engine overheats, upper radiator hose cold, thermostat works
#3051862
06/19/22 10:55 PM
06/19/22 10:55 PM
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Joined: Jul 2003
Posts: 3,374 Rancho Cordova, CA
Exit1965
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Trying to track down a recent (didn't change anything) overheating problem on my 73 d200 with a 360.
When I start the engine from cold, it gets up to about 230 after roughly 6 minutes of idling or low rpm in park before I turned it off. The upper radiator hose never warmed up in that period of time. I took the thermostat out to test (and it was in plenty of water in the thermostat housing), and it's opening at 180 when I test it in a pan of water. The radiator is full, and I don't see any leaks. The thermostat, upper and lower radiator hoses are all fairly new (1-2 years), and it had always been running at normal (180ish) temperatures before the past couple of times I've driven it.
Does that indicate the water pump itself is bad? It seems like it's not pumping otherwise I think the upper hose would get hot at 180+ degrees (certainly by 220+), yet when I think of a "bad water pump" I usually think of leaking which I don't think it is.
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: Exit1965]
#3051865
06/19/22 11:18 PM
06/19/22 11:18 PM
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Joined: Jan 2003
Posts: 20,645 So Near, Yet So Far
topside
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Test: leave the t-stat out, fire up, see if water in radiator is flowing or static. I'll assume static check of fan wobbling shows none, and no noise from water pump indicating breakage. Fan clutch ? Direct drive fan ? If no circulation, there's either a blockage or the pump isn't working. Blockage could be anywhere in the system (upper or lower hose, pump, housing, block, heads. Do you get any heat out of the heater ? (Not that it could cause that problem, but it'll be a secondary symptom.)
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: Exit1965]
#3051968
06/20/22 12:14 PM
06/20/22 12:14 PM
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Joined: May 2019
Posts: 6,175 nowhere
Sniper
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Not collapsing the bottom hose as far as I can see.
The 230 is from the digital water temp gauge. In 90 degree f weather, it seems it would be unusual to run an engine for 5-7 minutes without reaching 180. At which point hot liquid should begin to flow into the upper radiator hose as long as the thermostat is working, which it is. I think that's why I'm not believing it's just a bad temperature reading.
Gauge senders go bad. I would verify the readings with an IR gun or similar. Harbor Freight has them for cheap. Did you run it up to temp with the cap off an observe any water flow thru the radiator? Can you try this without a thermometer installed, to eliminate it?
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: Exit1965]
#3051996
06/20/22 01:51 PM
06/20/22 01:51 PM
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Joined: Jan 2003
Posts: 15,197 Omaha Ne
TJP
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It's a direct drive fan. I didn't try a wobble check but will try that. There is some kinda rotational noise now that you mention it, though it's subtle and I haven't tried to pinpoint it. There is no heater on the truck anymore, so that outlet on the water pump is capped.
Thanks for the ideas. I'll see what it does without the thermostat in it tomorrow. Would I expect to see lots of activity in there if the pump was working OK? You should see the same activity with the stat open and the engine at 2K or more RPM. If not I would suspect a slipping belt, Impeller not turning, (off the shaft, loose on the shaft or broken shaft) or a blockage. keep in mind the blockage can be a plugged radiator, collapsing lower hose, T'stat not opening or installed upside down. Something is keeping the water from flowing, the question is WHAT ? Keep us posted
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: Sunroofcuda]
#3052122
06/21/22 06:24 AM
06/21/22 06:24 AM
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Joined: Jan 2021
Posts: 948 rust belt
Moparite
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I took the thermostat out to test (and it was in plenty of water in the thermostat housing) Does the t stat have a bleeder valve? If not it will trap air and cause the problem you experienced. This goes for all LA and magnum motors. If the t stat doesn't have the bleeder valve drill a small hole(3/16-1/8) in the flat part of the t stat. This will let the air out when you fill it. If it does have the bleeder valve i would say the water pump is not moving the water.
