Max engine temp under load - Page 2 - PeachParts Mercedes-Benz Forum

gsxr · #1 06-05-2002, 04:39 PM

Mike, be sure you separate the responses from people with a different engine than yours. Anecdotal sub-105C temp numbers from an OM617 are 100% useless to you (and me, and HGV). The OM60x are totally different animals and will run hotter than the old iron-head beasts. But I'm sure you already know this.

I'm surprised your car went up to 120C, that is quite high, for only a 4-mile stretch. What was the ambient temperature? Have you cleaned out your radiator AND condensor so they are bug- and debris-free? Otherwise, as I mentioned on the diesel list, use a bottle of WaterWetter (if you're not already), and if your fan clutch is original (metal blade) I'd seriously think about replacing it as a preventive/predictave maintenance item.

The rest of my previous email still stands, i.e. if the car never goes above 105C under ANY other conditions, I wouldn't worry too much. But I'd still check out the fan clutch. I'd love to hear your resuts if you do replace it. Maybe try "forcing" it on, like someone else did (wiring it to the pulley somehow)??

Good luck,

msyoder · #2 06-05-2002, 07:15 PM

Dave,

I have noted the different behavoirs of the two engines and filtered accordingly. I will definatly be testing the visco fan clutch and clogged air flow in the rad. Probably not until this weekend, though.

Yes, it definately went to 120 deg indicated. It was warm and humid. The external temp was showing 90degF, but it behaved likewise (though less extreme) on the way home and the temp was in the 70s.

It was Jim Cathey that wired his fan. He seemed to have the most promising anecdote if he was crossing the Rockies at highway speed.

I'll post the outcome as soon as I have more to share. Thanks,

#3 06-05-2002, 09:34 PM

OK, I'll weigh in on this thread. Since the temps have summered in Tennessee, I have seen my new to me 1987 300D get pretty warm.

Driving down the interstate with the ambient temp at 95F, when hot soaked, my indicated temp is about 95-98C. With a steep grade, it will range to about 105C and return to 95-98C on the flat pretty quickly.

If I get off of the interstate and shut the car off. When re-started it will indicate about 115C for a very short time and immediately begin to moderate as the car moves, even at low speeds.

I have replaced the thermostat with no change in behavior. I have determined (at least to my own satisfaction) that my Visco fan clutch is a non-performing asset. It does not change speed with the engine, regardless of indicated temp and has absolutely no drag on it at idle, again, regardless of the temp.

I have purchased a used Visco fan clutch from PGAuto and will install it sometime this week. I will report my experience here.

One thing that I do find interesting, is that the car does manage to keep itself below about 115C. I can only surmise that the auxillary fan is responsible for this. If I let the car idle from a cold state in the driveway, the aux fan will begin to come on well below 100C. I guess, as the demand for AC lessens due to the interior of the car getting near the required temp set by the climate control, the "coincidental" aux fan help goes away. This is how I explain the fact that the car will go to 115C when coming to a stop after a long hot soak. The aux fan must be coming on because of temp at some point, which is keeping the temp from running away.

Ambient temp seems to make a huge difference. At 80F ambient, the car rarely goes over 90C, and then for very short times.

If I see the temp going up (which I watch closer than the speedometer these days) I can bring it down quicky by punching the defrost button and spinning the wheel to max. This can be uncomfortable for a time.

As I said, the fan clutch is next and I'll let you know. Comments and suggestions are welcome...

BR,

Steve (8C>

gsxr · #4 06-05-2002, 09:57 PM

Steve,

What you describe is eerily similar to what I saw when I bought my first 1987 300D a few years ago. It should not get to 115C at idle - period. If that 115C is only after shutdown, hot soak, and restart, that might be OK, but never 115C without a shutdown involved! If it does get to 115C at idle, it's not the fan clutch, it's the radiator. Swap the clutch first since you already have a "spare", albeit an unknown good one.

FYI, the electric fan runs on low speed when the R12 pressure exceed ~22 bar (?) and kicks on high when coolant temp exceeds 105C.

