I have checked it more than once even I have changed the timing belt, and regarding the fuel, UI have tried three types of fuel with the same result "80, 90, 92", any other suggestions please:crybaby2:
 

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Discussion Starter #5
I can't understand the timing table I asked the mechanic to check it to me, would you please describe how to check it myself
 

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Not enough sealant for the gaskets
Fuel regulation is not set or need new fuel regulator
could be a blockage on the exhaust system

Has air craft or racing fuel ever been used on it? If so it can burn out your engine really hard and manifold could crack.
 

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Thanks for reply, regarding the timing I have checked it more than once even I have changed the timing belt, and regarding the fuel, UI have tried three types of fuel with the same result "80, 90, 92", any other suggestions please:crybaby2:
If it is a normal compression engine, it requires at least 95 octane. If you use lower octane fuel, the ignition timing should be adjusted.
 

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Discussion Starter #8
Regarding the fuel, I have already tried to use as I stated above more than a fuel type each with different Octane percentage but with the same result, can any one please tell me how to check my car timing Note: I have the M115 motor
And I would also want to know what is the fuel regulator is it the fuel pump or it is another thing.
 

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Regarding the fuel, I have already tried to use as I stated above more than a fuel type each with different Octane percentage but with the same result, can any one please tell me how to check my car timing Note: I have the M115 motor
And I would also want to know what is the fuel regulator is it the fuel pump or it is another thing.
The M115 engine was available as normal compression or low compression. What version do you have?
 

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I can't understand the timing table I asked the mechanic to check it to me, would you please describe how to check it myself
First you go check your engine number (on the block) 115.9## - and then you go check witch distributor is on your engine (number on the distributor body) - and then you know which ignition timing you need (under "ignition timing without vac advance @4500RPM").

Disconnect the vacuume pipe from the distributor and block the pipe. Spin the engine to 4500RPM and check timing according to the table.

The table will also tell you if you have a wrong distributor fitted with wrong advance curve... I guess it wouldn't be impossible that this might have happend in the past...

Forgott, dwell angle needs to be set at 48-53° :)

The rest of the table are guide values to check if the distributor advances correctly. It could very well be that the advance mechanism is blocked/rotten. Try to clean the distributor and get the internals working.

A M115 is carburettor fed, there's no such thing as a fuel regulator like on a K-Jet. And he says the carb setup is good and checked. The mechanical fuel pump can't (or shouldn't) overcome the resistance of the float valve. And if it did, the car would be runing way too rich and rather die due to fouled plugs.

That said; what colour do the spark plugs have directely after the glowing manifold occured?
 

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Discussion Starter #13
Nothing can help from the above, please help me I'm facing a serious problem:mad::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2::crybaby2:
 

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if it was ever rebuilt make sure it has correct cam/rocker arms (taplets)
 

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Discussion Starter #16
dears, nthg can help from all the above and still I'm facing the same problem every thing seams to be ok but the same problem exists only one thing that show that it is effected "the valve adjustment after few days become again unadjusted and need to be adjusted once more"
 

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If it is running too hot, it makes sense that the valves will go out of adjustment.

Is the engine coolant at the normal temperature when the exhaust glows red?

Have you done a general research on the internet about this problem?

Did you check for vacuum leaks?

I still think that it is running lean.

I am not familiar with this engine but from what I have seen on line it has a side draft Stromberg Carburetor. These are known to be difficult to adjust properly.

The first thing to check is that it has oil in the dash pot.

Check to see if the piston moves freely. It should move up with some resistance and fall slowly.
 

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Discussion Starter #18
If it is running too hot, it makes sense that the valves will go out of adjustment.

Is the engine coolant at the normal temperature when the exhaust glows red?

Have you done a general research on the internet about this problem?

Did you check for vacuum leaks?

I still think that it is running lean.

I am not familiar with this engine but from what I have seen on line it has a side draft Stromberg Carburetor. These are known to be difficult to adjust properly.

The first thing to check is that it has oil in the dash pot.

Check to see if the piston moves freely. It should move up with some resistance and fall slowly.
Dear, thanks for ur reply
Yes the engine coolant is in normal temp, I have already searched for similar problem but with no benefit, I dont how if I can understand vacuum leak right but I think that it leaks because I have a problem in the central lock system and it doesn't work, I have double checked that the engine is not running lean with a mechanic.
Do you think that this problem maybe caused because of something that is damaged in the carburetor it self?
 

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Every time I see this post it just screams out ignition timing.

Since you haven't said anything about a knock or backfiring, it would seem that things are (mostly) fine at low RPM/idle (from your descriptions).

You have mentioned that there may be a vacuum leak or lack/loss of vacuum.

Finally there's the glowing exhaust manifold after operation at higher RPMs. This seems to pretty clearly indicate the escape of combustion into the exhaust system.

Putting all of these together points straight to late ignition at high RPM: ie; the distributor is not advancing ignition timing (likely because of insufficient vacuum) and combustion is occurring late in the power stroke. As a result combustion isn't complete by the time the exhaust valve opens and burning fuel escapes into the exhaust.

You had previously dismissed timing concerns by stating "nothing can help from the above," but you didn't say if the timing had actually been checked. If the vacuum advance mechanism of the distributor is not functioning properly, this situation may arise.

Your first order of business here should be to fully verify proper operation of the distributor, especially the advance mechanism.
 
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