300SD overheating-again. - PeachParts Mercedes-Benz Forum

RG5384 · #1 06-12-2003, 09:58 PM

Tried the search, no real results. On the way home from work tonight i noticed that my temp on the interstate had gone up to about 115 with the a/c on. I promptly turned the a/c off and the heat on, and it slowly went back down to about 105. It stayed at around 105 untill i got to my apartment. I then went to go get food, and in the drive through line the temp would crawl up as soon as i put on the a/c, and drop immediately if i would bump the throttle up to about 1500rpm. Also, going 20mph through the back of the parking lot with the a/c on yeilded a picture perfect temp of 82. I'm confused as to why it would overheat on the interstate(lots of airflow) and not going a measely 20mph. The thermostat was replaced about a month ago due to the temp always being at 100, the new thermostat did not change that, and according to a infared temp gun the temps were in spec so i did not worry about it. Also, the radiator was replaced about 1 1/2 years ago. The aux electric fan is working. I should also note that i heard a slight bearing noise at idle, and it goes away as soon as you tap the accelerator. This could be my air cleaner bracket as well though, as it is currently broke. I have had no chance to check water level, or look for leaks, but based on the symptoms alone what does this sound like to you guys? I'm hoping to go back home to tampa for the weekend, but dont want to take an overheating benz. Thanks in advance,
Ryan

Fisherman · #2 06-12-2003, 11:07 PM

Have you checked your main fan for correct operation? There's a lot of info here but if you can spin it by hand and it turns wihtout any resistance then it's toast...

psfred · #3 06-12-2003, 11:14 PM

Ryan:

The visco clutch should lock up at a coolant temp of 95 or so -- you should hear considerably more fan noise and feel a lot more air.

The quick way to test is to let it idle and get hot -- you may need to block the rad so no air gets through, or very little -- and the fan should speed up at about 95. Or you can stop sometime when it is too hot and have someone else shut the engine off while you watch the fan. It must stop within one revolution of when the engine stops. If it spins more, the clutch is bad.

If they didn't cost so much, I'd just tell you to change it, but you may want to know it is bad first.

Do also check the coolant level and make sure you have a good radiator cap -- they go bad and fail to seal, so you have no pressure and the temp starts to climb. When hot, the hoses should be hard (be carefull, they will also be hot enough to burn!)

Peter

RG5384 · #4 06-13-2003, 12:01 AM

i think you might be on to something with the radiator cap idea peter. Both hoses were soft to the touch at idle(and very hot). I'll look at the radiator cap tomarrow. I'm glad to see that neither of you suspect the water pump as of yet, that has me a little concerned due to the price of replacements.
Ryan

billrok · #5 06-13-2003, 12:57 AM

Your problem is not your water pump unless its leaking. But don't worry if you ever need one. They are about $25 from the Dealer. Probably the easiest water pump to change and the cheapest in the world.

73MB280SEL · #6 06-13-2003, 05:26 AM

I'll just throw this out: I've heard that older water pumps can have eroded blades so that they won't move the required volume of water through the system. Maybe checking out the water pump wouldn't be a bad idea.

Sholin

RG5384 · #7 06-13-2003, 08:41 AM

she was a little low on water, and the viscous fan was hitting the plastic surround. Both problems have been fixed now, so i guess i'll just see what happens. Thanks for the help guys, i'll let ya know if she makes it or not.
Ryan

RG5384 · #8 06-13-2003, 02:57 PM

well, i made it home(barely). The entire way on the interstate the temp did fine, even with the a/c on and a traffic jam for about a half hour. However, as soon as i got off the interstate it started to try to overheat again. What makes no sense is why it didn't overheat on the interstate when i was stuck in the traffic jam. Another problem also came up, my starter is now shot. I stopped to grab food, and when i came out the car would not start. I tried jumping the ignition switch etc by using the terminals on the passenger wheel well, and that still didn't work. I had to bang the cylinoid with a broom stick for five minutes and then it turned over just fine. I'm beginning to hate this car. Thanks for all the suggestions, i'll let you know what it turns out to be.
Ryan

Thomaspin · #9 06-13-2003, 05:10 PM

Ryan - it's not too hard to replace the solenoid - the starter is heavy and you will have to remove it first - I describe this on my site. I replaced mine with a rewound unit and it works great. Inexpensive. No need to replace the whole starter.

