Thermostat confusion! EPC and FSM conflict - PeachParts Mercedes-Benz Forum

Shortsguy1 · #1 04-03-2013, 01:02 PM

Hi-
My little 220D OM615 tends to overheat on hills. I am trying to figure out why, but in small baby steps. I want to change the thermostat and cannot figure out which one to buy: 80C or 87C.

The FSM (20-005) for the OM615 says to use a thermostat "that begins to open at 80C."

When I put my VIN into the EPC, the only thermostat listed is the 87C version. Also, while I unfortunately have not found our sponsor's website to be a reliable source of information, Pelican only lists the 87C thermostat for my car. But if I put in a late 1970s 240D, Pelican does carry the 80C version, but are simply claiming it is not right for my car.

So what would you do, in the context of a old car that tends to overheat? Follow the advice of the FSM (=80C) or follow the advice of EPC/PelicanParts (=87C)?

Thanks in advance!

lorainfurniture · #2 04-03-2013, 01:11 PM

Perhaps you are reading in to it too much. Maybe it begins to open at 80, and is fully open at 87?

Either way, the slight overheating will not be solved by the lower thermostat. They will both be wide open at 87. Your engine will just have a lower running temp.

I would try doing a rad flush, and check the fan clutch if it has one (sorry, im a w124 gas type of guy)

martureo · #3 04-03-2013, 01:44 PM

Quote:

Originally Posted by Shortsguy1

Hi-
My little 220D OM615 tends to overheat on hills. I am trying to figure out why, but in small baby steps. I want to change the thermostat and cannot figure out which one to buy: 80C or 87C.

The FSM (20-005) for the OM615 says to use a thermostat "that begins to open at 80C."

When I put my VIN into the EPC, the only thermostat listed is the 87C version. Also, while I unfortunately have not found our sponsor's website to be a reliable source of information, Pelican only lists the 87C thermostat for my car. But if I put in a late 1970s 240D, Pelican does carry the 80C version, but are simply claiming it is not right for my car.

So what would you do, in the context of a old car that tends to overheat? Follow the advice of the FSM (=80C) or follow the advice of EPC/PelicanParts (=87C)?

Thanks in advance!

I'd be worried about more than just a thermostat. Yes, the thermostat is the lynchpin in the cooling system, but other parts will contribute to the overheating.

The radiator. How old is the radiator? Has it ever been flushed? Are there large portions of mashed down fins? Are the fins filled with dirt/grime/sand/small animals/bugs?

The hoses. Are all hoses leak free? Are any kinked/smaller than they should be?

The engine block. Is there rust on the internal passages? Have you ever drained the engine through the plugs and flushed it? It's not probable, but there might be something blocking a passage internally.

The fluid Are you using MB fluid? Or Zerex? How old is it? What ratio are you using?

The 87°C thermostat shouldn't be that much of a difference from the 80° one. Personally, I'd try the 80°C one first to see if it fit. If not, then I'd go to the 87°C version. But I think you might have other problems to consider first.

EDIT: Oh yeah, lorain is right, check the fan clutch as well.

Shortsguy1 · #4 04-03-2013, 02:04 PM

Those are all great suggestions. Car had green coolant, but now has zerex as of a year ago (when I got the car). I used a commercially available flush liquid (Prestone?), as I hadn't heard about the citric acid flush at the time. I flushed the engine and radiator and lots of rusty colored water came out of the engine. I am using an estimated 50/50 mix for the coolant. Hoses are all new. No leaks. I don't know the age of the radiator. It does need to be cleaned of a few bugs, which is one of the many steps I plan to take. But its physical condition is fine. I just got the electric supplemental fan working again, so that should help a little. I didn't use the plugs to flush it, but hooked up a hose to push liquid through.

I actually don't know if the car has a fan clutch or not. That is one of the things I still need to figure out. Stupid question, but if the fan spins when I give it a twirl with my hand, does that mean it has a clutch? The EPC suggests that my car didn't have one when new, but I am not sure right now.

