300E running hot...new rad?? - PeachParts Mercedes-Benz Forum

Zeus · #1 09-24-2002, 04:28 PM

My trusty 300E is running a little hotter than usual lately. It has always stayed at 80-85C but lately was been wandering up to 100C at idle. On a few hot days, the aux fan has kicked on when the temp climbed even higher.

I've read through as much info here as I could and I've performed the following:

- new BEHR thermostat (87C)
- flushed the old coolant and added new coolant
- removed radiator and sprayed clean with a hose and then blew out any remaining debris with compressed air (I did this last bit from a distance so that the pressure would not damage the thin walls of the rad)
- checked all hoses, connections, etc.

The car is still running hotter than usual. It never used to climb to 100C. I thought cleaning the rad would do it as it was encrusted with bugs, dust and dirt but to no avail.

Before I buy a new radiator are there any other suggestions?

dtanesq · #2 09-24-2002, 06:55 PM

Yes.

Try a thermostat with a lower temperature rating. I think the one the tech installed in the 300E noted below was a 72 degree thermostat. In this part of Northern California it's very hot in the summer and the 300E (and now the TE), tended to act like it was going to overheat when idling for any period of time. The 300E no longer does that. It now belongs to a friend and he reports no problems. The TE does act squirrely sometimes - has the 87-degree thermostat, but not for long.

By contrast to the wandering temp gauges on the W124s, my straight-six E34's temperature gauge, once at operating temp, never moves. (Perhaps I'm being deceived by a faulty gauge or sender unit. The fuel gauges on E34s can be inaccurate. Mine certainly is.)

anthonyb · #3 09-24-2002, 07:09 PM

How's the fan clutch?

Mike Richards · #4 09-24-2002, 07:54 PM

A fellow I work with told me this morning that his 300E started running hot as was described in the first post here. He replaced the expansion tank pressure cap(radiator cap to some). They do get weak and can cause pressure loss. When the pressure goes down, the temps go up. This fixed his problem.

Something to consider and much cheaper than a radiator which may not be bad.

Piotr · #5 09-24-2002, 10:27 PM

check your fan switch and fuse, but the symptoms are more in line with the expansion tank cap

#6 09-25-2002, 06:37 AM

With the engine stopped, spin your fan hard by hand. If it turns more than about 1/2 turn, the clutch is bad. This will cause a dramatic increase in temp in stop and go traffic.

Good luck,

rdanz · #7 09-25-2002, 09:53 AM

I had the same problem you describe changed expansion tank cap and the problem was solved thanks to the info I got here.
Good Luck

-fad · #8 09-25-2002, 10:42 AM

fwiw- my '94 E500 was running just a tad warmer than usual @ 90 degrees over the weekend (70-90 degree ambient temps) and had a little coolant seeping from the top of the plastic coolant overflow bottle...

>replaced the cap and she's back to cool cool cool- back at 85 degrees constant in 75 degree ambient temps! Happy Happy!

-fad

Zeus · #9 09-25-2002, 11:38 AM

wow...a bunch of excellent suggestions! Thanks to all. I'll head home tonight and try them all. The rad cap looks ok, but I've never replaced it so it might be time. Not sure about the fan clutch - the fan seems to run ok, but I'll try turning it by hand as Larry suggested... I'll let you know how it goes...

Zeus · #10 09-26-2002, 09:40 AM

Larry - After driving to work this morning, I turned off the engine and opened the hood. With the engine still warm, I gave the fan a crank as you suggested. It spun merrily - several rotations at least. It also spun in both directions. Do I need a new clutch and if so is this a DIYer? Thanks...

#11 09-26-2002, 10:01 AM

You definitely need a new clutch. It's not real difficult, but there are two special tools for the job. With ingenuity you can work around your lack of those tools.

The first tool is nothing more than a bent piece of rod that's about 1/4" or so in diameter. It goes in a notch in the front of the timing cover and locks against a notch in the fan pulley or some other rotating part connected to the fan clutch. This keeps it from turning while you are loosening the allen head screws holding the fan to the clutch or the clutch to the hub, I don't remember which. Those allen head bolts have very little clearance between them and the radiator. This is where the other special tool comes in, which is a very short allen head to 3/8" drive extension.

What you might be able to do is lock the fan with the rod tool and then unbolt the clutch from the hub, get the shroud out of the way and get the fan/clutch subassembly out on the bench.

With a little ingenuity and determination, you should be able to accomplish the repair.

Good luck,

Zeus · #12 09-26-2002, 10:21 AM

Thanks for the input and the work tips Larry, much appreciated. I'll grab myself a new fan clutch and install it this weekend hopefully. I'll send an update when it's done. Thanks again to all for the advice, I've said it before - but no harm in doing so again - this forum rocks!

Chris

Mike Richards · #13 09-26-2002, 10:33 AM

It also helps to have a LONG 3/8" dr. breaker bar to access the bolt that secures the clutch. There's very little room between the clutch and the radiator. With a longer breaker bar, your hand is higher up with some room to work with.

Stahlwille makes the special 8mm allen socket that fits this bolt. I'm not saying you must use this tool, but will say that the metal in the head of this bolt is VERY soft and rounds off VERY easily.

http://www.************************ sells the rod and the 8mm allen socket. The locking rod Larry described can indeed be homemade. All you need is something to prevent the hub from turning while you loosen the 8mm allen bolt that secures the clutch.

csnow · #14 09-26-2002, 04:17 PM

Once you stop the clutch from spinning, you can just use an ordinary 8mm L-type hex key wrench to remove the center bolt.
Put a 1 ft (or so) length of 3/8 steel pipe on it for extra leverage.
No special tool required this way.
Tough to get a hex-key socket in there, and that radiator is fragile (and expen$ive).

I also cut my fan shroud at 9:00 and 3:00 so that it can be removed with the fan on. Re-attached the 2 sections with zip-ties.
Not pretty, but saves a lot of trouble anytime you want to access the front of the engine...

Best of luck, and happy wrenching.

Zeus · #15 09-27-2002, 02:25 PM

Well the mystery deepens...

I installed a new radiator cap yesterday and that didn't fix the problem (I didn't think it would but for $8 I thought I'd eliminate it from the equation). While I was at my mechanic's he looked at the fan clutch and didn't think anything was wrong with it.

He agreed that the problem is related to restricted airflow and suggested I clean out the air conditioner condenser/radiator in front of the radiator as well as it was very dirty and could be inhibiting airflow into the rad. At the moment it is encrusted with dead bugs, small stones and dirt.

I think I will try this before I tackle the clutch...I wish I had done it when I removed the rad for cleaning last time, oh well, hindsight is 20/20...

If this doesn't fix it, I'll replace the clutch (my mech has a used one for me)...