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Overheating m103

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absoluteanc's picture
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Hi I am having a problem with my mercedes. This is a 2.6 liter version of the m103 and it is in a 1993 190E. The engine is identical to my 300E and I have always had a great response from this board

The head gasket was bad and leaking oil into the coolant. I flushed the radiator three times before putting new coolant into it after the head gasket replacement. The head was tested and cleaned by a foreign car machine shop. The car runs fine but when I try to bleed the system only steam comes out of the bleeder. The thermostat is opening but the system will not circulate, the heater core is bypassed and that hose is empty.

I think the overflow hose will have steam in it I cannot figure out if it is combustion or air? It is spitting bits of oil and I am not sure if its from before, so a chemical test might not be accurate. The temperature does climb to 120 after about 20 minutes, I try not to get it that hot. When I remove the thermostat housing the engine has no coolant in it??? If it is a bad head gasket again wouldn't coolant still circulate?

To anyone that knows anything about this engine and the cooling system any advice would be greatly appreciated.

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Re: Overheating m103

Did you burp the cooling system when you refilled it? Cold engine, remove one end of the upper radiator hose. Pour coolant into the engine til full. Then pour coolant into the radiator until full. Bring the engine up to normal operating temperature and top off the coolant tank as neccessary.

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Re: Overheating m103

No I did not do that the first time. I have tried to pour it in til full with the thermostat removed last night. Maybe I should drain the coolant and try again. I have ran out and have been topping off with water. I have went through 4 gal of mix and 1gal of water. I am worried there is too much water and there is still oil shooting out the over flow.

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Re: Overheating m103

You have managed to put 17 quarts of liquid into a 10 quart system. If it's not on the ground then it is going out the exhaust pipe. Does the exhaust feel wet? Have you done a compression check? Not sure about the oil source except that it may be coming from a blown head gasket.....again. If you pull the head again, have it leak tested and check the block and head for level.

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Re: Overheating m103

No the coolant was collected and will be disposed of, some landed on the ground because it just kept over flowing out of the tube. I bet your right I did not fill it properly. I have never done a head gasket I was so concerned on doing it right that I oversaw refilling the system the way you discribed. I feel much better knowing it was probably a rookie error hopefully the engine didn't get hurt. Your link states that 130 is the max I might have hit 118 at the most.

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Re: Overheating m103

If your aux fan and the rest of your cooling system are functioning properly, you will know when you are in the overheat mode. It will sound like a piston engine, propeller driven airplane on takeoff. It is a distinct sound, rarely heard from a car. Even then, the engine will survive a few minutes of this abuse. Turning on the heater at the highest temp will help move or keep the temp down. This is not a substitute for coolant. Only an emergency measure.

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Re: Overheating m103

is that the same sound as the fans turning on at around 110? it vibrates the car when they are on high speed. The cooling system was not working properly the engine would not let the coolant in when hot. I bought new coolant I will try to flush and fill it again.

Thanks for you help.

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Re: Overheating m103

Too young to have flown in a propeller airplane, eh. No engine will easily accept coolant when hot. It is like pouring wzter on a hot stove or fire. Downside with a car is the risk that you can crack the head or block.

Try filling it as I suggested using just water. If it stays in, drive it for a few days. If you like it, drain the water and refill with 50/50 mixture.

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Re: Overheating m103

It worked, I was able to properly fill it and it stays at 88. Thanks for your help. Sometimes you learn the hard way.

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Re: Overheating m103

We won, we won. A success story if I ever heard one. Good work.

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Re: Overheating m103

Robert Goodwin;163531 wrote:
We won, we won. A success story if I ever heard one. Good work.

Nice going, Robert. That's the value of a forum like this. To someone like yourself, there's no mystery to much of this stuff, but plenty of car owners out here, even enthusiasts, are puzzled by what to do about their situations, and a few pointers and some patience can save the day for the haggard owners. Now wouldn't it be nice if absoluteanc would send in his/her MBCA membership right now?

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Re: Overheating m103

Ok I did join, I didn't realize there was a paid membership. But I don't mind paying.

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Re: Overheating m103

Based on your ZIP Code,. you will likely be assigned to the Triangle Section. Lot's of great people in the organization as well as tips and leads to technical help and commercial services.

Welcome aboard. When you receive your membership info, besure to update your profile on this site.

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Re: Overheating m103

absoluteanc;163871 wrote:
Ok I did join, I didn't realize there was a paid membership. But I don't mind paying.

Full membership is more than signing up for the forum. You will get a great magazine with your MBCA membership. Access to club events. Also many dealers offer great parts discounts with your membership card. It will pay for itself.

