C350 w204 coolant issues

[L John]

Going to do waterpump and stat to be on safe side new cap ordered cars just done 1000miles to london and back think if was head gasket would have given up on motorway surly Head gasket falure at 66.000 on a merc is very unlikely i hope

If it's overheating it's not a good idea to keep driving it. If it's not overheating but it is the head gasket causing air to escape from the cylinder into the water system it would be a bad idea to keep driving it.
If the problem is blockage or poor water flow it would be a bad idea to keep driving it.
If more damage occurs from keeping driving it, please don't say this shouldn't happen to a Mercedes.

 

[Steve@Avantgarde]

I keep saying this on every thread at the moment because the approach seems to be "well i will throw this bit at it in the hope it will cure it".

Guessing at what might be wrong is not diagnosis. Start with the flow check, it will cost you nothing and will enable you to move on to the next part of the puzzle if it turns out to be ok. What's the point of replacing the water pump if there is a blockage somewhere or the head gasket has gone?

F-D-C

Fault - Diagnosis - Cure

 

[star]

I keep saying this on every thread at the moment because the approach seems to be "well i will throw this bit at it in the hope it will cure it".

Guessing at what might be wrong is not diagnosis. Start with the flow check, it will cost you nothing and will enable you to move on to the next part of the puzzle if it turns out to be ok. What's the point of replacing the water pump if there is a blockage somewhere or the head gasket has gone?

F-D-C

Fault - Diagnosis - Cure

My thoughts exactly. It seems some would rather spend/guess on fitting parts than spending a little on a proper diagnosis and then replacing the parts required.

 

[M1ckc350]

Considering waterpumps are a know falure on these engines its more than likely the problem if was head gasket causing stystem presure car would have given up on an 1000mile trip.will look into it this weekend and diagnose Properly was just on ofchance someone else had same issue
Many thanks for all usfull info and tips

 

[M1ckc350]

If it's overheating it's not a good idea to keep driving it. If it's not overheating but it is the head gasket causing air to escape from the cylinder into the water system it would be a bad idea to keep driving it.
If the problem is blockage or poor water flow it would be a bad idea to keep driving it.
If more damage occurs from keeping driving it, please don't say this shouldn't happen to a Mercedes.

Should not happen to a any mercedes with such low miles others failing at 30k it seems mercedes have know problem with waterpumps on these engines and offer 50% to cost of repair.

 

[L John]

Considering waterpumps are a know falure on these engines its more than likely the problem if was head gasket causing stystem presure car would have given up on an 1000mile trip.will look into it this weekend and diagnose Properly was just on ofchance someone else had same issue
Many thanks for all usfull info and tips

There's a helluva lot more pressure in the piston than in the water system. With a leaky head gasket pressure can bleed to the water system but is unlikely to let water into the piston until it gets worse.
On a petrol it would begin to lose a spark with water ingress, on a diesel it will happily run until you get hydraulic lock.
The pump is looking less likely with a 1000 mile trip, assuming it was running at normal temperature.
You are a brave man to keep running it either way.
One careful owner?

 

[star]

Considering waterpumps are a know falure on these engines its more than likely the problem if was head gasket causing stystem presure car would have given up on an 1000mile trip.will look into it this weekend and diagnose Properly was just on ofchance someone else had same issue
Many thanks for all usfull info and tips

Anything can fail at anytime. Water pumps do fail BUT it's not a common one on this engine, maybe a 651 and then it just leaks. If it wasn't pumping, it would overheat and then pressurise.

 

[Steve@Avantgarde]

Considering waterpumps are a know falure on these engines its more than likely the problem if was head gasket causing stystem presure car would have given up on an 1000mile trip.will look into it this weekend and diagnose Properly was just on ofchance someone else had same issue
Many thanks for all usfull info and tips

I have worked on mercs for the last 16 years or so and I have only ever replaced 3 water pumps on the 642 engine. I do 3 a week on the 651 though.

It depends which way the head gasket has blown, it is entirely possible for it to fail and not cause you any problems until it has to idle in traffic. That said, you dont know it doesn't have a blockage somewhere causing your problems...

 

[M1ckc350]

There's a helluva lot more pressure in the piston than in the water system. With a leaky head gasket pressure can bleed to the water system but is unlikely to let water into the piston until it gets worse.
On a petrol it would begin to lose a spark with water ingress, on a diesel it will happily run until you get hydraulic lock.
The pump is looking less likely with a 1000 mile trip, assuming it was running at normal temperature.
You are a brave man to keep running it either way.
One careful owner?

Cars not being used untill rectified Running temp was 90d on full trip which seems to been normall will do sniff test over weekend to see if any head gasket issuee

 

[M1ckc350]

I have worked on mercs for the last 16 years or so and I have only ever replaced 3 water pumps on the 642 engine. I do 3 a week on the 651 though.

It depends which way the head gasket has blown, it is entirely possible for it to fail and not cause you any problems until it has to idle in traffic. That said, you dont know it doesn't have a blockage somewhere causing your problems...

Thanks for info steve will do sniff test over weekend and investigate futher

 

[Johnny d]

Thanks for info steve will do sniff test over weekend and investigate futher

Hi did you get this sorted? I’ve got the same issue

 

[stumo]

Another easy test you can do to rule in/out head gasket is to check if there is pressure when stone cold after it has sat overnight after a decent run. If you remove the cap and get a burst of pressure, then it is highly likely the head gasket. If it was just pressure from heating, then once cooled off it shouldn't still have that pressure.

 

[Mike1*1*]

Hi,

Did you problem get resolved, I have exactly the same issue and driving me insane. Thanks.

 

[JBell]

Hi,

Did you problem get resolved, I have exactly the same issue and driving me insane. Thanks.

Yours is a different engine

 

[D5meister]

My guess is airlock post rad swap.