not too hot ! - PeachParts Mercedes-Benz Forum

#1 09-12-2006, 10:07 AM

I have't driven my '86 300SDL much this summer but now that the cool weather has hit Canada I'm driving it every day. My problem is that I am getting very little heat out of my heater. Is it possible that I have a clogged heater coil? How would I unclog it? What else could it be? Thanks.

TX76513 · #2 09-12-2006, 10:26 AM

Quote:

Originally Posted by djoyce93

I have't driven my '86 300SDL much this summer but now that the cool weather has hit Canada I'm driving it every day. My problem is that I am getting very little heat out of my heater. Is it possible that I have a clogged heater coil? How would I unclog it? What else could it be? Thanks.

My personal 02 cents would be to check your coolant level - if it's good then thump your mono valve with a rubber hammer, it's probably stuck and very common going into fall problem with mine.

redassag00 · #3 09-12-2006, 10:30 AM

Do you mean heater CORE?

#4 09-12-2006, 10:41 AM

Sorry, yes I meant the heater core! I will check the coolant level, where is the monovalve and what does it look like?

SD Blue · #5 09-12-2006, 11:07 AM

The monovalve is between the firewalls, near the center and has a small 2-wire connector. Here is a link to a photo:http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1W71C3A361W90NKHVR&year=1984&make=MB&model=300-SD-002&category=R&part=ACC+Mono+Valve&appChassis=_any

The most visible part is the plate with 4 small screws. There is a rebuild kit which is about the easiest job you will ever do on this car. Remove 4 screws, replace innards, & restore.

#6 09-12-2006, 11:27 AM

I checked and my coolant is full, I'll give the monovalve a tap and see what happens. Hope it works, winters are real cold up here!

#7 09-12-2006, 11:31 AM

By the way, could it be the heater core? And if it is, would flushing it make a significant difference?

AlanTbird · #8 09-12-2006, 11:36 AM

my 86 does the same thing!
I got a valve and a PUMP to put in it for this winter.
still 100 degrees here so I have time!

cheers

rrgrassi · #9 09-12-2006, 02:16 PM

If the heater core is really plugged, a flush may not work. If it is plugged because some smart person used stop leak, then flushing it will remove the stop leak and allow coolant to visit your floorboard.

If your car has an AUX waterpump like the 123, check it's operation as well.

TX76513 · #10 09-12-2006, 02:44 PM

bill murrow · #11 09-12-2006, 04:13 PM

At what temp does the car run when fully warmed up?

My 240 had the same problem but it was the t-stat remaining open.

Cheers,

Bill

carwithfarts · #12 09-12-2006, 04:43 PM

It got real cold here suprisingly and my heat just quit working. sometimes it would start but it would never get real warm. I replaced the thermostat and viola! i have heat now. its a cheap fix if thats a problem and if it hasnt been replaced in the last five years it might be a good idea to replace it now.

#13 09-13-2006, 07:50 AM

Unfortunately the problem is not the thermostat, the engine hits proper operating temp with a few minutes. Is the heater core behind the dash?

SD Blue · #14 09-13-2006, 10:36 AM

the heater core is behind the dash. Removal would be a major PIA. That would be the last thing I would go for unless someone has used, as mentioned before, mass quantities of stop-leak. Usually I have found that heater cores have a problem with leaks not blockage.

In order of cost and suspicion, I would try:
monovalve
solder joints in ACC controller
aux. water pump