My 91 190E 2.3 keeps losing coolant. The idiot light comes on after I drive 20-25 miles. Just had a radiator, fan clutch and T-stat installed, but problem still exists. Great site! Thanks for the help.

Is there any coolant on the ground after it reaches operating temp? Hoses, expansion tank, pressure cap, water pump weep holes?

If no external leak, do you have a cloud of very white exhaust following you for those 20-25 miles?

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Sounds like head gasket time(assuming no external leaks).

Air in the system?
MarkC

Air in the system would cause a hotter operating vehicle and I suppose that could cause some sort of boil over which should be obvious.

I wouldn't jump to pull the head until I had pressure tested the cooling system. You don't necessarily need dye to do this test.

Auto Zone and other mass-marketer parts house will rent you a cooling system pressure tester for about the cost of a new one. Usually around $75.00. The test is performed on a cool engine.If you have an encapsulation pan underneath, remove it first. There are usually anywhere from 4 to 8 small bolts holding the pan on. In many cases, an 8mm socket gets them off. If you leave the pan on, you may not see where the drippage is coming from once the system is pressurized.

I pump up my system to about 17 lbs. I have a 20 lb. cap. Automotive theory manuals indicate that if you pump up too much, the water pump seal may be damaged, hence I back off a bit. Once the pressure is on, you start looking for leaks. You can bet that if it's external, you'll soon see drippage on the ground underneath the car. You then know where to start looking.

Benzmac once commented that this test is a good way to know just how tight to get the hoses snugged down. I use this approach whenever I change hoses to help avoid breaking the plastic upper neck on the radiator.

If you see no leakage after 5-10 mins of being under pressure, then it's possible you have a leaking head gasket and the test for that is a whole 'nuther story.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

No, there is no white smoke when the car is driven. It sounds like air in the system, because the car does tend to start running hot. How do you get the air out. I finally found a service manual for the car, but it won't be here until Friday or Saturday. I think I'll have the pressure test done. It seems like the prudent thing to do. Just one question. What the heck is a belly pan, and where is it located?!?

Encapsulation shroud or pan or belly pan is a large piece of plastic that covers the underside of the vehicle from about where the radiator begins on back about 3 ft. or so.

Use the SEARCH facility for air bleeding techniques. In one post it was suggested to elevate the front of the car slightly, remove the coolant cap; then start car and watch for air being expelled from the coolant expansion tank. Some simply remove the coolant cap and start the car.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Bleeding is a good idea but, 201 heater cores and veater control valves will leak as well. The heater core is tough to see but, the heater control valve isn't bad, just apply pressure and look through the r/h cowl cover.

Test that cap as well, I've seen some lose coolant for no reason only to find a dead pressure cap.



Joe

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Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.
Raleigh NC
919-881-0364

jack front of car or put on ramps will force fluid to rear and air to front then add fluid to system works well.

look at the new t-stat those gaskets can be leaky at times or if the mechanic is an ******* he may have used silicone gasket maker instead of a real gasket (this happened to my dad once) the silicone stuff in my oppinion isnt really a gasket maker as much as it is a gasket seal helper, by smearing a light coating of the stuff on gaskets it helps fill in nicks and voids that the gasket may not be able to but you cant torque the item down on the gasket for a few hours as that will squeeze all the silicone out rather then letting it set up enough to form a good seal in conjunction with the gasket and part. I have used the gasket maker however to make sealing surfaces but those were not pressure bearing surfaces, in the case of my windsheild washer pump leaking at the reservoir because I wiggled it when installing clear front turn siginals and cracked the 18 yr old rubber gasket that had been just fine till I got to it amd messed things up

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1984
190e 2.3L
107000 miles

I guess the mechanic is an *******, because I can see blue sealant at the thermostat housing. Should I get rid of the sealant and install a real gasket?

Had the car running last night, and noticed steam???? coming out of the exhaust. After about 15 minutes there was a wet spot on the ground where the exhaust was hitting it. It was around 55 degrees F. when this happened. It smelled just like water. (no coolant smell) Any ideas??

that steam and puddle under the tail pipe is completely normal and results from the combustion of the fuel and the water in the air, the wetness would actually be pure water if not for the exhaust gasses mixing with it

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1984
190e 2.3L
107000 miles

Id install a real gasket they arent overly expensive and are definately better than the blue rtV sealant im assuming he used, dont get me wrong that sealant stuff is great just not as a gasket itself. if its assisting the gasket even better

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1984
190e 2.3L
107000 miles