Kinda dumb, but is the electric fan spinning the right way?

__________________
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

Lol...I wondered that too. Electric fan and clutch fan are both spinning the proper direction.

Check with Steve/swogee. He might have figured out his similar hot running issue with his 87 TD.

1987 300TDT Overheats on long hills

Sixto
87 300D

try testing the fan clutch, even when bad, the cooling fan will spin proper direction, but not pull air effectivly through radiator, try the rolled up newpaper test to verify if the cluch is 'locked' when at a hot temperature.
seems you overlooked this problematic issue.

I did not see where the water pump was changed. Impeller corrosion can seriously reduce flow.

A digital temperature gun us available at Harbor Freight for about $25.

Thanks Sixto for the link to that thread, gave me some good ideas and I will definitely send a PM to Steve to see if he ever tracked down the issue.

I do have a new question though: would one normally expect a temperature difference between the upper radiator hose itself and the metal housing that the temp. sending unit screws into? Unless I'm just a tard with my IR thermometer, there seems to be about a 9C difference, with the housing part being cooler. In other words, the upper radiator hose temp as taken with the IR thermometer matches the gauge reading, but the temp on the housing itself is about 9 degrees cooler than either the upper radiator hose or the temp gauge reading.

Is that normal? If so, which is the proper reading: housing or hose? If it's the housing, I think it's possible I simply have a faulty temp gauge.

Something else that points to this is that I couldn't get my AUX fan to kick on high, even at an indicated 110C. I realize I said before that it worked properly, but I think I was confusing it for the AC function. The sending unit for the high speed function is brand new OEM from the dealer, so unless it's faulty it may simply be that the engine just isn't as hot as the gauge says it is. Unfortunately I didn't think to get an IR temp reading when the indicated temp was 110C today so I'm not sure about this theory quite yet, but I'll test it tomorrow.

I also diluted the coolant mixture down to roughly 65/35 and added a bottle of Water Wetter. I can still get it up to 110C, but it is significantly harder. As in, I have to really try. Normal driving it wouldn't go over 105.

I did mention that the fan "roars" when it is on and is quiet when once the car cools down, but you're right I didn't do any actual testing on this. I realize the newspaper thing is an old trick, but I'm a bit skittish about sticking anything into the fan blades while it's spinning. Call me paranoid I guess.

I read that another way to test the fan is to stop the engine with the stop lever under the hood while the fan is (or should be) engaged and observe how long it takes for the fan to stop rotating. When disengaged it will "freewheel" for a while, when engaged it will stop almost immediately. My fan stops almost immediately - within maybe 2 revolutions - when I hear it roaring (i.e. engaged) and freewheels when I do the same thing at a lower temp, so I'm fairly confident the viscous clutch is functioning properly.

I have a digital temp gun - what sort of temperature difference would one expect between the top and bottom radiator hoses if the water pump is functioning properly?

Also, when the thermostat is open coolant pours freely out of the top of the radiator with the top hose disconnected. Not like a fire hose or anything, but definitely a good amount. Any other way to test this?

The water pump impeller can become pitted over time and use through erosion, especially the cast ones. When this gets bad enough you get cavitation and low coolant flow. Once a bubble forms the pump isn't pushing all the coolant it normally would when new. My pump didn't leak and turned smoothly, but I was running hotter each year. Replaced radiator when the neck cracked - no change. Replaced thermostat and cap - no change. Replaced pump - back down to like new with no other change.

__________________
1992 300D 305+K miles
1978 240D Sold

You're getting burned by emissivity, which strongly affects IR radiation (in and out). See http://en.wikipedia.org/wiki/Emissivity. The shinier"metally" the surface, the more useless the data.

Roll up the newspaper and jam (not really, more like slowly feed) it in there; the side of the fan we are exposed to will "shed" or "reject" an item jammed into it rather than snag/bite/chew it.

__________________
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 would pull the water pump before you buy a replacement, no sense buying one if thats not the problem.

__________________
-Randy Wakefield

1969 220D 4 speed (parts car)
1976 280C
1976 280S
1981 240D 4 speed (parts car)
1982 300D
1983 300TD (Ivory)
1983 300TD (gold)
1985 300TD (gray)
1987 190D 2.5
1970 280SEL (sold)
1977 240D 4 speed (sold)
1974 280 (rusted to death)
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1927 Chevy 4 door sedan
1938 Chevy 2 door sedan
1950 Willys Jeepster
1955 Studebaker President 4 door
1977 Ford F250
1979 Glastron 17'
1948 John Deere A
1960 John Deere 2010
1979 Satoh S650G
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2000 Bichon (Doby)

Generally speaking I'd agree with you, however since this car is my only transportation I'd rather just have a replacement on hand if I need it rather than have to pull it apart twice or leave it pulled apart for a day or three while sourcing a new pump. Mostly it's a time thing. I'll just return the new one if not needed.

I did the newspaper test yesterday: the fan shredded the paper when engaged, paper stopped the fan when it was not engaged.

One of the symptoms I'm having is that the car gets hotter after I let off the accelerator on a hard run - like 1/4 mile for example. I read that this behavior is indicative of a corroded impeller. Being that's the only thing I haven't replaced and there's no sign of a blown head gasket, I'm hoping the pump is the culprit. Will keep you all posted, thanks for the suggestions so far .

So I replaced the water pump and upper radiator hose, same issues.

Also drilled a few holes in the exhaust to rule out a clog and excessive backpressure issues. Same problem.

Running out of ideas aside from head gasket/cracked head - which my poor little brain doesn't even want to contemplate right now.

Time for a compression test I suppose.

I am having some similar issues - so please post if you come up with a solution.

Thanks.

Just for the hell of it and the time required. Set the balancer to the approved degrees setting for your 603 model. Take a small mirror and check for the indicator tang in the injection pump being present and more or less centered.

Your fuel milage to me sounds low perhaps for a 603. It would not take too much decreased efficiency to cause the problem. Next time out also come to a stop without using the brakes after a few miles and verify the wheels are all the same temperature. Some dragging brakes could be present.

Is the indicator on the bottom of the IP? Sorry, I'm not familiar with its location.

Good idea regarding the wheels I'm headed to Wally World in a few minutes, will find a spot to do that. Just use the IR thermometer like in the middle of the outboard side of the wheel? Or do I need to crawl under or something?

Thanks .

Ok I did what you suggested regarding stopping without brakes (that was interesting...). Checked the wheels and the rotors themselves.

The front wheels were approx. 32C in the middle of the outboard side of the wheel, approx. 34C on the rotor. The rear wheels were approx. 34C on the wheels, approx. 38C on the rotors.

I hadn't used the brakes for about 1.5 miles when I found a place to bring it to a stop, so unless one would expect the rear wheels to be hotter for some reason I can't think of, it would appear that the back brakes are hanging slightly. Not sure if it's enough to cause my problem, but then again it can't be helping anything.

I looked around and I have a general idea of where to look for the indicator tang on the IP, but I welcome any specific direction you care to provide.

Thanks