I'm assuming you have already flushed the cooling system, used fresh MB coolant, and hopefully a bottle of RedLine Water Wetter? On a different note, the plastic reservoir tank was updated twice. The latest part number includes a silica pack inside to help control corrision with the iron block & aluminum head. The new tank from online vendors is ~$40.

These radiators are known to have a tendency to plug or corrode internally in a short time, possibly in 2-4 years (mine did)! The flow is fine, as viewed with a hose stuck in one end and watching the outflow, it just doesn't transfer heat well. This makes it a real PITA to troubleshoot. BT, DT. A new one is $225-$325 (Nissens vs. Behr), or you can have yours rebuilt by Reseda Radiator for ~$125 plus S&H both ways. Any of the above are fine IMO, but be warned the Nissins doesn't have the metal reinforced necks, and your original won't either (unless it's been replaced in the past).

Both of my '87's, and my sisters, have recently rebuilt/replaced radiators. All 3 now refuse to get over 100-105C under any operation conditions (but we don't have any REALLY long, steep grades to test on like Mike does.) Climbing to Reno from Sacramento up the Sierra Nevada mountains still won't get it over 100-105C tops, and that's at 70-80mph up the grades with the AC on.

We had temps to 104F here today. I drove the car with the AC on max, and even standing on the throttle a lot to accelerate it wouldn't get over 100C. Mostly ran between 90-100C (90C steady on the freeway, 95C at idle, up to 100C under load).

HTH,

JimSmith · #5 06-05-2002, 11:02 PM

Well, here is another try at the scanned images from the manual. I will try the schematic of the system, then two sketches of the thermostat, and some text. Jim

JimSmith · #6 06-05-2002, 11:06 PM

Here is the thermostat under initial conditions, before it starts to open. Jim

JimSmith · #7 06-05-2002, 11:09 PM

Here is the thermostat in the normal or part load condition. It is possible for a thermostat to get stuck in this position and let too much flow short circuit the radiator path, leading to over heating. Sorry about flipping the figures sideways, but it was the best compromise to get decent resolution. Jim

JimSmith · #8 06-05-2002, 11:14 PM

Under full load the path under the thermostat from the engine ("d") gets fully blocked off and forces all the flow to the radiator. In a properly functioning Diesel I have never seen this condition not keep up with the heat load. Especially at idle as a Diesel at idle will hardly reject enough heat to the coolant in the winter to keep the engine warm, or the heater functioning effectively for the cabin. Here is some additional text from the manual, which suggests the operator should not get too antsy about excursions to the higher temperatures in certain conditions. Jim

#9 06-05-2002, 11:20 PM

Thanks Dave,

I have read most of your posts from the archives. The pics of the cracked head a really scarry, which is, in part, why I am so diligently seeking lower temps.

I certainly would not want to take issue with your statement about the radiator. It will probably have to be replaced. But, as you said, it is a PITA to diagnose and the fan was a no brainer. This coupled with the fact that I could try the fan for $60 with a 100 day warranty made this my first step.

BTW, I have checked the top hose for pressure overnight, none, thank God. And I have checked for signs of coolant/oil co-mingling, also negative. I could almost see this going through your mind as you composed you post, and rightly so.

I will get to the bottom of this and solve it. I have driven Mercedes in my business since 1993. I average about 5000 miles per month. I have always bought gas cars (recently V8s) with 100,000 miles and clocked them out. This 300D is a experiment for me. I have been buying cards for $16m to 20m, driving them for 200,000 miles and selling them for $6m to $8m 3-1/2 to 4 years later.

I have fallen for the 124 diesel in a big way and hope to bring this '87 to top shape and then continue to repair it, indefinately. Even to the point of replacing the engine, whenever it becomes necessary. It all boils down to dollars/mile for me. If I can be successful at getting into a reliable car with necessary repairs for $5m to $6m (I'm currently still under $4m in this car) and then spend another $5m per annum to keep it up, I have achieved a lower cost per mile than is possible when depreciation has to be factored into the equation.

This car may have higher maintenence costs than my typical ride but the depreiciation dollars have already been paid by the PO.

I appreciate your comments and I will keep you informed of progress.

