Cooling issue with 521, maybe

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jayden71
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Cooling issue with 521, maybe

#1

Post by jayden71 » Mon Jul 01, 2013 7:39 pm

So,like I posted earlier in insomniacs, drove the truck in 111 degree heat today. Stop and go traffic for about 40 minutes. Never going over 40mph. My temp never got over 190.
That seems just fine since I have the water shut off to the heater core because the control knob in the cab is broke.
My concern is when I take her on the fwy up to speed, 60-70mph. If its more than 80 outside temp she seems to run rather warm. At 70 I;m turning 3850 or so.
I;m concerned because she has never done this before and to me seems kinda backwards. Wouldn't she run hotter in stop and go especially in this heat??

I may be making too big a concern over it, I dunno...looking for some input here.

Stock L16 with a U67 head. Made the move from Baker to Boise last July in 95 degree weather with 800 pounds of stuff in the bed and she never went over 195.

Here is where she runs at fwy speed

Image

I have replaced the thermostat since the old one was sticking and not opening at the right time.

The gauge is mechanical and was replaced this winter.

Am I just bein too cautious?
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flatcat19
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Re: Cooling issue with 521, maybe

#2

Post by flatcat19 » Mon Jul 01, 2013 7:49 pm

U67 head-no cooling ports in a head known to run hot.

L16-no fan clutch. Idling gets the same fan speed as hauling ass.

Now combine the two.

Just a thought.

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jayden71
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Re: Cooling issue with 521, maybe

#3

Post by jayden71 » Mon Jul 01, 2013 7:55 pm

flatcat19 wrote:U67 head-no cooling ports in a head known to run hot.

L16-no fan clutch. Idling gets the same fan speed as hauling ass.

Now combine the two.

Just a thought.
Good thought.

Thank you, never thought of the no cooling through the head.
DRIVEN » Tue Nov 04, 2014 6:30 pm wrote:I think Bill might be gettin laid.
Ni10 » Wed Nov 19, 2014 7:56 am wrote: all Datsuns ran when parked.

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Re: Cooling issue with 521, maybe

#4

Post by datsunmike » Mon Jul 01, 2013 8:11 pm

The water passages in the intake are to regulate the temp of the air going through them. When the motor starts up cold (specially in cold weather too) The warmed water helps vaporize the gas droplets. The motor runs better sooner. In extra hot conditions idling, slow traffic with high under hood temps the water helps 'cool' the intake from radiated heat from the exhaust manifold. This prevents boiling gas in the carb, vapor lock, pinging.

Coolant in the intake or not shouldn't cause it to run hot. After all the U67 head didn't have the water in the runners did it.

The $10 dolla fix. Buy a new thermostat. Yes you have a new one... could be bad and before chasing other more expensive remedies try that. Could be a $10 fix. No harm done, if not, you have a spare for testing next time.

If not...
Check for a soft lower rad hose. Rev it way up and look and see if the hose collapses from the suction.

Above 30-40 MPH you don't even need a fan as enough air is forced through the rad from vehicle motion. If overheating and you know you have enough air flow then maybe the rad cores are getting plugged.
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Re: Cooling issue with 521, maybe

#5

Post by wayno » Mon Jul 01, 2013 8:13 pm

Mine runs hotter on the freeway when it is hot outside(over 85 degrees), and when I get off the freeway and hit a signal light, the SU bowls start to boil, and cause a temporary miss till they cool again when I get moving.
I wouldn't worry to much about it unless it gets worse.
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Re: Cooling issue with 521, maybe

#6

Post by jayden71 » Mon Jul 01, 2013 8:14 pm

Hmmm, ok.

Staring simple and cheap is more appealling
DRIVEN » Tue Nov 04, 2014 6:30 pm wrote:I think Bill might be gettin laid.
Ni10 » Wed Nov 19, 2014 7:56 am wrote: all Datsuns ran when parked.

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Re: Cooling issue with 521, maybe

#7

Post by jayden71 » Mon Jul 01, 2013 8:17 pm

wayno wrote:Mine runs hotter on the freeway when it is hot outside(over 85 degrees), and when I get off the freeway and hit a signal light, the SU bowls start to boil, and cause a temporary miss till they cool again when I get moving.
I wouldn't worry to much about it unless it gets worse.
I don't have SUs but as soon as I am off the fwy at the offramp light she cools right back down to 190 or so. Has never boiled or gone over what it shows in that pic
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Re: Cooling issue with 521, maybe

#8

Post by flatcat19 » Mon Jul 01, 2013 8:20 pm

My green 521/all stock, ran hotter when moving. Cooler when idling or slowly putting through town.
Can't say for the blue one. I blew that shit up 3 hours after I paid for it!

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Re: Cooling issue with 521, maybe

#9

Post by jayden71 » Tue Jul 02, 2013 9:25 am

May have found the issue! :thumbs:

Bottom rad hose slightly kinked where it bends to go over alt.

Thanks DMike!!!!

Got a new one layin around so, gonna slap it on and see what happens :)
DRIVEN » Tue Nov 04, 2014 6:30 pm wrote:I think Bill might be gettin laid.
Ni10 » Wed Nov 19, 2014 7:56 am wrote: all Datsuns ran when parked.

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Re: Cooling issue with 521, maybe

#10

Post by datsunmike » Tue Jul 02, 2013 3:09 pm

You may be able to trim one end shorter and this will lift it slightly. Think twice cut once.
My Datsuns, like good friends, have never let me down. At least in any way that was not understandable and thus fixable.

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Re: Cooling issue with 521, maybe

#11

Post by jayden71 » Tue Jul 02, 2013 3:32 pm

I found a hose in my stash
Not the preformed one
the type with the spring in it
In really good shape. Slapped it on, but have not had a chance to go for a drive.

The wifey came home and then we took her car to the store.

The hose I took off was getting soft in that one spot sooo hoping this was the issue.
Will drive her to work tomorrow and on the way home gonna hop on the fwy.
DRIVEN » Tue Nov 04, 2014 6:30 pm wrote:I think Bill might be gettin laid.
Ni10 » Wed Nov 19, 2014 7:56 am wrote: all Datsuns ran when parked.

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Re: Cooling issue with 521, maybe

#12

Post by izzo » Tue Jul 02, 2013 4:56 pm

my upper and lower rad hose are soft. tho I think the lower one has a spring in it, could be wrong.
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Re: Cooling issue with 521, maybe

#13

Post by datsunmike » Tue Jul 02, 2013 6:15 pm

The top one is under pressure from the pump so it won't collapse, though if really bad it may split. The bottom one is on the suction side of the pump.
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Re: Cooling issue with 521, maybe

#14

Post by jayden71 » Wed Jul 03, 2013 12:04 pm

Ok so, on the way home from work today hopped on the connector then the fwy. 72mph and had 5 40x40 pallets in the back :lol: . 99 outside and cruised like that for about 5 miles. Only got up to 190. That's with the heater core shut off still. Good news to me, seems to be back to normal. Would like to take it out to my parent s house 40 miles away for a good test but, so far so good.
DRIVEN » Tue Nov 04, 2014 6:30 pm wrote:I think Bill might be gettin laid.
Ni10 » Wed Nov 19, 2014 7:56 am wrote: all Datsuns ran when parked.

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