Thanks for looking that up
Might be a
US spec as the 83 500 SEC was not offered in US.

I guess its ok as its on it & they say its interchangable.

Congrats on your new tank
but that hose is scary...

After viewing the photos of your hoses, I believe your problem is a bad head gasket. I just went through the same problem last week. I replaced my head gasket because oil got in the coolant and head pressure blew out the bypass hose. Not a fun job, but it had to be done. I also replaced all of the rubber hoses due to oil contamination and swelling.

__________________

1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Thank you for your imput but that's not my situation this time. That happened to me too but about 2 years ago. I replaced head gasket, oil cooler, all hoses, exp tank, thermostat, pressure cap, etc. That was a pain. This time, coolant and oil are clean. No mayo in the system and no coolant loose. I'm sure head gasket is good now.

__________________
-----------------
Juan
1995 E320 Sedan
2008 Ford Escape
RC Helicopter

I hope you're right Juan, but you do need to change those swelled hoses. I can't imagine how those got that way if you replaced them recently.
Good luck with your new tank.

Dave

__________________

1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

There's no way that the hoses got like that from anything normal. If the cap is doing its job it would relieve the pressure from typical expansion before the hoses and tank would fail. If the engine is putting out so much pressure due to a failed headgasket or crack in the block or head that it cannot handle it, then this would be the result. The latter is what I suspect, despite your feelings that all is well. I would bet your engine is facing major work in the not too distant future, unfortunately. If I were you I would have the coolant tested for hydrocarbons, that would tell you conclusively you are facing a leak from combustion into it. You don't always get oil in the coolant from a leak like this, but the overpressure is a sure sign of it.

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Is it possible he has a combustion gas leak at the head gasket????? higher pressure than oil leak?????????????? jim

__________________
James A. Harris

I really appreciate your imputs and hope you keep posting about this. I feel scared now

This is my first benz and it only has 50k miles. I have invested A LOT of money in it during the last 2 years, including head gasket, all components in the cooling system, head check, etc. I understand you can expect more than 200k miles from an M104 engine and I feel very dispointed if your diagnostic is right. I hope you are wrong bacause if you're not, I think I will just need to sell the car. I can't afford the mainenece cost if that keeps that way.

Just for the record, this is what I have replaced during the last 2 years (and remember it is 50k miles):

Wiring harness.
ECU (inyection computer)
Throthle body
2 Coils
Radiator.
Every hose in the cooling system.
Water pump.
Oil cooler.
Thermostat and pressure cap.
Expansion tank (twice).
Transmission overhaul.
Head gasket (head has checked for cracks / wrap).
Valve cover gaskets (leaking thru sparks holes).


Thank you guys and please keep posting. I need to be sure about this to make a decision about the car.

I think next step will be getting a new upper hose and see if the overpressure situation comes back. BTW, lower hose and bypass hose are same age but don't get inflated, if that means something for the overpressure diagnostics.

Thanks

__________________
-----------------
Juan
1995 E320 Sedan
2008 Ford Escape
RC Helicopter

Those are a lot of new parts for only 50K miles. You stated that the head was checked for cracks/warp, but was it resurfaced before the head gasket was replaced? And, did a machine shop do the checking, or was a straight edge used? Was there any deep pitting on the surface of the block?
Have you performed a compression test? Keep in mind that you are also subjecting the new radiator to the higher than normal pressures.





Keep us posted on how the new hose and tank work out.

Good luck,

Dave

__________________

1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Does that hose stay hard like that overnight or is it soft again? Now that you have replaced the tank you should be able to see if the pressure is coming from heat or exhaust leaking into the cooling system. Start the car if the hose is soft and feel it as soon as it starts...if it starts to get hard almost immediately that is surely a sign of trouble. It should take a minute or so for the cooling system to heat to the point where the hoses start to get hard...if they get hard within the first few seconds you surely have a problem...

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Hi,

The head gasket was replaced by a BMW / Mercedes independent shop. They sent the head to a machineshop to be tested and said everything was good. The block looked really good. The head was removed because oil was in coolant but since the head and gasket were so good when they removed the head, they keept looking and discovered that coolant contamination was caused by a bad oil cooler and that's why that was replaced too. No compression test yet.

The hose gets soft when the engine cools down overnight. I like your idea about testing the hose hardness while the engine warms up. I'll try that this weekend and will let you know.

That hose was replaced because the oil contamination in the system got made almost every hose fail and got leaks everywhere. Maybe there was still some oil when I replaced that hose and oil atacked it too? If you see the old tank in the picture, it has a strange color too and maybe that mayo made it fail? Just another theory praying for a cheap fix...

Thanks again.

__________________
-----------------
Juan
1995 E320 Sedan
2008 Ford Escape
RC Helicopter

Good Luck
You've had a long hard road
Hope you get that solved without too much more $

__________________


83 500 SEC Euro 198K

I didn't think they made an oil cooler that was integral to the radiator...any car I'd seen with an oil cooler used an air-cooler, like its own free standing radiator...now the tranny coolers are integral to the radiator but the oil cooler?

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

My car is the Euro version, built in Germany and some things can be different from the USA version. My motor number is 104992 12 076120 and it has an oil cooler integrated in the filter housing. Is also known as the oil heat exchanger. Item 53 on the attached diagram. That thing was leaking and needed to be replaced.

Attached Thumbnails

 

__________________
-----------------
Juan
1995 E320 Sedan
2008 Ford Escape
RC Helicopter

Hi,

This is driving me crazy.

With the engine cool in the morning, the hose is soft and after starting the engine it takes a long time to get hard (about 5 minutes I guess). It keeps soft while the hose is cool. After the stat opens, the hose get's hard and it takes a long time to get inflated. That's good news because I still think it is not related with the head gasket or combustion gases.

But, there are also bad news. The new tank (2 weeks old?) is already starting to show some small cracks on top. I'll try to post pictures tomorrow.


And more bad news. Today I got a new coolant leak. There were no leaks until today but this morning I opened the hood (as I do every day) and the coolant level was about 1/4" inch low. I added some coolant (about 300 cc) and started the engine. I was doing the hose test, so I let the engine running for about 10 minutes. After that, I realized there was coolant on the garage floor. I looked under the car and I saw coolant dropping from some place close to the transmission.

I was late for job, and I could't find the leak source but I think it is a strange place for a coolant leak. Transmission fluid looks good and radiator is new and overflow tank is not close to that point.

I think that overpressure did some damage. Maybe the coolant line to the oil cooler or something related to the heating system. Or maybe since I was pressing the upper radiator hose..... I don't know but this is so frustraiting.

I'll keep you posted and will really appreciate your imputs.

Thanks,

Juan.

__________________
-----------------
Juan
1995 E320 Sedan
2008 Ford Escape
RC Helicopter

If the new tank is starting to show some cracks, then I would perform a pressure test to see how much pressure actually building up in the cooling system. If it's over what the pressure range would be, then I would suspect head pressure.

Also, I would be concerned about other components getting too much pressure...radiator, heater core, heater valve, and all related hoses and clamps.

That's just my opinion.

I do wish you luck in finding the problem.

Dave

__________________

1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible