Expensive fan clutch. Is modification possible?
 

My 87 300d with 603 eng has a bad fan clutch, it just spins and spins after shut down when its hot even at 100deg eng temp. I have the aux fan running strait in the mean time but the clutch is over $200 new which I think is the only long time solution as opposed to injecting it with toyota fluid. I went to Strauss the other day and all the fan clutches they had were between $30-$40 while my 603 clutch is over $200 which is rediculous. I was wondering if is possible to swap a fan from another car, MB or otherwise, or maybe even converting to an electric main fan altogether using a fan from a pull-it-yourself yard and the relay and sensor from the same car(many of them even have 2 speeds) but I would buy the relay new and change the bearings on the new (old) fan. I dont see what's so special about these 603 fan clutch that makes them so expensive, its really disheartening having to pay so much for a part that is at least 100% cheaper on must every other car which is what makes me think of doing this swap. Has anybody else try something like this?

Neil/kdj??? who dropped a C36 engine in his 300TE swapped the clutch fan for a SPAL electric fan. SPAL makes good fans and such a swap is not done to save money.

Dave/gsxr will advise you to upgrade your alternator if you swap the clutch fan for an electric fan. Fortunately used 143-150 amp fans from W140s and R129s are reasonably priced at around $100 and are an easy conversion. You have to swap in the 603 alternator pulley and run a big fat battery wire in place of the skinny 603 wire.

Sixto
95 S420
87 300SDL

hi there, just read your thread and guess what? i just went over the exact same problem you have......didnt want to crack for the expensive new clutch.
so i went to the self serve yard after taking some careful measurements,and found that with very minor modifications that for my 1980 300d a fan AND clutch from any mazda or mistubishi truck just about bolts right in. i did this yesterday and it works great...also alot quieter then having a directly bolted on fan(which i had before) .....the diam for the fan blades themselves were only about 1/2 inch smaller on these trucks,i was going to try and use my old fan and modify the clutch but surprise surprise, didnt even need to do that.
the only two small mods were: had to slightly enlarge the bolt holes on the hub itself,pattern was the same but holes were a little smaller. and the 2nd,
since i used the fan from the mitsubishi truck, the blade pitch was slightly greater,and it was just catching the crank pully and ticking a little (the blades are plastic) i filed them down just a tad, and now it works great!!!!!
both mods took a grand totoal of 5 minutes :sun_smile :sun_smile :sun_smile hope this helps

Mbonly, don't know if it would fit, but I have a used (150Kmiles) fan clutch from a 1986 190D 2.5 for $40 shipped to your door in USA. Believe is a 602.911 or 912 engine. I would have to figure out how to test it before shipping.

I have never done this, but I have read that there is a pin that is actuated by a bimetallic spring. This pin is what locks up the fan when hot. You can somehow drive this pin into place to permanently lock the fan clutch.

Do some searching here because I know that there is a thread or two that explains this in detail.

Good luck,

the seach function is a wonderful thing.................
 

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http://www.peachparts.com/shopforum/showthread.php?t=127621&highlight=fan+clutch


If it were me, I wouldn't be buying a new clutch very soon. ;)

That's great, I actually own a mazda B2600i that I redid the head my self so is very familiar to me, thanks for the info.

I'll do some searches to see if its the same, I appreciate the offer.

I though about doing something like that but the only problem is the noise and then having to probably undo during the winter but as far as cooling goes it'll probably work great!!!!!!!!!

you could
 

also probably put on a rigid 240 fan. also i think you can take out the clutch assembly an d insert a spacer that bolts on rigidly. in fact i think i have such a device (universal) in my garage somewhere that i never installed.

That's interesting, for $200+ we shouldn't be worring about whether or not it will work. Its interesting that my Mazda B2600i when I start it in the morning the clutch is still engaged and you hear it roar for a few seconds and then it goes silent but when it is hot you definitely hear the fan and is no coinsidence that this little truck never goes pass 1/3 of the scale regardless of the temp outside even with 170K miles. I had cooling problems in my sd also but it wasn't as critical as in the 603 for just one overheating event and I'm out 2 grand, and will be looking for 2 #17 heads as opposed to one since my other 300d is down with a cracked head. I'm beginning to believe what others have voiced in this forum which is that our diesels were designed with picky and sensitive cooling systems or maybe we just get too confortable with the durability of our cars. I do have to admit that my fan is the original with the metal blades and is been there for 18 years and 244K miles.

Larry sugested the same thing, do you have to take them out during the winter? I assume a rigidly mounted fan will affect winter operation somewhat.

no
 

i wouldnt think you would have anydifficulty in winter. assuming you have a thermostat. the rigid fan will just cut your mileage a little and take away a little power.

I agree that these cooling systems are not of sufficient capacity to handle a heavy boost load from the 603 in high ambient conditions. Yesterday, mine was running to 100°C. on every uphill climb that lasted 15 seconds or more. In heavy stop and go traffic, same deal......right up to 100°C.

But, I'm quite convinced that there is nothing to be concerned about, provided it does not exceed 110°C. I've never seen it that high, but, I do believe that it will get there under more extreme conditions such as a 10 mile upgrade in 90°F. ambients. But, this is why you have a gauge. If it climbs that high, you can control the temperature, almost instantly, by lifting your right foot. Take the boost away and the temp will drop back to 90°C. within about 90 seconds, even with the a/c running.

Additionally, make sure that the auxiliary fan is working and that it will engage at the design temp. of 105°C. Of course, this is a difficult check to make. It's not easy to get the engine over 105°C. to confirm this. You might need to cover the radiator to do it.

sounds
 

as if putting in a rad with an extra row of cooling tubes might be a good idea. but i have not had this prob with mine.

You're right, Brian. The extremes of high ambient temps and heavy engine loading on an uphill grade are where a more efficient radiator would be helpful. Several years a go I heard of a rad shop in Sun Valley, CA that had made up a three row core for the 617 turbodiesel (123 chassis). It looks like a Behr on the front and back and has the infamous black plastic tanks. It was $229 out the door, so I ordered one and drove down to get it. The place never made any more of them, saying they were too much trouble and not enough profit or something. That baby does wonders, for example I can hit the Grapevine (I5 into So Cal from the southern end of the San Joaquin Valley) mid day in the Summer with a lot of stuff in the car and AC on and the engine never goes over 100. In fact as long as I can keep rolling over 50 or so my gauge stays around 95. Some dork changing lanes might throw me off and the trans downshifts and it will just barely see 99. I think I've seen 100 on I17 into Scotts Valley on a long uphill slope w/ slow traffic.
I wish I had the same performance on my '87 300Dt. That may not be possible in the same volume (area actually) because of the additional heat loading the aluminum head seems to generate. I know! its not the head that generates the heat, but it efficiently transfers therms to the coolant, besides the engine has more HP available for one thing. Thermal management stuff is fairly complex (and not my field!) it all "boils down to" (sorry for pun) the fact that the 603's run hot! The later 603 fans (according to gsxr) are plastic and the thermo clutch is different to let the engine intentionally run hotter for lower emissions. Shame on MB! So using a lower temp (grey) thermo switch is in the right direction but upgrading to a later fan is not, unless I am missing something.

Some 'Forum member ordered a custom three row radiator made out of all aluminum, welded tank an all, that would be nice to have for these engines. Maybe a search would locate the shop but be forwarned, its not cheap!

right on, walgamuth. I suspect the reason you haven't seen those conditions is because you never have to drive the conditions I described previously, ie. in the mountains on long winding roads. Count yourself lucky! I have been switching AC off when I have to drive uphill like that here on a Summer day, and get behind a slow moving car. I have to baby my #14 head! :(
Besides, we have been seeing more than normal amount of hot weather here this season!

This is really the defining test. Most all of us in the east don't have a situation where the engine is in heavy boost for more than four to five minutes, maximum.

When you need to run the engine in boost for 15 minutes at ambients above 90°F., I'm quite sure that no stock 603 is up to this task, if the temperature of 110°C. is considered the maximum acceptable temperature.

In such conditions, a larger radiator is almost a necessity, IMHO, unless you are OK with driving those hills at 40-45 mph with the boost off.

