When I've been driving for a while the needle is between 80 and the next line (100?). Sometimes it gets close to the "100" mark (usually when I'm sitting at a light) but never passes it. If I turn on the heat full blast it goes down close to 80.

So I guess my question is.... Is hitting 100 too hot or is that within normal heat?

digi

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1984 300td euro turbo

Too hot would be something more like 120C. The red part of the temp gauge.

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)

So what I'm experiencing is somewhat normal temps?

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1984 300td euro turbo

80C and just a couple of degrees higher, seems to be the average temperature of most 603 cars discussed on this forum. Consensus is, that heat is the enemy of the cylinder head. Closer to 80C is better.

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1987 300D 146K Original #14 Head
One eye on the road, the other on the temp. gauge

Gone But Not Forgotten
1983 380 SEL Long gone
1983 300SD Wish I hadn't traded it in on a 90' Corvette
1989 300SE My all time favorite
1995 E420 Went like a bullet

Perfectly normal.

The fan will start somewhere a little over 100C. Therefor, at a stand still, you basically have no cooling until the temp goes a little over 100C. If it continue well past 100C you shuld have things checked.

I had to replace the radiator on mine, as it was clogged.

I dont think this is quite right. You have plenty of cooling at a standstill...all that water running through a healthy cooling system is plenty to keep the car cool at idle.

Unless you have your foot on the brake and revving it to 3k for minutes at a time in drive...then there's no helping you :-)


On a W123, if your cooling system is 100% healthy you should experience little to no fluctuation in coolant temperature unless you are in a constant high load situation - like going up at a steep hill at 65mph for minutes at a time. Or AC is running on a really hot (90 degree +) day sitting in traffic.

Id suggest buying an IR thermometer at Harbor Freight to verify the head temperature. I have replaced the temp senders on both of my 123's because they drift up over time and read higher temps than they should.

If all things are working right - including the temp sender, and there is a correct 80C thermostat installed - the temp should be around 83-87C on the dash.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

That is almost right, but the water does not cool anything as long as it is not cooled by air passing thru the radiator. When the car is stationary, very little air passes thru the radiator. The fan never stop completely, so there is some circulation, but on a hot day with AC working hard, the temperature may raise up to approx 100C. This is more common on the petrol models, as they produce more heat when idling. Techincal documentation on the 300 TD Turbo say the viscose engage fully at 102C engine temperature (air temperature thru the radiator is 72C). The electrical fan engage at 80% when the pressure in the AC system goes over 18 BAR (it stops when pressure goes under 15 BAR). The electrical fan will also engage 100% if the engine temperature goes over 105C.
Revs will not go over 1500 rpm with the foot on the brake :-)

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-1992 300 TD Turbo
-198 2600E
-2004 E240 4matic LPG
-2000 Jeep
Editor, Norwegian Mercedes-Benz Enthusiasts Club Magazine MB Tidende www.mbentusiastklubb.com

The temperature in my 300SD behaved almost exactly the way that you're describing until I did a citrus flush. Now it's always between 70-80C even under severe conditions (stop and go traffic + warm weather). I bet you've got the same problem I had.

I attributed my problems to *internal* obstructions in the radiator reducing the coolant flow, mostly scaly white deposits from hard water and corrosion... has your 617 ever had green coolant inflicted upon it? I could see deposits anywhere I looked in the cooling system, including on the insides of hoses and in the thermostat housing. They were gone after I did the flush.


The citrus flush is a bit time consuming, but not difficult (unless you snap a bolt in the thermostat housing while opening it up like I did ). First you remove the thermostat and coolant, then refill the system with a quart of shout and water and drive around the block with the defroster blasting. They you flush the system with water a few times until it stops coming out soapy. When doing this it is essential to open the drain plug on the engine block to completely drain the fluid on each rinse or you'll never get all the soap out. Then fill it with a citric acid solution, drive hard for an hour or so, and rinse it out a few times.

The difference was astonishing. After the soap, every rinse was coming out a rusty brown color, but by the last rinse after the acid, the water was coming out as clear as it went in. My engine would frequently touch 100 before, and never drop below 85. Now it consistently runs between 70-85C.

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-Brian

1984 300SD, 375XXX miles, Light Ivory w/ Palomino TEX

What can I do to get my car temp lowered by 10C?

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1984 300td euro turbo

You've got an iron head 617. Not nearly as finicky with temps as the Al headed 603 motors.

Anywhere between 80 and 100 is OK. Most usually run in the 85C range at all times.

If you want more constant temps:

Step #1: Replace radiator cap
Step #2: Check fan clutch
Step #3: Check/change thermostat and flush coolant

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Thanks!

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1984 300td euro turbo

What's the status of your viscous fan clutch?

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92 300D 2.5L OM602 OBK #59

I'm not sure! I will have to check it!

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1984 300td euro turbo

On my 81 SD I installed the smaller water pump pulley with the plastic fan .
My temps went from 100* down to a steady 80*

On your 84' I think that's already done though.

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Experience : what you receive 3 seconds after you really needed it !!



86 300SDL 387,000? Motor committed suicide
81 300SD 214,000 "new" 132,000 motor
83 300SD 212,000 parts car
83 300SD 147,000

91 F700 5.9 cummins 5spd eaton 298,000
66 AMC rambler American 2dr auto 108,000
95 Chevy 3/4 ton auto 160,000
03 Toyota 4runner 180,000 wifes

I thought the small pulley was standard on all 83 and up vehicles, but apparently it's only for the SD chassis. his TD would be a 123, so it should have the large pulley, perhaps he can check the size belt he uses, and see. if it's 1035, it's the large pulley, 1000 is the small one.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!