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#1
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Running Hotter on HWY than City
83 300CD
Ambient temperatures in high 90s to low 100s last week or so. I've made two two-hundred mile round trips in the middle of the afternoon with the AC running, cruising between 70 and 80 mph. After replacing the thermostat (new one boiled and checked out prior to installation) and the temperature sender on the engine block, and of course filling and burping the cooling system appropriately (Zyrex g05 of course), I'm getting the following readings: Between 70 and 75 mph, 100C 75-80 105C 80+ rising up to around 110C The fan clutch seems to be working as there is no play, plus I don't think that's the problem because in town, in city driving even with the air conditioner on, the temp settles around 90 and never above 95C. It's just curious to me that its running hotter and hwy speeds than stop and go in town with the same ambient temperature readings. Seems like it's something other than t-stat or even radiator. Would the water pump be involved in a problem of this sort? Or perhaps a blockage somewhere?
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1983 300CDT -- 177K |
#2
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What temp is the stat? What temp did it open at when you did the boil test? Did you put the stat in facing the correct direction?
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85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#3
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Stats a 90C at full open. Spring to block, so yes. Approximately 70/30 antifreeze to distilled water ratio.
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1983 300CDT -- 177K |
#4
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radiator
You have found it's limits of heat transfer. Either air is blocked from flowing through it (clogged fins with leafs, debris, bugs) or coolant is blocked from flowing through it (clogged tubes, in the old days - recore, now - replace)
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Greg 2012 S350 BlueTEC 4Matic 2007 ML 320 CDI 2007 Leisure Travel Serenity 2006 Sprinter 432k 2005 E320 CDI 1998 SLK230 (teal) 1998 SLK230 (silver) 1996 E300D 99k, 30k on WVO Previous: 1983 240D, on WVO 1982 300D, on WVO 1983 300CD, on WVO 1986 300SDL 237k, 25k on WVO (Deerslayer) 1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix 1983 380 SEC w/603 diesel, 8k on WVO 1996 E300D 351k, 177k on WVO |
#5
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Greg,
I was thinking radiator. I examined the fins and they seem to be fine. Would just removing the radiator and taking it to a shop for a dip in the tank be sufficient, or should I spring for a new radiator? Also, how bad are these temperatures? Ive read on this forum that 100-110 is fine for the 617 because it's an iron block, but I've also read that thats too hot. Any thoughts on this?
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1983 300CDT -- 177K |
#6
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You are not doing yourself any favors there. More isn't better when it comes to heat transfer.
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#7
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yeah, change it to 50/50 for best compromise in cooling/ corrosion protection.
Have you checked the water pump belt tightness?
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85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#8
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How's your transmission fluid level?
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1977 300d 70k--sold 08 1985 300TD 185k+ 1984 307d 126k--sold 8/03 1985 409d 65k--sold 06 1984 300SD 315k--daughter's car 1979 300SD 122k--sold 2/11 1999 Fuso FG Expedition Camper 1993 GMC Sierra 6.5 TD 4x4 1982 Bluebird Wanderlodge CAT 3208--Sold 2/13 |
#9
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X2 on this. Remove it and have it checked by a REPUTABLE radiator shop. Make sure the tanks are not rotted. I was able to have mine retanked a few years ago. The core was fine. A partially plugged radiator will do exactly as you describe at hwy speeds. The engine is producing more heat than the radiator can exchange to the air going across the fins and flues. OR, just replace it
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Thanks, Mark in NC "Spark plugs?...We don't need no stinking spark plugs!" 1985 300SD "Der Silberne Schlitten" 420,000 mi Wish these were diesel: 2003 Ford Club Wagon 130,000 mi |
#10
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x2 + Fan Clutch
The radiator has to be good to go as others are posting but I'll bet on a not so healthy fan clutch.
A sick verses dead fan clutch will seem like it is working however at sustained higher rpms i.e. highway driving it may only be spinning at a fraction of what it needs to be to yank enough air through the radiator to keep coolant cooler while the engine is generating higher temps. In other words it may not be engaging up as needed. Instead slipping and pulling less air resulting in lower heat exchange rates. Around town rpms will be all over the place and the fan clutch may be handling the lower rpms and pulling adequate air thus keeping temps down.
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1986 300SDL 440,xxx |
#11
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You don't need any fan at freeway speeds. If the problem was around town, then I would look for lack of air flow. No problem around town means the t-stat is working and the fan is working.
A new radiator is $233 at Fastlane. Click on the "Buy Parts" link at the top of the page.
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Greg 2012 S350 BlueTEC 4Matic 2007 ML 320 CDI 2007 Leisure Travel Serenity 2006 Sprinter 432k 2005 E320 CDI 1998 SLK230 (teal) 1998 SLK230 (silver) 1996 E300D 99k, 30k on WVO Previous: 1983 240D, on WVO 1982 300D, on WVO 1983 300CD, on WVO 1986 300SDL 237k, 25k on WVO (Deerslayer) 1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix 1983 380 SEC w/603 diesel, 8k on WVO 1996 E300D 351k, 177k on WVO |
#12
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The temps on the gauge you are seeing with 100F ambient with AC on and doing 80 mph may be consistent with the 90C stat you have. Try a 80C stat, that should bring the temps down.
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85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#13
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Quote:
What was the cost of this procedure? Does anyone think it's more worth it to try this route or just spring for a new radiator?
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1983 300CDT -- 177K |
#14
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Quote:
The symptoms of a bad fan clutch are precisely the opposite of the ones described here. Considering that a new Nissens radiator can be had for under $200, it doesn't make sense to attempt to salvage a (presumably) 30 year-old radiator. But it also doesn't make sense to replace a possibly good radiator without additional investigation. Last edited by qwerty; 07-02-2012 at 10:56 AM. |
#15
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My best guess is a partially clogged radiator... you CAN have it re-tanked and flushed for ~$60... but since the radiator is a pretty important part of the engine, I'd just spring for a new one
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1978 w123 300D astral silver "Benzie" 1980 w123 300CD orient red "Benzie 2" 1994 w124 E500 "Big Black" 1998 w163 ML320 "Ole' Faithfull" 1969 Datsun 2000 roadster |
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