Your overheating problem is intriguing and I would be interested to learn the fix. It does not sound like the freeway/no freeway issue is relevant based on your description. Could it be that your thermostat is getting stuck (just because it's new is no guarantee of function), with the freeway/no freeway issue just a coincidence? Is your temperature sensor sound?

Your car has another good 160k of life left - love it a bit and it will earn your respect, especially given how much work you have already put into it.

leathermang · #10 06-13-2003, 07:33 PM

While some of the symptoms don't fit exactly.... you need to check your lower radiator hose.. It must not be able to close... it should have a spring in it which keeps it from restricting flow when water pump flow is high....squeeze it.. if it will squeeze , replace it.... that may not be all that is wrong, but it may be one of the things....

RG5384 · #11 06-13-2003, 07:34 PM

I was thinking the same thing with regard to the thermostat. I'm going to flush the entire cooling system thoroughly this weekend, and when i'm doing that put the t-stat in boiling water and watch how it reacts. Do you have a part source for just replacing the solenoid? How much was it? For now i'm putting a broom handle in the trunk, i do not have the time this weekend to mess with it, plus i have free towing on my phone so once it's back up in jacksonville i can always get it towed to my apartment for free. I looked at the write up on your page for the starter(found it when i did a search), thats a great write up and will come very much in handy. Do you recall the time it took you to fix it? If its only a couple hour job i'll probably do it right away. Thanks again,
Ryan

vwbuge · #12 06-14-2003, 12:01 AM

Billrok is wrong, 73MB is right. I've seen a few cars that, when at idle the temp would rise. At higher engine speed temp would drop. Upon inspection of the non-leaking water pump, I found eroded blades inside the water pump. If all the other components of your system look good and the level is fine......change the water pump. It is an easy, inexpensive, D-I-Y fix!!!!!!

RG5384 · #13 06-14-2003, 12:50 PM

flushing the radiator out had a minimal effect. I now beleive it's the water pump, as nothing else makes any sense. My dad and i are talking about possibly just getting rid of the car, in favor of a newer more "sporty" type car that i would like alot more, and hopefully be more reliable. As it sits, the car has an overheating problem, starter problem, track rods are gone, needs new rear tires, drivers side door lock is broken, electric locks broken, drivers window broken. Plus's are the a/c blows cold and works well(fully automatic etc), has newer style seats in the front, dash with only two very small cracks, new alternator, fairly new radiator, new front tires, four new bilstein shocks, engine starts/runs great(when the starter works), tranny shifts perfect despite being original. If we did decide to sell the car what do you think we could get for it? Trying to keep all options open, and as we are seeing it it would probably take a grand to get back into perfect mechanical condition. All thoughts appreciated, including other car possibilities.
thanks,
Ryan

Thomaspin · #14 06-14-2003, 01:34 PM

Toughest bit is removing the starter, as it's fairly inaccessible, but a bit of front wheel turning will get you there. Just nuts and bolts. No special tools.

The solenoid bolts to the starter. I took it to a starter place - nothing unique to this generic Bosch starter solenoid. They had several rewound ones in stock. Cheap core trade.

Your choice would appear to be to put $1,000 into the car and have many more enjoyable miles, or get something '...more sporty....' with a host of new, to-be-discovered problems and, presumably, negative cash flow on the trade. Plus you write-off all your sweat equity. What's your time worth?

RG5384 · #15 06-14-2003, 02:06 PM

I think the main thing is that i'm completely burnt out of the car. I have no desire to fix it up any more, no desire to fix it, i'm just plain spent. An 83 mercedes diesel isn't exactly a 19 year old's choice car, and the fact that these things keep coming up makes me really dislike it. I think it might be time to move on to something else. The car would be a great fixer up project car, but i need a reliable daily driver right now, and this car is seemingly not up to that task in it's current state of repair. I don't think anyone would argue that a newer model acura integra wouldn't be more reliable, and i'd probably have more fun with the car too. I think we've decided on ordering and replacing the water pump, and just keeping a broom handle in the trunk for the starter. Thanks for everyone's help, i'll let you know what we decide to do.
Ryan