Heating - Page 2 - PeachParts Mercedes-Benz Forum

tobybul · #16 10-20-2009, 10:09 PM

I understand what you are saying TF. However, the aux pump does matter with the W123s. Thats the reason why MB put it there.

I'll try what you suggested Graplr, to power the pump separately.

Graplr · #17 10-21-2009, 10:00 AM

Quote:

Originally Posted by tangofox007

I am sure that every car has it's own set of characteristics.

Agreed.

Quote:

Originally Posted by tangofox007

If I disconnect my monovalve power, I get way more heat than I can stand. And that is with the aux pump not running.

Perhaps climate makes a difference. It gets a bit colder up here. Way more heat than I can stand is a relative statement. My wife can never get enough heat in my car in the winter while I am plenty warm after about 15 minutes of driving.

Quote:

Originally Posted by tangofox007

There are plenty of cars that are not equipped with aux pumps and their heaters work just fine. If the belt-driven water pump isn't pumping adequate coolant at highway speeds to provide heat, there seems to me that there has to be a problem greater than an inoperative (or non-operating) aux pump.

I think I would be swapping monovalves and backflushing the heater core.

I've swapped monovalve with a new one and done several coolant flushes over the life of the car. No changes in my heat output. And I run around all winter WITH the monovalve unplugged. The best thing I did for me was to put the pump on a switch. I guess the only thing I haven't done is put a new water pump in but I have had two different engines in the car since I've owned it (thus two different water pumps) and the heat output has been the same so I don't think that is the problem.

So in my car, the pump manually switched on gives me the best heat in the winter.

tangofox007 · #18 10-21-2009, 10:34 AM

Quote:

Originally Posted by tobybul

I understand what you are saying TF. However, the aux pump does matter with the W123s. Thats the reason why MB put it there.

The aux pump "matters" when it comes to having consistent heat at low engine rpm's. The belt-driven water pump should have no problem whatsoever providing adequate coolant flow at highway speed. If it could not, would it not stand to reason that MB would have designed an aux pump into the engine cooling system as well?

There have been a number of reports on this forum where members bypassed their aux pumps with good results. I am not buying the notion that an inop aux pump can cause a major degradation in heater operation if everything else is operating normally.

tobybul · #19 10-21-2009, 12:48 PM

Quote:

Originally Posted by tangofox007

..........
There have been a number of reports on this forum where members bypassed their aux pumps with good results. I am not buying the notion that an inop aux pump can cause a major degradation in heater operation if everything else is operating normally.

Thanks, TF.

I can't say mine is a major drop in heat. It does keep the interior warm - eventually. What I am after is hastening the time it heats up just like in my 85D. I have not measured the output air temp from the registers but I know that it is about 30-50% less than in my 85D when in full heat b4 it modulates down.

Of course, the interior warms up faster or slower relative to the outside temp. I have about a 20 min drive to work. at 30 deg F outside, the interior warms up in about 10-12 minutes on the 84D at full heat but in less than 5 min on the 85D set at 22 deg C (with the working aux pump).

rosenfe · #20 10-21-2009, 01:03 PM

i too am experiencing similar problems,i recently had been having erratic heat and cold coming out at the wrong times.i changed monovalve-even though it did not look damaged,no change,then put in a different functioning solenoid,now mostly cold with no heat.unplugged monovalve still mostly cold even in defrost mode.do not hear aux pump come on with key on.what i dont understand is why with original solenoid and new monovalve mostly heat and difficulty getting ac,different solenoid no heat???.car is 85 300d

tangofox007 · #21 10-21-2009, 01:18 PM

Quote:

Originally Posted by tobybul

What I am after is hastening the time it heats up just like in my 85D.

If the slow increase in temp is also reflected on the temp gauge, a new thermostat might be in order.

Squabble · #22 10-21-2009, 01:23 PM

i have been having some problems in a similar vein. they're described here: CCU Problem: A Sign of Worse Things To Come?

based on this, i ordered a new water temp switch from all parts express that will be arriving tomorrow. i'm banking on this little thing fixing both my weird heating issues and glowing issues. who knows though...

i'll write back if all goes well. i suspect this more in my situation because i replaced my t-stat housing this summer (where the switch is located) and put in one from a junkyard. the rubber in it also spins pretty freely...

check yours and check the wire that comes from the top of it. could be?

tobybul · #23 10-21-2009, 10:44 PM

Quote:

Originally Posted by Squabble

.......
i'll write back if all goes well. i suspect this more in my situation because i replaced my t-stat housing this summer (where the switch is located) and put in one from a junkyard. the rubber in it also spins pretty freely...

check yours and check the wire that comes from the top of it. could be?

I wonder if this temp sw is connected to the ccu which then tells the aux pump to run....

tangofox007 · #24 10-21-2009, 11:03 PM

Quote:

Originally Posted by tobybul

I wonder if this temp sw is connected to the ccu which then tells the aux pump to run....

As best that I can determine by looking at the schematic, the cold engine lock-out switch plays no role in the operation of the aux pump. It appears that it affects only the blower and fresh air flap operation in the EC and NORM modes.

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