So some progress has already been made in this area, but there are still a few other things to check. Thanks for suggestions. I really appreciate the help.

toomany MBZ · #5 04-03-2013, 02:55 PM

I believe if the fan spins by hand, it has a clutch.

t walgamuth · #6 04-03-2013, 04:27 PM

When you say it is overheating what do you mean specifically? It is quite normal for the temp to rise and go back down after the hill. Question is how much does it rise?

Shortsguy1 · #7 04-03-2013, 04:50 PM

Sorry, I should have been more clear about that. My temp gauge is in F. It has indicated temps at 175F and 250F, and a little dash between, which I assume is to indicate 212F. On a moderate day (70F) while driving up a 5-6% grade for a few miles at 60 mph, the temp will rise and rise and rise until it would hit the red mark at 250F. I obviously don't want that to happen, so I get on the shoulder and drive up the hill at 30-40 mph, where I can keep the temp below red (250), but still incredibly high. I don't recall exactly, but I would guess 230-240F. I have never actually had the car boil over and as soon as I reach the crest, the temp drops back down again quickly. I hate having to drive on the shoulder of a freeway because my car is at risk of boiling over. A 220D is slow enough up hills as it is, I shouldn't have to intentionally drive the car even slower.

As an aside, the valves for the interior heat are stuck and do not allow me to easily turn on the heat inside the car as a preventative action.

Any other thoughts are appreciated.

Shortsguy1 · #8 04-03-2013, 11:56 PM

Tom W.-
As a slight aside, I followed your advice in post 25 of this thread on removing thermostat bolts:
http://www.peachparts.com/shopforum/diesel-discussion/323311-poll-who-has-broken-616-617-thermostat-housing-bolts-2.html

and it worked out great. I was scared to tackle this a year ago when I changed out the coolant and hoses, but by taking it slowly and going back and forth slightly each time (with lots of PB blaster), all four bolts came loose. (On my car, there are four bolts and they all face up, so access is a little better than for some of you.) Anyway, thanks for the helpful advice.

I don't actually have the new thermostat, so I just cleaned the bolts, put anti-seize on them, and closed it back up. But once I order my new thermostat (80C probably), it will be a 10 minute job. Whoohooo!

Govert · #9 04-04-2013, 05:22 AM

The 200D will not have a fan clutch. The fan will not affect cooling if you drive at speed, it is only useful when driving slowly.

During hill climbing and driving at full load at speed, the temperature can rise to about 100 degrees C (212 F). Slow mountain climbing in low gear never increased the temperature on my 200D.

There are two thermostats for the 200D, depending on the engine. Old engine (55HP) up to and including February 1979 A6162000415; New engine (60 HP) from March 1979 A6172001815. Both are 80 degrees C thermostats. Are you sure you entered the VIN/Chassis number correctly? The 87 degree thermostat is for gassers.

t walgamuth · #10 04-04-2013, 06:24 AM

250 is of course too high, but if you have never boiled over and it always comes back down I would tend to suspect the temp guage is not reading accurately. If it is an electrical guage, I know the 115 chassis is known for having ground issues on the instrument cluster. Ground issues can frequently cause gauges to act goofy. Perhaps someone will have a better thought on verifying its function.

Shortsguy1 · #11 04-04-2013, 10:17 PM

Govert-
My car is actually a 220D. I revisited the EPC, and it definitely had a fan clutch on the car originally. According to EPC, 115.110 cars after 208608 got the four bladed, no clutch version. My car is 020696, so it is an early one and got the clutch with a metal 8 bladed fan. It is funny that the put clutches on the first 220Ds, and then did away with them for a while.

I tend to trust German engineers, so I wonder what led them to stop using fan clutches on the 220D cars? Perhaps I should follow their lead?

Based on all the great suggestions, I plan to go with the 80C thermostat. I also will double check that I don't have a bubble of air in my system. I am pretty sure I burped it well by filling the engine the inlet and outlet, but you never know. If none of that helps, I will then verify that the temp indicator is correct.

Thanks all. When I get it all swapped out, I will update this thread.

t walgamuth · #12 04-04-2013, 11:20 PM

I imagine they did the math and found the clutch didn't pencil out as an energy saving device on the 240. When on the highway the fan is basically being pushed by the air so it doesn't cost much energy to turn it, and the fan clutch is heavy and the big emphasis on the 240 is light weight. or 220.