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: Moparite]
#3052214
06/21/22 03:41 PM
06/21/22 03:41 PM
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Joined: Jan 2010
Posts: 1,440 NW Chicago suburban area
Mopar Mitch
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NW Chicago suburban area
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I agree with the T-stat.. must have a bleeder hole of decent size (~1/8-3/16").. I recently experienced the same problem... had an air pocket blocking flow after I replaced a lower hose... they apparently don't make many new T-stats with the bleeder hole... they should!
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: Mopar Mitch]
#3052222
06/21/22 04:47 PM
06/21/22 04:47 PM
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Joined: May 2019
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A bleeder hole isn't really required for our old stuff. But if air pockets concern you the best way to fill the cooling system is the vacuum method. No air in the system at all if you do that, which is also the way the factory did it and the reason older cars had a spring in the lower hose. I got a fairly cheap kit on Amazon, pumped my cooling system down to 23.5" and filled it with new coolant. Done. No air pockets, no burping the system. https://board.moparts.org/ubbthread...1951-plymouth-cambridge.html#Post3043150
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: Cab_Burge]
#3052246
06/21/22 08:19 PM
06/21/22 08:19 PM
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Joined: Mar 2011
Posts: 3,056 Michigan
A727Tflite
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Three days from the most logical approach mentioned by Topside - check for coolant flow.
Still waiting, and waiting, and....
Last edited by Transman; 06/21/22 08:20 PM.
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: A727Tflite]
#3052272
06/21/22 09:45 PM
06/21/22 09:45 PM
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Joined: Jan 2003
Posts: 15,197 Omaha Ne
TJP
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I Live Here
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Three days from the most logical approach mentioned by Topside - check for coolant flow.
Still waiting, and waiting, and.... I'll politely disagree with it being the most logical approach as doing so may mask a partially blocked radiator that may show more flow without the T/ Stat restriction. In my experience over the last 50 or so years, if increasing the RPM to 2-3K shows no flow one needs to investigate why. other causes are mentioned above. I will agree with you on the waiting part
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: TJP]
#3052279
06/21/22 10:08 PM
06/21/22 10:08 PM
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Joined: Mar 2011
Posts: 3,056 Michigan
A727Tflite
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Three days from the most logical approach mentioned by Topside - check for coolant flow.
Still waiting, and waiting, and.... I'll politely disagree with it being the most logical approach as doing so may mask a partially blocked radiator that may show more flow without the T/ Stat restriction. In my experience over the last 50 or so years, if increasing the RPM to 2-3K shows no flow one needs to investigate why. other causes are mentioned above. I will agree with you on the waiting part His first post - “ didn’t change anything” - now it over heats. Why would one assume anything is blocked. Logically - pull the stat and see if you have flow. If nothing, first order of business is check the pump.
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Re: engine overheats, upper radiator hose cold, thermostat works
[Re: A727Tflite]
#3052287
06/21/22 10:42 PM
06/21/22 10:42 PM
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Joined: Jan 2003
Posts: 15,197 Omaha Ne
TJP
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I Live Here
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Omaha Ne
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Three days from the most logical approach mentioned by Topside - check for coolant flow. Still waiting, and waiting, and.... I'll politely disagree with it being the most logical approach as doing so may mask a partially blocked radiator that may show more flow without the T/ Stat restriction. In my experience over the last 50 or so years, if increasing the RPM to 2-3K shows no flow one needs to investigate why. other causes are mentioned above. I will agree with you on the waiting part His first post - “ didn’t change anything” - now it over heats. Why would one assume anything is blocked. Logically - pull the stat and see if you have flow. If nothing, first order of business is check the pump. In the same post he said I took the thermostat out to test (and it was in plenty of water in the thermostat housing), and it's opening at 180 when I test it in a pan of water. Which is why i suggested increasing the RPM, However with a cold upper hose and a stat that tested OK, if the belts not slipping Likely the pump hub, shaft, or impeller. We're wasting out time trying to help someone who's not responding so
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