Hi

First of all i must congratulate all the members here for an awesome site.

Now to my problem,
After a month of having the new evaporator, my a/c would not start at all. My mechanic told me there was no refrigerant and there must be a leak. he said it leaked from some evaporator valve and he fixed it up. After this my Auxillary water pump started leaking and then stopped working completely

I have searched the threads here and what i understood was that you can plug off a defective auxillary pump if you do not need the heat. Thats what i did as i reside in dubai where the temperatures are quite high infact they are now 45-47 C in the day time. also as the pump was leaking badly, I connected the hoses directly and threw of the pump. I also thought this might help the climate control to maintain better cooling as my a/c even after a new evaporator is not good enough.

I had also read that the pump also helps in maintaining engine temp. so last evening when i took the car out for a drive. i kept an eye on the engine temp. the outside temp was 39C and it was bumper to bumper traffic my engine temp rose upto 110C. Also the car just went dead when i accelerated and braked at the traffic lights. After that i restarted the car and it was normal but the engine temp was 110C. Is this normal.

Does this mean i have to put in a new auxillary pump. Can someone please tell me what and how does the auxillary pump really function. Also should i put in 1 amp fuse with the new pump.

KK9
1989 300CE

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300CE 1989 Euro Model.
ML350 2011.

What engine temperatures were you reaching in similar conditions prior to the aux pump going out?

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Jim

I really never noticed that before, but i believe it was around 90 to 100C. It never went upto 110C. I am sure I would have noticed if it had been so high.

The aux water pump is only used when the automatic climate control is in heating mode, it is not used for engine cooling. It supplements the main water pump helping move more coolant thru the heater core, really only beneficial when the car is idling or when running the heater when the car is off.


Is the electric aux fan coming on with the a/c?

Chris

Yes it does come on.

The aux fan on your car is supposed to come on at 107C on high speed . Do you know if it was running at high speed when the car was at 110C? You can test the fan by pulling off the connector on the blue two prong temp switch on the engine. The fan should then come on high speed.


Chris

By high speed do you mean the car or the blower. Anyway the car was in low speed as there was too much traffic. Also the a/c blower was in low speed as the a/c does not really cool well in auto or high speed. only get a lot of air but not really very cool.
Now to add to all the trouble my battery is completely discharged.I foolishly left my cabin overhead backlight on and now the battery is dead.Tried to get it recharged but it does not charge at all. Getting a new battery and also asked my mechanic to check the fan and the monovalve too.
Anything else i need to check.

Thanks in advance.

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300CE 1989 Euro Model.
ML350 2011.

I was talking about the electric auxiliary fan.

Chris

Sorry i overlooked that you mentioned the aux fan.
I am not sure whether it was running at high speed. I did not check. now that you mention it i remmember hearing it come on as i started the car after stopping for a few minutes to pick up groceries. My mechanic tells me he is going to check the thermostat. Any advise on anything else i need to check will be helpful.

After installing a new battery, I find the alternator is not good. It shows a charging voltage of only 11.8V . Could this be the cause of the engine heating.The aux fan could be running slow due to the low output from the batteries. I am only trying to think, dont know.I asked the mechanic to get a new alternator. Hope this helps. My old AC Delco maintenance battery lasted only 10 months. If I get a refurbished alternator what should I check. Any advise is appreciated.

Got a refurbished 120 Amp alternator.It did not charge at all. Returned it back and got a new 90 Amp bosch alternator. Checked the voltage of the new 66 amp A/c Delco battery it was 12.4V. Checked for voltage without any load and only the engine running it was 13.4V Checked again with all the lights on at high beam, the A/c on with high blower speed.The radio also on, found the voltage to be 12.4V. I had read somewhere in this forum that the voltage from the alternator should be from 13.5 to 14.5V with or without load.
Please will someone tell me what to do.Is this OK or should I ask the mechanic to change the alternator. I believe all my problems were related to low output from the previous alternator.

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300CE 1989 Euro Model.
ML350 2011.

Anybody Please

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300CE 1989 Euro Model.
ML350 2011.

That voltage under load sounds ok to me. To be sure, add the rear defrost(if you have one in Dubai) to your load, and test it at 2000rpms.

Bet you will get 12.57volts, which is expected.

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1986 300E 5-Speed 240k mi.

Installed a new 120 amp alternator and a 66amp 12V AcDelco battery.

I have a rear defrost but havenot checked the voltage with it on.
Will do it tommorow and let you know. Also added another direct wire from the battery to the alternator.

Got the car checked by an autoelectrician. He tells me i have to get a 14V Bosch battery for this car and not a 12V battery or any other battery.
Is this right. Do The mercs use a 14V battery.

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300CE 1989 Euro Model.
ML350 2011.

You certainly do not need a 14 volt battery for your car. I had a 300CE Euro and it had the normal 12 volt Bosche in it ( capacity I cannot recall ) I would be interested to hear who in Dubai is doing the troubleshooting for you. Might I suggest you call my people in Rashidya who certainly know heaps about Mercedes cars and they look after mine very well indeed. Call them on 04-2852800, ask for Ben and good luck !

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1993 190E 2.0L (Euro.) sold
1991. 500 SEL (Euro.)
1991. 300 CE (Euro.) sold
1993. 500 E (U.S. spec.)