over heating after driving @half hour noticed water running from bottom of car on front passenger side behind front tire.thought blown head gasket but checked plugs and no moisture checked dip stick only oil no water checked trans dip stick,only fluid no milky dew.Where is water comming from under passenger side from behind front tire.also bypassed heatercore & water still runs out

How did you bypass the heater core? That would not be very easy to do....in fact properly fixing it probably would be easier!

Is the water on the ground coolant? If its coming from where you say then one of the climate related hoses are probably leaking.

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What i meant by bypassing heater core was to disconnect the water flow to the heater core and plug the other hose so no water would flow through the core.water still leaked from under the car,not just dripped but poured out. When the car got hot,heard some type of sensor buzz sound from inside the car appears to come from the passenger side,faint but noticeable.Can you tell me what climate hoses you are refering to.Would like to stop the water from leaking but difficult to trace from under the hood to where the water actually leakes on the ground.Hoses dissapear into the body of the car from the battery area

The hoses that pawoSD are referring to go from the passenger's side of the engine, over to the little pump mounted on the subframe rail just below the expansion tank, then up through the partition to the heater valve, which is right next to the battery. From the valve the hose runs underneath the battery tray and to the nipple on the heater core that sticks through the firewall. The buzzing noise could be that heater valve malfunctioning in some way, I suppose, or maybe the aux. coolant pump doing something strange. Another possibility for the buzzing noise is the aspirator motor for the climate control temperature sensor. It's mounted right next to the glovebox in the dashboard.

Another possibility for the coolant coming out behind the wheel: coolant might be overflowing the expansion tank and going down into the overflow tank, which is mounted inside the fender, right behind the wheel on the passenger side. Coolant could be overflowing this tank as well. I would check the coolant for hydrocarbons to see if exhaust pressure is getting into the cooling system. This would indicate a failed head gasket. Unusual, from what I've read, for an m103 head gasket to fail in this manner, but it's possible.

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If coolant is overflowing, its normal for it to leak out by passenger front tire as that is where the over flow hose runs into a container to catch the fluid, but your container must be full, thus it pouring out onto the ground. As far as overheating, start with simple stuff first that doesn't require you to throw parts at the car hoping to fix it. Viscous fan clutch not engaging, thermostat by water pump housing not working, or even air in the system. Search posts by ps2cho because I think he has the same year and model as you and see if he has encountered this problem.

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1990 190E 3.0L

the info you gave me seems to fit the symtoms for reparing my car. I wll try the repairs and i will be intouch.Thanx

May just be the cap on the expansion tank aka radiator cap.

What color is the coolant now? If it is not MB or Zerex and especially if it is green then drain it all out of there, replace the thermostat like lsmalley recommends including the seal, then refill with 1/2 distilled water and 1/2 Zerex G05 or MB.

If it is green or you know it is not MB or Zerex you may want to flush the system after draining the old stuff out. I found a couple of pounds of citric acid on ebay for $10 delivered.

Drain the coolant and fill with citric acid mixed with 2.4 gallons of water to flush (run at operating temperature about 5 minutes). Then flush with water for an hour or so and flush/back-flush heater.

Check the first post in this thread.
OZBENZ - Australian & New Zealand Mercedes-Benz Forums • View topic - Let sleeping dogs lie.

The hose at the rear of the engine can leak. The coolant will drip down the side of the engine, onto the crossbar under the engine and drip off near the passenger side wheel.

Check underneath the hose for a leak.

There's also a rubber grommet on the engine attachment.