Of course, you could follow the owner's manual and run the engine up to the limit of 119°C., in theory. :eek:

Just to update everyone, I installed another new clutch fan only to discover that there was no difference from the first new clutch fan. I even doubt now that there was anything wrong with the old clutch fan?

It's been over 90 degrees for several days where I am, and with the A/C on, sitting in traffic, the temp guage has yet to get more than a smidgen over 100c, and it cools right back down to between 85c and 90c, once I get through the traffic, and rolling again! :)

And, I take it, the new fan does not engage whatsoever at these temperatures?

As an aside, have you ever seen the auxiliary fan engage (engine above 105°C.)?

Ya, I did see it engage when I tested running the engine to what the guage showed to be approx 110c. It does work!

I give up!

But you know Brian, it's really not having an overheat problem despite my attempts to hopefully prevent such with these new clutch fans. Maybe the fan kicks in at 115c ??? Or, maybe there is a blockage in the radiator in front of the clutch fan? The only way to know for sure is to use a electronic thermo gun to check temps!

Man I'm so lost on if my clutch is bad now or not on the SDL. :D I do know it was replaced as it has the plastic fan currently...

Does anyone have a brief overview on how to remove it to see which brand I have in there? :confused:

I know mercedes marketed this vehicles worldwide, I wonder if they kept the same specs for cars destined for lest say the middle east or a country with desert conditions. If they did, It'll be interesting to see what they do overthere to keep them running under 120deg.

i am pretty
 

sure that you can order rads with an extra row of tubes from rebuild places. if you cant find a source let me know and i will ask my machinist where he got his.

diehard, I can charge the SDL up the Sunol and Adrade grades on the hottest day with the AC running. I haven't been to the Sierras but it took the grapevine and lots of idiot random lane changers to hit 105 with the AC on.

Sixto
95 S420
87 300SDL

There's a thread in the tech help section about a tropical clutch kit. From what I remember US parts systems don't recognize the part number. It might be an aftermarket part rather than an OE part. Do you know someone in Singapore?

Sixto
95 S420
87 300SDL

Assuming water pumps are basically alike, would it be possible to overdrive the 603 water pump? I mean a 103 water pump is good to 6000 rpm or so. If MB didn't think of it, a 15% smaller pulley (if my math is right) should keep the water pump in an efficient range. Might need some flow tests to know for sure.

Sixto
95 S420
87 300SDL

just
 

me being intuitive, but i doubt that the water pump is the weak link. more radiator seems to be the way to go in my minnd. your thinking is correct in the abstract, but if a pump is spun more than its max optimal speed it will cavitate and all will be lost. (no pumping occurring, i mean).

i think that a bigger radiator or one with more rows of cooling tubes is the silution, that and perhaps rigging the aux electric cooling fans to run more often.

You are right on that, a bigger/faster pump would not be the solution, removing heat from the coolant is the solution, or improving the thermal cooling transfer ability of the coolant - there are additives like water wetter and using less antifreeze in the mixture will help improve cooling but only so far! A bigger or better radiator is the answer, aside from assuring that the thermo clutch is engaging at the proper temp (proper for cooling, not for emissions!).

The Grapevine is the acid test for any cooling system, whenever I've driven that stretch I've always seen a car alongside the road with the hood raised and steam coming out of it. The problem is getting across the truck lane, that is something I would hate to have to do with those big rigs literally crawling along

OK, (third post on this thread, I am hung up on cooling on the 603 engine!)
I am interested. I need a radiator for another '87 I am working on and I would consider buying a 3-row in a heartbeat, if it was the same size as the original. please ask your mechanic, I have a three row on one of my 123's and can tell you it makes a big difference! I won't need one for a month or so (the head is being sent to be rebuilt) but was planning on looking for a custom welded alternative if a rebuilder can't be found that does 3-row upgrades. This car is going to Texas and I want it to run cool!

i will
 

check and post results.

tom w

I have my aux fan running on high 100% of the time, it seems to not be a problem at idle even with the a/c on but when under load is a diff story. I think I will try the set up mentioned earlier on this tread using the clutch from a Mazda or mitsubishi truck, if it works its a lot better than sinking $200+ on a OEM fan clutch as opposed to maybe $10 to $20 at the pull it yourself yard. If you get 2 years out of it then you just go get another one :D