overheating troubleshooting 84 190E - PeachParts Mercedes-Benz Forum

#1 09-06-2002, 01:26 PM

Still overheating !!! I've done flush, new rad cap, new thermostat, and now fan clutch. Aux fan do not engage at all. What's next?? Also, is it possible to get relays, sensors, switches, etc. tested anywhere locally before I replace them needlessly??? Frustration and aggrivation are mounting.

Piotr · #2 09-06-2002, 10:05 PM

need more info- aux fan should engage only with AC on or gross overheating. if you have electromagnetic clutch I'd be amazed if it was bad. Did you change your $21.39 fan switch (on top of the water return from the radiator)??? also, is it overheating while driving? if you get over 100C on the road, you need a new radiator (fans work only at speeds below 40 mph, after that the flow of air is sufficient to cool it down). I had the same prob-non MB mechanic told me my clutch was bad (idiot). then 2 MB certified MB mechs told me my temp was normal. Then I found out my fan switch was bad (so called 100-110 switch- kicks in the main fan at 110C and runs until temp falls to 100C).

#3 09-07-2002, 01:52 PM

The aux fan doesn't come on at all, period. The temp used to stay at 80C, now it seems to be very erratic--between 90-100 under the same conditions (on the freeway). But as soon as I get into traffic or in the city, the temp immediately starts to climb. If I stop at a light, it climbs and I don't have to sit there for very long, within 5 minutes. I just bought a new fan clutch and had it put on, but there are no changes at all. Do you know if anyone will test the switches to make sure they are faulty before I spend the money to replace it. But the fan switch sounds like the next solution. I'm there. Thanks

pentoman · #4 09-07-2002, 07:14 PM

Can't believe you did the clutch before the fan switch!

Fan switch is by far the most likely culprit, here it is circled in green, costs very little, let's hope that's what it is.

You can test it by pulling the plug off the top, and then shorting the 2 pins (female pin holes) on the plug. This is all that the fan switch does, gets to a certain heat then shorts the pins. Should come in at a little over 100 C, mine does around 105 C.

The actual fan switch is the bit which screwes into the engine that has the 2 male pins.

If you pull something that doesn't have 2 pins, you may have the wrong thing.. you probably wouldn't want to short the wrong plug.. wait till someone confirms this *is* the fan switch... I'm 99 percent sure, but it was a few months since I did mine so it may have 'moved' in my memory

later!

haasman · #5 09-07-2002, 07:17 PM

Russ, you are the man! How did you put the green circle on the image?

Haasman

Piotr · #6 09-07-2002, 11:47 PM

looks like a bit map job to me. By the way, the aux fan may be bad, or have the blown fuse (maybe because the aux fan motor is corroded-personal experience). I vote (100%) for the fan switch. The best known syndrome is what you described - temp skyrockets in traffic. My suggestion is for now turn your heater on max to protect your engine. however, it may be too late. My temp is also erratic, but never goes over 100C while driving (after replacement of a radiator). I believe it may be an indication of a blown headgasket

sunil190e-1.8 · #7 09-08-2002, 04:28 PM

i am also pretty sur it is the coolong fan switch.
my car used to overheat in idling conditions in traffic.
i replaced the cooling fan switch-mine was a 3 pin one, as my car has a 1.8 litre engine.-problem solved
if you get the faulty switch out and type in the part number which is stamped on it, into the fast lane online catalogue website -you will be able to see a picture of what you can order-it is not expensive but as russ says your switch may be a 2 pin type as you might have a 2.3 litre engine.

pentoman · #8 09-08-2002, 05:00 PM

The image stuff is not hard if you have the right tools

i just zoomed the digital camera photo using Paint Shop Pro, and used a translucent paintbrush.. it's powerful software for image manipulation, quite scary what you can do with it

Oh by the way, test the fan switch with the engine running! Though it may work without engine running.. anybody know?
It never gets hot enough in England for the aux fan to engage often..

later!

edited: transluscent paintbrush, not opaque, duh

haasman · #9 09-08-2002, 05:18 PM

thanks Russ I'll check the program out.

Have you done a 190E heater core? I've got a post going regarding getting one of the inlet/oultet pipes out so I can check the O-ring. Do you have any idea?

pentoman · #10 09-09-2002, 09:37 AM

haasman - I just read that post.. sorry I can't help with that. Can't think why someone would have bypassed the heater core..

Did it work yet 'lett me' ??

haasman · #11 09-09-2002, 09:43 AM

Russ It seems they bypassed it because it is leaking.

This a project car for my daughter. Her first MBZ. This is going to be one heck of an education ....

#12 09-12-2002, 12:31 AM

Well, I've replaced the fan switch yesterday. However, I noticed in doing so, the new one doesn't exactly look like the one being replaced. The old one has a long stem that is about 1.5 inches longer than the threads to screw in. I'm taking both parts in tomorrow to see why the parts are different. And it's still running hot. I'm not in the position to buy a new radiator yet, since I've checked on the price in the parts shop here. My parts store here in San Diego has got very good prices too (about the same). Thanks for all the input and I'm still checking. Is there that the sending unit could be the problem???

Piotr · #13 09-12-2002, 09:24 AM

AARRGGGGH !! i was sooo sure... . Define "running hot". Also, make sure that the dealer gave you the right part (common problem). see what temp is stamped on the switch- the higher one is when the fan engages, the lower when it disengages. If your engine temp is below the temp switch is rated for (the higher one) you are not overheating. also, check if your main fan is engaging. really, the whole circuit consists of a switch, fan, and a fuse. Unless there is a relay somewhere. also, if fan does not work it could be your wiring.

190dee · #14 09-12-2002, 02:40 PM

Pentoman is right about the switch test. Lift the connector a bit but do not remove it. With car running shorten the pins with a screwdriver. You should hear a click as the fan cluth does engage and the speed of it will increase. You can't really miss it because it start to blow a lot of hot air at you. This is on 190 E with 2 pins

On the 190 Diesels the switch has only got one pin and you can test this switch by pulling of the whole connector and insert a small screwdriver into it. Then you ground screwdriver at for example on the valve cover and voila...cluth does engage. Otherwise there can be wire or cluth problems.

I did this a week ago so I haven't mixed things up yet...

Also...you stated you changed thermostat. Do you know at what temp the thermostat do open up? I have seen at least two thermos for 190E. One that does open at 79 degrees and the other 85 degrees (both celsius, I'm european

)

If you live in a "warm" area you should get the 79. Don't know if this is recommendable but you can boil the thermostat to see at what temp it do open...Measure at the same time and you got it. If you don't know which one you got...

And I'm not really a mechanic...just trying to help.