Running Hotter Than Normal - PeachParts Mercedes-Benz Forum

chrisalex78 · #1 10-13-2003, 07:18 PM

Allright guys and gals I need some advise. I have had a problem with my girlfriends 83 300D turbo running hotter than it used to. I noticed it one day and then changed the t-stat and flushed the system, which only made it run even hotter. Thinking it was a bad t-stat I exchanged it for another one which resulted in the same behavior. After reading on here and doing some searching I decided to buy a behr t-stat for it instead of the brand O'Rieleys carries, this once again had no affect on the temp.
The radiator does not appear to be plugged and seems to have good flow, the fan pulls air and seems to be working fine, and the water pump seems to be pumping the water because there is flow. This problem occurs at all speeds, either sitting at idle or running 80mph down the highway.
It is not getting in the red zone but it is staying around the 100C mark when it used to run no hotter then the 80C mark. I know some guys say that its fine as long as it doesnt get in the red but something is wrong for it to be reading that it is running this hot, and I want to find out what it is cause it is bugging me.
I have thought that it may just be the gauge giving a wrong reading (does anyone know where the temp. sending unit is on these??). The car has been having some problems with the tach also which works when it wants to and just recently the fuel gauge began jumping around as well as the temp gauge which will suddenly spike to 120C and instantaneously drop back down to around 100C. I have checked the connections on the back of the instrument panel and found nothing to be out of the ordinary.
Anyway if you have any suggestions or advise please let me know; it would be appreciated. Sorry to make this soo long but i wanted to include enough info for some valid advise.
Thanks
Chris

engatwork · #2 10-13-2003, 07:22 PM

Pull the radiator and have it flushed, search for "burping" the system and follow the proper procedure, make sure you run a little more water than MB coolant. Does it do it in traffic or out on the open road? If traffic then the fan clutch is probably tired.

chrisalex78 · #3 10-14-2003, 11:51 AM

It does not matter what speed it is going. Like I said above it can be sitting still or running 80mph down the highway, it still runs about 20C hotter than it used to.
I will give the "burping" thing a try some time this week and see if that does anything. Thanks for the advice
Chris

leathermang · #4 10-14-2003, 12:11 PM

Ok,,, these symptoms sound like you might have been running this temp all the time.. but you cleaned off the temp sending sensor and it is now sending a more accurate signal to the guage...just guessing from the things you describe...

#5 10-14-2003, 03:19 PM

I just got out of the same problem with my 81SD. The gauges began jumping around, and the temp gauge would climb and then flick back down. It started slowly last spring.
I bought a can of electrical contact cleaner and started searching for a bad connection. Went to the instrument cluster first. Traced the harness to a buss in front of the tach amp, mounted on the inside of the left front fender. That was the problem. It has some large pins and the connection between the male/female had corroded a bit. Some electical contact cleaner and some electical grease to protect and now the gauges work again.
Be carefull about the position the buss plugs in. Easy to get it backwards. Then the gauges will freeze in one position. Just unplug and reverse.
Took a while, but I didn't spend that much time on it. Easy fix.

chrisalex78 · #6 10-15-2003, 08:37 PM

Well I tried the burping thing today. I dont think that was the problem but I did discover something in the process that very well could be the problem.
I drove the car up a very steap little hill and pulled the upper radiator hose off, started the car and poured water in the hose as needed to maintain the water level (it really didnt take much at all). I let the car run like this for a while.
Well this is what I noticed, at about 80C which is what the t-stat is rated at, only a slight flow of water came out of the radiator where the upper hose goes. This flow did not increase even when the car started to get closer towards 100C. The flow of water was only enough to create a steady steam without dripping (a little larger than a piss stream) and reving the engine did not increase the flow any noticable amount.
So here is what I am thinking (please give me some feedback on this):

1. The radiator may be the problem even though it does allow a great flow when flushed out with a water hose

2. The water pump may not be up to par, never had this happen but i assume it could be a possibilty

3. whatever ideas yall come up with

Any input is appreciated. Thanks guys

Chris

Stevo · #7 10-15-2003, 10:02 PM

I think its pretty rare for a water pump impeller to go bad and not pump enough volume but it has happened.

If you have a spare T stat and want to try something, drill a small hole in the round part that covers the by pass. when the main part opens this round plate covers the by pass. Theres a big long explanitation of why this works, and it worked for me, but if you have no luck give it a try and see.

chrisalex78 · #8 10-18-2003, 12:07 AM

I had some spare time today and decided to pull the water pump off in order to eliminate it as being the problem. As expected the water pump looks fine, impeller turns freely and looks great. However once i had the fan shroud off i discovered that apprently the fan had magically came off for the previous owner and tore the radiator up pretty good. It has not been leaking or anything but the massive amounts of solder used to fix the gouges in it bother me. I went ahead and pulled the radiator out and I am taking it to a shop tomarrow to have it looked at.

Old Deis- Where exactly is the buss you refered to, i would like to take a look at it and see how it looks

Chris

adamb · #9 10-18-2003, 12:28 PM

You can get an OEM BEHR aluminum/ plastic radiator for about 245 or so. IMHO, this woukld be the best route to go, as it would restore optimal flow and maintain the vehicles OEM stature. Whenever I buy a vehicle over 8 years old or so, I feel paranoid about overheating, so I simply buy a new radiator and put it in. It may be wasteful, but the piece of mind for me is worth it.
Good luck, Adam Bush

LJ DERBY · #10 10-18-2003, 02:43 PM

OldDies,

I have an 83 300D that has gauges that jump once in a while, particularily the temp. I looked for that bus in front of the tach amp and only found one connector. It only has 2 wires and is keyed so you cant put it together wrong. Does this sound like the same point to you? I cleaned it with contact cleaner and will see if it still acts up today. Thanks for the hint at what has been an annoying problem. LJDERBY (Salem, Oregon)

chrisalex78 · #11 10-22-2003, 07:02 PM

I got a new radiator for a total of $193 and finally got a around to putting it in. Put it all together started it and it runs a tad bit cooler but is still running hotter than it used to (still pushing 95C). I am going to drive it over to the shop I got the radiator at and let them take a look at it.

Chris

kerry · #12 10-22-2003, 08:25 PM

Have you tested the fan clutch?

Gurkha · #13 10-22-2003, 11:43 PM

Have you checked your temperature sender which is attached to your engine block? Sometimes it malfunctions and sends the wrong temp to the gauge. Happened to me with a brand new OM 616 where the temp would regularly hover around the upper 90 mark and yet everything was working fine. Changed the sender and everything went back to normal.

chrisalex78 · #14 10-23-2003, 04:05 PM

Took the car to the shop I got the radiator from. The guy checked the temp right by the sending unit and compared it to the gauge. He says the sending unit or something with the gauge is wrong because it is not running as hot as the temp the gauge shows it is running. Guess i am going to start messing with that know, thanks for the advice and replys.

Chris

Gurkha · #15 10-23-2003, 10:33 PM

Thought so, the diesel guage as well as the temp gauge from VDO are really problematic, could never get the fuel gauge on my 240D to work. The temp gauge isue is really an annoyance as it would unneccesarily scare one even thogh it is a false alarm.