A-Class mayonnaise

Helmet Vonthrob

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My partner's A-Class (1999 - 160 Elegance has always suffered an amount of mayonnaise in the filler neck, I usually clean it up at every oil change but it comes back to a lesser or greater extent.

I am using a reasonable semi-synthetic oil and change it regularly, my partner does 80 miles/day 60 of which is motorway (and she doesn't hang about) so it's not like she does a 2 minute school run twice a day.

Are there any known breather issues or anything issues that could cause this??
 

bi-turbo

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Not that Im aware of I think it's just due to the length of the oil filler neck, allowing the "yeast" to gather there
 

television

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If you are loosing no water then just leave it,if the water is going down a little then a bottle of K seal may work wonders
 

5pares

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Its normal for an a class,nothing you can do.
 

television

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Eat more salads,,good for you :D:D
 
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Helmet Vonthrob

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So the A-Class appears to be losing water, it looks like it is coming out the overflow but there doesn't appear to be any sign of headgasket failure in terms of overheating (although how you tell with no temp. gauge I'm not sure).

I guess the next stage is a new expansion cap.

Are these a common failure point?
 
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Helmet Vonthrob

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So the A-Class appears to be losing water, it looks like it is coming out the overflow but there doesn't appear to be any sign of headgasket failure in terms of overheating (although how you tell with no temp. gauge I'm not sure).

I guess the next stage is a new expansion cap.

Are these a common failure point?

And does the thermostat stick closed?
 
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Helmet Vonthrob

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Does anyone have a thermostat replacement guide??
 

jibcl500

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Does anyone have a thermostat replacement guide??

Is the cooling system getting pressurised?

IS the oil level increasing?

How does the car run?

As the air temp gets cooler the A class all have a build up of mayo in the filler neck in the summer months it doesnt, if the cars only does very short drives to and from work then that wont help, a good drive is needed.
Alos find a local indie and have them take a look.

jib
 
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Helmet Vonthrob

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Is the cooling system getting pressurised? - yes

IS the oil level increasing? - no

How does the car run? - fine

As I said before, my partner does 80 miles per day (60 on the motorway) so the engine is getting up to temp.

That's why I suspected the thermostat!

But I "think" there is a bit more mayo so I wonder if the t.stat is jammed 1/2 way open.

I had a go today at the job and have worked out that I need a couple of extra thumbs to be able to do the job. I just can't work out how to get round the steering column, this would be easier on a LHD (but still a pain as there is limited room!)
 

turbopete

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thermostat? steering column? these are nowhere near each other on ANY car!
 
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Helmet Vonthrob

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thermostat? steering column? these are nowhere near each other on ANY car!

WRONG! - you obviously haven't looked at an A-Class (transverse, canted engine, designed for LHD then "converted" to RHD).

The steering column takes a big left turn after the bulkhead, across the back of the engine (just in front of the thermostat housing!!) and into the rack.
 

dbanbery

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if its losing water through the overflow the chances are its got a leak on the head gasket that is pressurising the coolant circuit.
 
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Helmet Vonthrob

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if its losing water through the overflow the chances are its got a leak on the head gasket that is pressurising the coolant circuit.

Although talking to people in the know, A-Class head gasket failure is (almost) unheard of.
 

dbanbery

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yes but at the end of the day you dont have to be mixing oil and water for the head gasket to be going. it all depends where the head gasket starts to leak. water in oil = mayo, but in your car this may be unconnected. if the cooling system is getting pressurised its pretty much a no brainer that its the head gasket, as the cylinder head is the only place where pressure can build up. i dont think the thermostat has much to do with it as if the stat was stuck 1/2 open it wouldnt pressurise the system, it just wouldnt swirl in the coolant bottle as well, and it would probably run slightly hot.

i'm not very familiar with the layout of A Class's, but regardless to it being undeard of, it is possible for the head gasket to go on any piston engined car that has one. its not going to blow up tomorrow but i would get it looked at a bit more in depth with a view to it being the case.

whether or not you think i'm in the know is another question ;)
 

turbopete

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WRONG! - you obviously haven't looked at an A-Class (transverse, canted engine, designed for LHD then "converted" to RHD).

The steering column takes a big left turn after the bulkhead, across the back of the engine (just in front of the thermostat housing!!) and into the rack.

i stand corrected. any front wheel drive vehicles ive worked on (almost everything non MB) had the thermostat nearest the radiator, between the cylinder head and the radiator top hose, nowhere near the steering column or the bulkhead, hence my saying they are nowhere near each other! i must try to have a look at an a class, next time i get the opportunity!
 
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