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Re: Overheating m103

Robert Goodwin;163442 wrote:
Did you burp the cooling system when you refilled it? Cold engine, remove one end of the upper radiator hose. Pour coolant into the engine til full. Then pour coolant into the radiator until full. Bring the engine up to normal operating temperature and top off the coolant tank as neccessary.

The old fashion way to fill a radiator with cap was easy. Start with a cold engine. Drain the radiator and fill it to the top. Run the engine until thermostat opens and radiator has more room to fill. Once you fill the radiator to the top, install the radiator cap and you are done.

However, my mercedes 1995 E300 Diesel 190K miles, does not have that option. Right now I feel I have some air in my cooling system. I have a 85 degree thermostat and temperature holds at 85-87 degrees, but auxiliary runs most of the time while I am driving slow or stuck in traffic. That I think is wrong when outside tempratur is around 45 degrees. First few years I drove the car, I do not think this was the case. For last 8-9 years, after antifreeze change, I have been noticing this problem. The return hose to radiator, does not seem very full. Did not think about air in the cooling system until recently. The problem is there, even without running the air condition at 45 degrees temperature outside, that does not make sense.

Your suggestion looks pretty good to fill the radiator. By taking the return hose off, filling the engine first, you get most of the anti freeze in the engine. Then fill the radiator to the top.

If I follow this route, there would be some air left on the top of the radiator, that you can not fill, until thin rubber hose going to overflow tank is used to fill the rest of the space in the radiator. This hose goes to the top of the overflow tank, so not sure how it will suck antifreeze that is filled half way at the bottom of the tank. I would think the air would be sucked in first from the overflow tank rather than the antifreeze. Is my assumption wrong?

If my assumption is correct, how does the overflow tank used to get the anti freeze in the radiator, if there is a leak and radiator loses coolant?

What is burp?

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Re: Overheating m103

Filling the cooling system the old fashioned way doesn't usually work well on a Mercedes. The method I prescribed is right out of the manual. What you are referring to as the overflow tank. If you follow the small hose from the neck of the filler cap, you will come to the overflow tank mounted in the back part of the right front wheel well. Your cooling system is pressurized by about 20 PSI. That is to raise the boiling point of the coolant.

Excess heated coolant travels under pressure through the small hose at the top of the radiator to the expansion tank. Coolant is returned to the engine through the approx 25 MM hose on the bottom of the expansion tank.

A leak anywhere in the closed system will result in some other outcome based on where the leak is.

If after a drive, your expansion tank is full, the system is likely full especially if the temperature is normal. If not, top it off (remove cap carefully as the system is under pressure).

As regards your aux electric fan running, you have 2 of them. Are they both running or just one. If both, the switch on your A/C receiver drier is suspect but not very likely. If only one is running, romve relay K9/1 or K10 in the fuse box under the hood. If that doesn't stop the fan, swap the relays. If that swaps the problem, replace the bad relay. They are 14 years old and don't last forever.

Let us know how this works out.

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Re: Overheating m103

Filling the cooling system the old fashioned way doesn't usually work well on a Mercedes. The method I prescribed is right out of the manual. What you are referring to as the overflow tank. If you follow the small hose from the neck of the filler cap, you will come to the overflow tank mounted in the back part of the right front wheel well. Your cooling system is pressurized by about 20 PSI. That is to raise the boiling point of the coolant.

Excess heated coolant travels under pressure through the small hose at the top of the radiator to the expansion tank. Coolant is returned to the engine through the approx 25 MM hose on the bottom of the expansion tank.

A leak anywhere in the closed system will result in some other outcome based on where the leak is.

If after a drive, your expansion tank is full, the system is likely full especially if the temperature is normal. If not, top it off (remove cap carefully as the system is under pressure).

As regards your aux electric fan running, you have 2 of them. Are they both running or just one. If both, the switch on your A/C receiver drier is suspect but not very likely. If only one is running, romve relay K9/1 or K10 in the fuse box under the hood. If that doesn't stop the fan, swap the relays. If that swaps the problem, replace the bad relay. They are 14 years old and don't last forever.

Let us know how this works out.

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Re: Overheating m103

Filling the cooling system the old fashioned way doesn't usually work well on a Mercedes. The method I prescribed is right out of the manual. What you are referring to as the overflow tank. If you follow the small hose from the neck of the filler cap, you will come to the overflow tank mounted in the back part of the right front wheel well. Your cooling system is pressurized by about 20 PSI. That is to raise the boiling point of the coolant.

Excess heated coolant travels under pressure through the small hose at the top of the radiator to the expansion tank. Coolant is returned to the engine through the approx 25 MM hose on the bottom of the expansion tank.

