W212 small coolant loss advice

[theclass]

Hi All

I have a 61 plate W212 E250 purchased as an approved used, I've had it for nearly 12 months without issue, a couple of weeks ago however I got a coolant warning light come on, took it into the dealer who topped it up, they were too busy to do any further checks.

I then took it into Wayne Gates (my trusted indy!) who did a pressure test (screwed some sort of guage onto the expansion tank and pumped), all was ok, they also checked the common locations for leaks including the waterpump area and all was ok.

I also took the oil cap off and could not see any mayo.

My concern is, I've been checking the expansion tank regularly and it does look like the level is dropping, have not got the light yet but I expect I will soon, any other ideas as to what might be going on? its typical that my tier 1 warranty has just expired, I'm hoping the fix will not be too expensive, car has 50-60k on it.

Thanks

 

[Monkeylegend]

I had similar with mine, low coolant light came on. I took it to Mercedes who had it all day, did a pressure test, checked all the gaskets but couldn't find a leak.

Had it back about 3 days and it came on again and I could hear a slight rumbling noise. Turned out the water pump had a slight leak that was not picked up on the pressure test, but worsened over further use.

I think the water pumps are plastic and a known issue, although mine had done just over 200k before it needed replacing. Not excessively expensive, under £400 but thankfully Mercedes (Robinsons) replaced as a goodwill gesture because they hadn't identified the leak when they had the car in.

 

[theclass]

Thanks for the reply, sounds like I'll just have to see how it goes, good news about your dealer, mine tries to charge me even for stuff covered under warranty

 

[T5R+]

If not the water pump or hose then there is a part that sits between engine and bulkhead that is the culprit.

You may notice that at high and sustained motorway speeds that the coolant falls but at sedate use hardly moves.

 

[Braincrank]

Like T5R+ said, it could also be the heater matrix that sits inside the car behind the dashboard . I had that issue.
It was loosing coolant when I switched the heating on and made a gurgling sound.
It's a pig to get to and I gave up after taking most of the car apart. I then used Kseal instead and that sorted it .

 

[Braincrank]

Also , check the filler cap.
I had a faulty one a few years ago , it won't show up when you do a pressure test because you take the cap off to fit the pump and gauge on ....

 

[MercE350]

I had the same MY of E 350, I had same issue right at the start, took it back they checked it, put on post here asking the same, I found out that the sensor is sensitive and the level has to be right on or just above where the black plastic meets the white plastic of the bottle, hope this makes sense, if you remove the cap you will see what I mean

 

[jaymanek]

On that engine the leak will be either water pump, fuel filter housing, egr cooler seal or radiator. Possibly more than just one of those!

Very common for leaking. Water pump must be changed complete with housing. MB now do exchange items which are a lot cheaper than they used to be. Fuel filter housings are the next most common cause.

Also hose clips are problematic. We replace for proper old style hose clamps.

 

[theclass]

Thank you for the replies, feel a bit more reassured as have more info now.

Not had the light again but I can see the level has dropped ever so slightly below the black bar, can see a bit of white.

I did think of the radiator cap but theres no marks, thought there may be telltale signs if its leaking from there..braincrank did you have any visual signs RE your cap?

 

[ph47mf]

sorry to revive and hijack this old thread, in case new threads on the same subject annoy mods

The coolant warning light came on when i started the car 2 days ago (it hasn't come on since), I checked the level but i can't make out whether it's full or not, there is no marking or wording to say full or empty, i read the manual but the instruction picture is so small it hasn't made me any wiser, can you guys tell from the pictures?

if it does need topping up, what kind of coolant do i need for this W212 facelift?

 

[derektrotter]

I'm afraid your pictures do not seem to be working.

 

[clk320x]

sorry to revive and hijack this old thread, in case new threads on the same subject annoy mods

The coolant warning light came on when i started the car 2 days ago (it hasn't come on since), I checked the level but i can't make out whether it's full or not, there is no marking or wording to say full or empty, i read the manual but the instruction picture is so small it hasn't made me any wiser, can you guys tell from the pictures?

if it does need topping up, what kind of coolant do i need for this W212 facelift? :dk

will say in yours owners manual

or ring up your local MB and state Reg and that you want to buy some coolant concentrate... I only use the genuine stuff

 

[ph47mf]

Well at the time I didn't have time to go to Merc so I put some water in. 5 months later to yesterday, the coolant warning light came on again and on inspection, the level has gone back to pretty much the same as what's on the picture, so I bought some Comma G48 from Halfords at £18 , let's see whether the level stays.

Does your car eat coolant? I wonder if there is a leak somewhere but 5 months to get back to the same level is not too bad?

 

[Deleted member 131833]

Could it be you are overfilling? Overflow will spit it out on expansion, level drops, light comes on, you add more water and so on.

My cars water level drops to the same place then does not drop further, I too kept filling it up then decided that it never dropped below a certain point.

 

[ph47mf]

Maybe, because i never got a definitive answer from anyone, even the manual, to say where the 'full' mark is. I was advised to fill it to just where the black plastic is.

However if it spits out the excess and return to the normal level, the warning light shouldn't come on? it comes on only when it's low?

Well 2 days and tank is still at the same level and no blue stuff under the car, so far as good.

 

[Ash]

Maybe, because i never got a definitive answer from anyone, even the manual, to say where the 'full' mark is. I was advised to fill it to just where the black plastic is.

However if it spits out the excess and return to the normal level, the warning light shouldn't come on? it comes on only when it's low?

Well 2 days and tank is still at the same level and no blue stuff under the car, so far as good.

I'm pretty sure the manual says to fill up to a couple of cms below the neck of the expansion tank. I had a 2011 212, the level looked low, the temp gauge went up, the fan went on. In the end i had to spend a lot getting the pump replaced etc. Not before topping it up a couple of times. After that the temp gauge always read a little high. Car has now been sold

 

[JPGOLF]

I have a 2010 S212 e class estate that is losing water. 1/2 ltd per mile. I have changed the water pump,and had the fuel filter hosing off and was in good order. At the rate I am losing water I would have seen a spray somewhere on the engine or rad, but nothing. Any help would be good.

 

[AW8]

It needs pressure testing...although odd no visible leaks detected when losing 1/2 litrr per mile. I am assuming the oil and coolant don't seem to be mixing & you have removed cover & tray before inspecting & when engine temp normal.

 

[kendog91]

I had a similar issue, was found to be the water pump, if you're a tools on the drive guy, this would take you around 30 to 40 minutes to change yourself. There is another known isuue to be the fuel filter housing, I would check them both.

 

[steveq]

I suggest that you check for leaks when the engine is running but cold.
I only found my water pump was leaking by looking at it when the engine was cold. When the car was up to temp the coolant evaporated immediately.
Did you replace the water pump with a genuine MB one?

You could try putting dye into the coolant.