diagnosis confirmation

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dads311
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diagnosis confirmation

Post by dads311 »

I have been getting braver and braver driving my car, getting all the bugs fixed as they come up. I have a new one I noticed the other day, my temp gauge was reading about 220 or 230 degrees. I got it back home and got my digital laser thermometer and the head temp was 175 degrees. There was no boiling sound or coolant running on the floor.
I do have a new aluminum radiator with electric fan and a fresh motor and head. I did use a sending unit that was in one of the boxes of parts so it may be 50 years old. I also followed the wiki and built a gauge voltage regulator and my fuel gauge is working spot on.
Today I drove it for a ways and the temp got up to about a needle width past the 190 mark. Again I got it home and used the digital laser thermometer and the readings were: head on the passenger side 144, head on the driver side 153, thermostat housing tower 154, lower rad hose at radiator 137 and the upper hose at the rad was 150. These readings were after it had been shut down for about 5 minutes. Oh yeah it does have a new 180 degree thermostat, not that that means much. I even jacked the front of the car up when adding coolant and kept squeezing the lower hose to burp it to make sure it was full.
I suspect I need a new sending unit but is there something else I need to check. I promised my self I wasn't going to spend money on the Datsun this month because the other cars are feeling way neglected but I can't stand driving it with the gauge sitting so high. I really don't think it is over heating but seeing the temp gauge at 220 in a new motor is a scary thing.

If you will let me I want to say a huge Thank You to the members of this board. You have been a great help in the restoration of this car even if you didn't know it. I revealed it a couple weeks ago to my brothers and sisters and their families and got lots of OOOhs ans awwwwes but when my brother told me Dad would have been so happy to see his little car in this shape again I almost lost it. Then about a week after that I took it to a car show and the interest in the Datsun was crazy and it is interesting how many people had one in their younger days. Anyways thanks again and I am just glad the worst is behind me now and I just have some little things to work on over time. I think I still need your collective minds to keep this thing going so keep up the good work.
Mike
rebuilt dads 67.5 1600
1952 GMC 302ci 6cyl w/cam and 3 deuces
1965 Mustang (Wife's)
1971 Nova (Son Claimed)
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Linda
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Re: diagnosis confirmation

Post by Linda »

It's hard to get all the air out. You can think you do but often you don't(I didn't) So, multiple purges are perhaps needed.
Also I have a mechanical temp guage which gives an accurate temp, much better than the stock . Available thru Summit.

Linda
Sadly-Linda has passed away 2022. She was the 311's den mother and drove the first Rare-Parts ball joint project. RIP.
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Nissanman
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Re: diagnosis confirmation

Post by Nissanman »

dads311: If you have satisfactorily determined that the gauge is reading high you can adjust the internals to make it accurate.
There is a hole behind the gauge through which you can move a toothed wheel device to fine tune the needle deflection.
I have done this on my '65 and if you do a search, I know some others on this Forum have followed suit.
Always a good idea to use an external independent temp. sensor to verify suspected over heating issues, you've done well ;)
Nissanman, just trying to help.
1965 SP310 Engine No. G-93326 Car No. SP310-10817
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dads311
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Re: diagnosis confirmation

Post by dads311 »

Linda and Nissanman thank you for the responses. I guess I will look to see what is involved with getting behind the gauge to fine tune it. this is a 67.5 so it has 2 gauges in one housing and 3 screws that hold it in. May be very interesting, it may be easier to just get a new sending unit, but I'll see what happens.
Thanks again
Mike
Mike
rebuilt dads 67.5 1600
1952 GMC 302ci 6cyl w/cam and 3 deuces
1965 Mustang (Wife's)
1971 Nova (Son Claimed)
Jdflyer
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Re: diagnosis confirmation

Post by Jdflyer »

You can always test the temp sensor to see if it is reading correctly. You will need an ohm meter, candy thermometer, pot of water on the stove, and temp to resistance table.

1. Connect temp sensor to ohm meter
2. Set ohm meter to 20k resistance.
3. Put temp sensor in water.
4. Note temp and resistance.
5. Turn stove on and increase water temp by 50deg
6. Repeat 4&5 through testing range.
7. Compare resistance with actual table.

Room temp aprox.... .385 ohms
130 degrees.............105 ohms
190 degrees.............45 ohms
220 degrees.............32 ohms
240 degrees.............25 ohms
1970 SPL 311-29311
Phoenix, AZ
Jdflyer
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Re: diagnosis confirmation

Post by Jdflyer »

To calibrate the gauge use a 45ohm resistor to replace the temp sensor and then tune the gauge to 190 degrees as mentioned above
1970 SPL 311-29311
Phoenix, AZ
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dads311
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Re: diagnosis confirmation

Post by dads311 »

JDflyer Thank you for the information. I will do that.
Mike
rebuilt dads 67.5 1600
1952 GMC 302ci 6cyl w/cam and 3 deuces
1965 Mustang (Wife's)
1971 Nova (Son Claimed)
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dads311
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Joined: Sun Dec 04, 2016 9:24 pm
Location: Emmett, Id.
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Year: Low Windshield-64-67.5

Re: diagnosis confirmation

Post by dads311 »

Update: My sending unit was toast. Got a new on and now my gauge and laser thermometer agree on the temp. Thanks for the help.

Mike
Mike
rebuilt dads 67.5 1600
1952 GMC 302ci 6cyl w/cam and 3 deuces
1965 Mustang (Wife's)
1971 Nova (Son Claimed)
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