A few weeks ago I flushed the coolant in my 1991 190E 2.6, refilled and
ran the car for approx 500 miles with no problems. The other night my
wife mentioned that the radiator light had come on intermittently will
driving home, so I checked the coolant reservoir bottle, and sure enough
the coolant level was down to the sensor. I refilled and she drove the
car another 50 miles -- I checked again and found that the coolant level
was down about 1 inch in the coolant reservoir.
I checked all of the hoses, radiator, thermostat etc., (some of you may
recall that this car had had a head gasket replacement in March of last
year - see: http://tinyurl.com/gu8z ) and still could not find a leak. I
finally noticed coolant leaking under the car on the drivers side and
appeared to be dripping from the engine block, bell housing area.
I have eventually located the general area of the leak; it appears to be
coming from the oil filter housing - the unit that the oil filter is
mounted on and connects into the block. I can find no leaking or wet
area above the unit, but definitely coolant just below the unit (it
pools on the block lip just beneath the unit, and then produces the
drip/leak mentioned above). No oil dripping from the unit, no oil in
coolant, no coolant in oil, no hose leaks that I can find, car is
running fine, temps are between 80 - 90c under summer driving
conditions, just this new & very prominent coolant leak.
So, before I attempt exploring further my questions are:
1. Anyone else heard of coolant leaks from this unit/area?
2. Is there an O-ring or gasket that could have broken down & I can
replace? I'd hate to spend $$$ having a simple $2-3 gasket replaced if
this is the case.
Any suggestions/advise appreciated.
Thanks Bill, the heater pipe & hose (the one leading from the head above
the unit into the driver side firewall) looks fine on the exterior.
Without taking too much apart, I was able to get my fingers into the
area around the top of the oil filter housing unit and didn't notice any
oil, coolant, or anything wet above the unit -- only the pool directly
below the unit. I'll take the airfilter housing etc., off tomorrow and
see if I can find anything obvious. Would a faulty o-ring seal in the
heater pipe display similar symptoms?
Sure. A trickle of water follows the easiest path to the ground, and is hard to
425 White Horse Pike
I experimented a bit this morning -- I topped off the coolant, turned
off all heat/cooling and drove my son to work, round trip 50 miles,
using only the standard air vents for air circulation. No coolant loss,
no drips, no wet spots under the filter housing. I plan to let the
engine cool down and then do some more checking this morning -- I'll
start the car, bring it to normal operating temp and then turn the
heater & cooling on... I suspect that the drip/leak will re-occur after
I've done this. In the meantime I'll do some research on how to replace
the heater pipe o-ring :-)
Just an update -- I found the problem. The problem was right where you
suspected, fortunately it wasn't the o-ring or the connector pipe
leading into the head, but instead is a bad hose to the heater pipe at
The reason that I didn't detect any wetness at this connector yesterday
is I checked that area when the engine was hot and had been turned off
for several minutes. The engine heat was probably dissapating the
coolant rapidly on that part of the engine. So, every time I turned the
car off, waited a bit to check around the head heater pipe etc., that
coolant had evaporated and I was only able to find the left over puddle
that formed around the base of the oil filter unit and below.
The hose was cracked where it connects to the head heater pipe, so I cut
about an inch off and re-attached. That cracked & split, so I cut a bit
more off -- same result. Note: I hadn't intended to leave the old hose
on, just figured that I'd get it working long enough to get to the parts
Anyway, got the hose off and will replace with a new one from MBZ
tomorrow ($30.49 including tax). I figure that it'll be $30 well spent
rather than trying to jury rig an after market hose from Kragens &
wouldn't like to think of the mess if the hose had cracked on the
drivers compartment side of the firewall.
Thanks again for your help & kind advise!
For others that may have a similar problem in the future; the heater
hose on my 1991 190E 2.6 is MBZ part #201 832 0594 and is the hose that
connects from the rear of the head through the firewall on the drivers
side to the heater unit. Getting to the hose in the engine compartment
is a snap, and getting to the other end behind the firewall was pretty
easy as well. All you need to do is remove the plastic leaf guard tray
(don't know if this is the correct term) that covers the area between
the windshield/wiper assy and engine compartment firewall, undo the
clamp on the other end & slide the hose out of the firewall hole. There
is enough room on the drivers side of the firewall (from the top) to
undo & redo the hose and clamp, so no need to attempt taking off the
firewall panel itself. Caution - be sure to drain the coolant from the
engine/radiator/coolant reserve bottle first!
All in all about 15 minutes to get the leaf guard tray off and remove
the hose. Hopefully about the same to replace it, and an hour or so to
refill & test.
Symptoms for my problem:
- Loss of coolant - primarily when the heater or cooler is used
- Coolant drips underneath the driver side of the car
- Coolant puddle at the base of the oil filter unit that connects to
(you can see this with a flashlight by looking at the bock just in
the oil filter assembly -- I saw a small puddle, twisted a paper
a stick, and was able poke it down into the area to dab up the
liquid & confirm
that it was coolant and not oil).
- The car didn't have any major coolant drips or major loss of coolant
while driving with the heater and/or cooling system off.
- The only way that I found the leak was to start with a cool engine,
start the car and let it run for approx 5 minutes with the heater on
high, then shut the car down and check for dampness/leaks around the
heater pipe & hose that connects to the engine head. That brought the
car up to temp, opened the thermostat, and yet kept the head etc cool
enough that I could detect the wetness with a paper towel and not burn
my hands in the process.
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