Quote:
Originally Posted by draaronr
81 300sd, just replaced the water pump as it was failing all else seems normal. temps were seemed to be climbing and I could hear the pump beginning to fail, but after change of pump it still seems kind of high, this is driving for 10 minutes and getting up to 75mph for 5 minutes. outside temperature is 90 and ac was on, thoughts ideas?
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I will assume you have heeded the advice of others here and checked to be sure you have removed all the air from the system.
Have you tried running without the thermostat for test purposes only???
Let me give you an example of what a stock, correctly functioning cooling system on a 300SD should be capable of.
My 1978 300SD has the stock radiator, which has been cleaned once since I have owned the car. I am using the 11 blade plastic fan (later model) with the stock thermostatic clutch. I use 40% coolant to 60% distilled water here in Central California.
My engine produces 14.5 lbs boost at WOT in second gear and the ALDA is backed all the way out, CCW. The engine is internally stock with the exception of Gapless Piston Rings (custom by Total Seal) and the later '05' camshaft.
I am running both the factory gauge in the instrument cluster and a Stewart-Warner machanical temperature guage, both tapped into the cylinder head.
For testing, I take an old thermostat and remove the valve, so the only thing I am installing is the thermostat body.
If you refer to the attached image, you will notice I am running 144°F @ 75 mph (about 3200 rpm) at 95°F ambient with the A/C on. The 144°F reading is based on the mechanical gauge, which is close to what the factory gauge is reading.
The second photo will show you my stock radiator. There is no trick core here, or aluminum replacement, just a 1978 radiator that has been cleaned and resoldered.
Climbing the Grapevine south of Bakersfield in 95°F to 100°F temperatures, the coolant temp will come up to about 177°F to 180°F and stay there, again verified by the mechanical gauge.
This should demonstrate what the cooling capability of a properly functioning, stock system can do.
With an 80°F Whaler Thermostat, my temperatures run about 180°F at cruise and won't go over 190°F under load, or during periods of extended idle. My auxilliary fan will only come on at 100°C, and I have had to block the radiator with a blanket to push the heat up far enough to test the circuit. The car will not get over 190°F on its own, under any conditions.
My wife just returned from a trip to Hesperia in the High Desert and all her passenger's remarked on how cool the engine ran and how cold the A/C was.
At night, you can watch the thermostat cycle. The temps will drop down under 175°F, and then come back up to a little over 180°F, then drop back down again. You can set your watch by the movement of the factory and aftermarket (mechanical) guages as they rise and fall in unison.
Aside from air, I have seen a restriction in the radiator cause the lower hose to try and collapse at higher rpm and I have also seen thermostats that will only open partially at their rated temperature.
I would suggest testing the system without a thermostat and verifying your in-dash gauge with an underhood or in-car mechanical guage.
I hope this helps....Robert
__________________
Did you just pass my 740 at 200 kmh in a 300SD?????
1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013
100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
