Hi,

I recently purchased an 87 300sdl. The car gets up to running temp in about 10 blocks. It has been running over 100 degrees on the highway even without the AC on. At idle, I can get the temp to come down by reving the engine.


New MBZ thermostat
New Fan Clutch
Behr Radiator Looks fairly new
#17 Head
Aux fan comes on OK

My mechanic thinks it's the water pump or head but he's not sure. I'm thinking the water pump since the head was replaced already(don't know when) and the car gets up to temp so quick. Also the reving at idle will bring the temp down quick.

Any other thoughts?

Thanks

What about air in the system or a t-stat installed backwards?

Can you remove the t-stat, take it for a test run, and see if it still over heats?

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

How long ago was the #17 head installed?

Sixto
87 300D

I had the same problem before I installed the new thermostat.
I'm not sure when the new head went in. Car is very well taken care of.

Running temp within 10 blocks... how hot or cold is the radiator core at that point? How hot or cold is the lower hose? How stiff is the upper hose? I wish I had an IR thermometer to give you reference numbers. Hint to someone who has such a device

Sixto
87 300D

Have you done a test to see if upper radiator hose is pressurized from a cold start? When you wake up tomorrow morning, pop the hood. Make sure there is no pressure in cooling system, then crank the car up and see if the radiator hose pressurized within 5 minutes or so...let us know how long before it gets hard. No homo.

__________________
1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

Ok. I'll test to see if my car has "morning wood"

"10 blocks" is a bit relative. In some areas you could to that in 90 seconds, in others 10 minutes. What's the real deal, along with "morning wood" test results?

__________________
James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
1996 Suburban K2500 (192k, 6.5 turbo diesel/4WD towmaster 10,000)
www.engineeringworks.biz
1987 300SDL junker 170k
1982 300SD junker, 265k

OK. The morning stiffness test results:

Easy to pinch, little to no pressure. Also, there's little pressure after the car sits for an hour.

Radiator cap inspection looks good, seals look ok, 140 stamp.

I'm up to temp in 1/2 mile or less.

You forgot this part. Just idle for a bit with a cold engine. Hose should stay "soft" (unpressurized) until engine warms up and vapor pressure of heated water/gylcol come to a new equilibrium. It should NOT blow up "right away" due to compression/combustion leakage.

__________________
James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
1996 Suburban K2500 (192k, 6.5 turbo diesel/4WD towmaster 10,000)
www.engineeringworks.biz
1987 300SDL junker 170k
1982 300SD junker, 265k

I let her idle for 5 minutes this morning and there was no notable increase in pressure in that hose.

Sounds like it's time to consider a clogged oxidation catalyst.

Sixto
87 300D

The engine has no visible blowby.

Hydraulic valves wont as much. If the tstat has not been replaced thats a good place to start.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Tstat has been done. Are there signs that it could be the water pump?