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03-02-2024, 10:38 PM
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#1 |
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Registered User
Join Date: Apr 2002
Location: Manitoba, Canada
Posts: 663
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L6 - 250 Overheating
Stuck with the 250 till the 383 is done.
Have lots of trouble with overheating. Put in a bigger rad, tightened all the clamps, bigger fan, new cap, new thermostat, and rad is full. Have to keep the truck at 90 km/h (55 mph) ot it will overheat. In summer, of course. The L6 is a long engine and the temp sensor is at the back - far from the water pump. Is this part of the problem, or is it really prone to overheating?
__________________
Present: 2015 Tacoma. Yeah, not a GM, but I love it. 1969 GMC 32,000 - fix, drive, relax, fix... 2019 BMW R1250 GSA - Yahoooooooo 1979 Honda GL 1000 - retro touring at its best. Past: '05 Sierra 4x4 - Had 270,000 KM and running well when it was written-off by a stop sign runner. '94 F-150 from the "F word" company. I'll admit it...good truck. Sold what was left of it for $800 to a guy who came to pick it up at 11:00 PM with cash in hand. Hmm. '79 Sierra Grande (Black) organ donor - perfect rebuildable 4-bolt 350 and a good TH350. '76 Sierra Grande (Orange) - hate isn't too strong a word. Kid who bought it turned it into a hot rod. '68 C-10 R.I.P. - Dad's old truck...too far gone to resurrect. '59 C-50 - with hoist. Truck is gone, wife isn't. Nuff said. |
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03-02-2024, 11:18 PM
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#2 |
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Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,515
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Re: L6 - 250 Overheating
Is it really overheating or is the rad seeking the right level.
You don’t fill the rad full. Usually about 1 1/2 inches from the top. |
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03-03-2024, 05:49 PM
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#3 |
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Moderator
 
Join Date: Jun 2017
Location: Cherryville, NC
Posts: 2,156
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Re: L6 - 250 Overheating
Check the water flow rate in the radiator....
sounds like a clogged core or water pump vanes have rusted away.... 
__________________
Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox 
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03-05-2024, 04:37 PM
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#4 | |
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Registered User
Join Date: Apr 2002
Location: Manitoba, Canada
Posts: 663
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Re: L6 - 250 Overheating
Quote:
__________________
Present: 2015 Tacoma. Yeah, not a GM, but I love it. 1969 GMC 32,000 - fix, drive, relax, fix... 2019 BMW R1250 GSA - Yahoooooooo 1979 Honda GL 1000 - retro touring at its best. Past: '05 Sierra 4x4 - Had 270,000 KM and running well when it was written-off by a stop sign runner. '94 F-150 from the "F word" company. I'll admit it...good truck. Sold what was left of it for $800 to a guy who came to pick it up at 11:00 PM with cash in hand. Hmm. '79 Sierra Grande (Black) organ donor - perfect rebuildable 4-bolt 350 and a good TH350. '76 Sierra Grande (Orange) - hate isn't too strong a word. Kid who bought it turned it into a hot rod. '68 C-10 R.I.P. - Dad's old truck...too far gone to resurrect. '59 C-50 - with hoist. Truck is gone, wife isn't. Nuff said. |
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03-06-2024, 07:49 PM
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#5 |
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Moderator
Join Date: Jun 2017
Location: Cherryville, NC
Posts: 2,156
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Re: L6 - 250 Overheating
Here is a link to a previous post about overheating 6's....
https://67-72chevytrucks.com/vboard/...d.php?t=706872 Most suggest moving the sensor to the thermostat housing....also, did you burp the heater core?
__________________
Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox
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03-07-2024, 12:11 PM
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#6 |
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Active Member
 Join Date: Jan 2015
Location: central oregon
Posts: 138
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Re: L6 - 250 Overheating
I just redid my whole inline six 250 cooling system like you. New 3 row radiator, 13lb radiator cap, fan shroud, heater core, water pump, fan clutch w/7 blade fan, 190deg thermostat, upper/lower hoses and heater core hoses. My temp sender is in the head about #2 cylinder up top. I thought it was running hot at first as the gauge reads about 2/3 to the hot. No where on the block with laser temp gauge have i ever been able to crack 190deg. Every time i shut truck down it has dribbled a tad bit of coolant to the point were it now sits 1 1/2” below the radiator cap. I just got a coolant tank reservoir to remedy that. But all has been well so far.
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03-14-2024, 03:32 PM
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#7 |
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Senior Member
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,049
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Re: L6 - 250 Overheating
That's funny, you're having L6 cooling problems in Canada, while my 292 L6 runs better in Tucson summers.
They are almost aircooled. Things I'd look for: -Thermostat -Coolant mix -Hoses and hose clamps -Water pump -Oil level
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
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