A leak anywhere in the closed system will result in some other outcome based on where the leak is.

If after a drive, your expansion tank is full, the system is likely full especially if the temperature is normal. If not, top it off (remove cap carefully as the system is under pressure).

As regards your aux electric fan running, you have 2 of them. Are they both running or just one. If both, the switch on your A/C receiver drier is suspect but not very likely. If only one is running, romve relay K9/1 or K10 in the fuse box under the hood. If that doesn't stop the fan, swap the relays. If that swaps the problem, replace the bad relay. They are 14 years old and don't last forever.

Let us know how this works out.

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Re: Overheating m103

I saw two hoses connected to the overflow tank. One that comes from the top of the radiator, the other near the cap to drain coolant if over tank is full and more coolant is coming in.

However, the third hose that is at the bottom of the tank to return coolant to the radiator, I did not know about. I will have to find it.

Both auxiliary fan turns on when the A/c is running. That is normal.

Neither fan turned on when A/C was off, Car use to get hot to 100+ C degrees. So we replaced the coolant heat temperature sensor on the top of the engine and now only one comes on when I am driving either slow or I am stuck in the traffic even at 45 degrees F.

Recently, the coolant was replaced. Initially the heat was not coming in. However, after driving half hour, the heat started working and overflow tank was refilled to 2/3 level of the tank. Now it is holding at half the level for last one month.

When car is hot, I expect the return hose to rediator should feel hard. Mine is soft. Auxiliary fan running at 45degrees F does not make sense. That is why I am suspecting air in the cooling system.

Now I need to make sure there is no air in the cooling system, so coolant instead of air goes through the radiator and cools the engine more efficiently.

I have two options.

One to follow your instructions. Second to run the engine hot, with heater fully on while cap is off and see if cooling system pushes the air out and sucks more coolant in. If my second method does not work, I will have to go to your method to burp to get the air out.

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Re: Overheating m103

The top and bottom hoses on the expansion tank are what allows the coolant to circulate to/from tank and radiator. As for aux fans, if I'm following your explanation, you get both fans with A/C on, and since your coolant temp sensor replacement, you get only one fan when driving slowly or stuck in traffic. That may be correct, but I doubt it. In cars with 2 fans, I believe that both fans should either be on together or off together. They should be on low speed if A/C is running and the engine temp is below about 105C, or on high speed if the temp is 105C or above (whether or not the A/C is running).

According to Arthur Dalton, there are 3 quick tests you can do to isolate fan problems. In each test, the ignition key is ON:

Test 1: Disconnect the 2 wire connector from the blue coolant temp sensor; that will default to high fan.

Test 2: At reciever/drier, there is a sensor with a 2 wire pigtail..slide the insulation sleeves back at the end of pigtail and jumper those 2 wires ..that will get you low fan.

Test 3: Bring a jumper wire over to the R15 resistor (behind driver headlamp) from battery positive. Jumper to the single wire on R15 will get you low, jumper to the 2-wire side of R15 will get you high. If NO, then the fans are bad (or wiring to fans).

If NO on first 2 tests, you have a fuse, relay or resistor problem...If YES, then you have a low refrigerant problem.

The first 2 tests verify sensor circuits, the last test verifies the fan motors.

Apart from that, there's bound to be something else going on for the engine to run that hot with ambient temps in the mid-40s. A properly running 103 motor should remain somewhere between 85-95C even in slow traffic with ambient temps in the upper 80s to low 90s, as we've got now in South Florida.

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Re: Overheating m103

thanks for all your help and suggestions.

Because of a wedding in the family, I have not had a chance to work on the car.

My mistake, not one but both aux fans turn on when the car gets hot between 85 to 93 degrees C. Both fans turn on when A/C is on when temperature starts going up. So I do not see a problem with the fans.

I had already tested the fan with the coolant temperature sensor before I replaced the coolant temperature sensor. If I disconnect the wires from the coolant temperature sensor, the two aux fans do turn on.

One more thing I observed was at higher rpm during idle, temperature goes down. That may be because additional air flow from inside fan, that is running at higher rpm with the engine.

I just need to make sure coolant is running fine through the system without air.

I do have enough information that you provided, so once I get a chance I will work with your info. Right now the temperature holds fine between 85-93 degree C, so I do not see a serious problem that I need to look at immediately.

Again, thanks a lot for your help.

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Re: Overheating m103

One other thing to check is the direction the fans are turning. Should be clockwise looking at them. Ultimate test is to check airflow with a strip of paper. Fans should try to suck the paer toward the radiator.

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