I have an '89 190e, 2.6 that has developed a small coolant leak. Most mornings I find a small puddle of coolant beneath the car. The leak is far back, and seems to be originating somewhere near or behind the firewall. I suspect the heater core. Has anyone got any advice regarding how to find or test for leakage in the core?

Also has anyone had experience using the stop-leak products on the market? I think I might try disconnecting the heater hoses from the engine; flush the heater core and run some stop-leak through the heater core only to see if it does any good. Any thoughts or comments?

Thanks

If your heater core is causing puddles of water under the car, you should have water inside the car under the floor mats as well. You should be able to send the coolant when you're driving around.
Maybe one of the hose connections to the heater core at the firewall is leaking???

The heater cores of the W201 are known for an occasionally leaking one...I exchanged several in the past and have never tried a coolant additive to close a leak in the system...

greetingz,

Coolant Leak
 

Thanks. I looked under the carpet but didn't see any signs of leakage. I don't smell coolant inside the car, although I get a little fogging when the heater is on, but nothing serious. I looked between the inner and outer firewalls and didn't see any signs of leakage where the hoses connect to the core. My thought is that the core might be leaking inside the heater housing, and the coolant is then draining out the condensate drain for the AC heat-exchanger.

I would be hard-pressed
 

to put anything in there that would promote plugging. The answer is to fix what is leaking.
Jim
'85 300D
'95 E320
'97 CRV

Stop Leak? Leaking heater core?
 

Replacing the heater core is a very lengthy and thus costly job (20 hrs or so). MBZ put a lot of faulty design heater cores in their cars and lots have cracked and leaked. (This NEVER happens in U.S. 'junk'!)

The BEST stop leak is called "AlumaSeal', is a very fine aluminum colored powder that comes in aluminum colored plastic tube (1" dia x 3 " tall) It DOES NOT plug up any coolant passages what-so-ever, only very fine cracks and pinholes.


At a cost of about $3, it's worth a good try before laying out $2000+ for heater core replacement. No need to drain anything other than enough coolant to get it flushed into the circulation coolant.

Me, too!!
 

I have a 1990 190E 2.6. Same thing. Leak is coming from somewhere by the firewall on the driver's side. I checked the hose-to-core connection and found no dampness or residue. Just like DAVEK, there is no coolant inside the car.

Can anybody out there help on how to access the core. Do you come in from under the dash? Specifics would help tremendously. Thanks in advance.

I would suggest that you check the heater valve which is located between the firewall and bulkhead under the wiper grille near the battery.

JMike, DAVEK,

If you remove both lower dash panels (left and right), you can see the heater pipes coming through the firewall and going to the heater core. You can check that part of the heater system for leakage as well.

If the heater core is leaking, you should notice it inside the car. There has to be a kind of coolant smell and the (front) window(s) will get fogged...

The only way to get to the heater core is by removing the complete dash (steering wheel, console, and a lot more). It seems like a lot of work, but once somebody has done it before the repair can be done within 8-10 hours (Kebowers, were do you have your car serviced?)...

greetingz,

MBenz, thanks. I'll check that out. Chowpit, that's on the right side and that was replaced a long time ago. Thanks just the same.

Using stop leak will only prolong the agony, and not make solve the problem. Better do a thorough exmination to determine source and plug it once and for all.

Coolant Leak
 

I'll pull the lower panels and look at the pipes. I've looked at everything between the motor and the inner firewall and no leaks there. It must be within the passenger compartment.

I'll check-out the aluminum stop-leak stuff. I saw some copper stop-leak at the car parts store also. Has anyone used it?

These products should be pretty easy to use. And by running the stuff only through the heater core, I can avoid exposing the interior of the engine to whatever damage they may cause. I figure that for about $10 and one-hour of my time, I should be able to plug the leak. Even if it only works for a couple months, it's not much of an investment in time or money.

The water that runs through your heater core is the same as the water that runs through the engine...so I think that it will not be possible to avoid exposing the interior of the engine to whatever damage they may cause...

greetingz,

Thanks Mbenz,

I intend to disconnect the heater feed hose at the engine block, and the return hose at the auxiliary pump. I'll then flush the heater core and run the stop-leak through the core only, pressurize the stop-leak filled core with compressed air for awhile, then drain and flush the core, re-connect the heater hoses, and top-up the cooling system.
I thought I'd also pre-heat the stop-leak solution before filling the core.

How to use stop leak
 

Your proposed use of the Alumaseal probably will not work. It takes circulating hot coolant with the particles in it to carry the stuff to the leaking spot. AlumaSeal WILL NOT plug up anything else, not even the small air vent ballcheck valve in the thermostat. It stays circulating, doesn't settle out in low flow areas or stuff like that. It is the same weight as the coolant so it just goes along for the ride.

Stop Leaks
 

Hey All,

If you are considering using a stop leak, think again. The aluminum and copper particle stop leaks are "unhealthy" in a sense that they have tiny (and ABRASIVE!) metallic particles flowing through your radiator, heater core, block water passages, cyl. head water jackets, thermostat and housing, and your water pump impeller. The Non-abrasive sealants like Bars-Leak and KW work fairly well but are hell to get out of your cooling system once repaired. My girlfriend had a "tire place" work on her car while I was out of town and they put some in as "preventative maintenance". Three flushes and 2 months later and its still not all out, when I first saw the tiny brownish swirls and balls floating in the recovery tank I nearly flipped thinking that the headgasket was bad until I got some of this sticky brown "gunk" on my finger and figured out what it was. I would seriously suggest doing it right, stop leaks either inhibit flow through narrow passages, are abrasive to the cooling system, or are snake oils.

Best of luck.. BTW if you dont want to shell out for a new core or radiator, you could always solder the leak

Jason M.