BR,

Steve (8C>

JohnM · #10 06-06-2002, 12:38 AM

Jim,

Thanks for posting the pictures. I haven't broken down and bought the manuals yet so this is a big help.

John

gsxr · #11 06-06-2002, 01:19 AM

Hey Steve,

If you've never replaced the fan clutch on a W124.133 (or .193), it's NOT easy. If you don't have the two special tools I **highly** recommend pulling the radiator. This will also allow you to clean the radiator fins, and condensor fins, thoroughly while it's out. Also a good time to inspect the serp drive belt and tensioner (tends to fail every 50-100kmi - must be perfectly parallel, if angled at all, replace ASAP). Clean up the face of the clutch & flat bimetal spring before installing. DO NOT remove, bend, deform, or otherwise mess with the flat diamond-shaped spring, you will ruin the clutch!!!

With the special tools you can R&R the clutch in 5 minutes with the rad installed, without the tools plan on 30-60 minutes, lots of French, and skinned knuckles. They tools needed are:

Short, stubby 8mm hex socket tool (3/8 drive) - cheap, ~$5-10 from dealer??
Spinner tool to spin the bolt out (hard to describe - I should take a picture of the one I made for ~$5, instead of spending $50-75 for the MB tool)
Serp belt holding tool so you can torque the bolt on & off (NOT cheap - $50-$90)

If you're interested I might be able to take photos, and/or get part numbers.

Have fun!

HGV · #12 06-06-2002, 01:58 PM

The 603 series engine has a different cooling system than the 5 and 4 cylinder ones. It has a by-pass function on the t-stat that recircs hot coolant through the block until it completely closes at 100 deg C. Then it runs 100% coolant from the radiator. I take this as the design intent is to have the engine run somewhere between the beginning opening temp of the t-stat of 80deg. C to the fully open position of 100 dec. C. (no bypass). Does anyone have an idea what the temp rise through the engine should be? Also if you are interested I have a brand new in the box radiator for a 87 300TD. I ran it for two hours and realized that my old radiator was fine. It is a Behr and in new condition with all the protective caps installed.

Henry

#13 06-06-2002, 05:27 PM

Hi Henry,
I would definately be interested. Please contact me off line at sschweg@concentric.net. If you will give me your phone number, I will be happy to call you.

BR,

Steve (8C>

msyoder · #14 06-10-2002, 08:35 PM

Saturday I drove to CT and the engin temps under way were perfect. The air was cool, (60s) and the eng. temp was 85 deg. Couldn't make it budge 'til I got back to traffic in NYC.

When I returned I did the roar test. There was some roaring above 3000 rmps, but I was not impressed. I did not hear the roaring subside at the upper RPM limit. In addition the fan freely spun when the engine shut of. I read and it seems logical that if it is tightly engaged it will stop more abruptly. All this happend at 100 deg and slightly above. It is also the original metal blade type.

Does anyone think I'm wasting my time and money to replace this clutch?

Steve, did you replace your fan yet? I plan on getting mine done next Sat. I'm eager to hear if it makes a difference.

#15 06-10-2002, 08:39 PM

OK... I replaced my fan clutch and now my temperature guage is broke...

In truth, I'd rather be lucky than good

.

Seriously, I had a buddy help me and we replaced the fan clutch. You're right Dave, PITA

. Anyway, this morning I headed for the Saturn plant in SpringHill, about 1 hour form the house. The ambient temp was about 85F. The car never got over 90C despite some.. uh... spirited driving.

When I got to SpingHill, it was lunchtime, so I locked the car with my spare key and let it idle while I went in and got a sandwich. I came back out and let it idle with the AC on COOL while I ate my lunch.

It never got over 100C. In fact, when moving at, say 30mph, it wanted to run at about 85C.

I left there about 4:00pm with the ambient temp about 92F. I drove it hard back to town and stopped for fuel when I got back. I shut off the car and fueled, restarted and entered stop and go local traffic for about 20 minutes. Never got over 100C

.

I think I am going to declare that the fan was the problem.

Thanks for all of the feedback. I will take the long grades next week, but I'm pretty confident. It's like a different car altogether!

BR,

Steve (8C>