Datsun Roadster Forum-311s.org

Those who report temps of 120-140 are probably running without a thermostat. I ran without one for a while at about 140. But as soon as I hit the highway the temp would fluctuate wildly. (probably not real good for the engine). I then put in the thermostat but in the process of "burping" it, it got stuck open without my knowing and it ran about 150 most of the time due to the somewhat restricted water flow probably.

Now that I have a correctly functioning stat it warms up nicely to about 170, stays there until I hit the highway and start revving to about 4-5000 and then it stays about 190-200.

Why it would run hotter on the highway is maybe a result of more internal friction/combustion?

Well, Dave, I agree with you and John, so that nixes Item 7 on your list.

Damn, another good theory shot to hell.

you can test your thermostat by dunking it in boiling water (i cant recall for how long, maybe somebody knows) and if it opens up at the right time then it works. But the thermostat is mainly used for regulating a minimum temp. ie if the engine is cold the thermostat will be closed and the cooling system is not doing any thing. but if your thermostat is operating correctly and the engine is running hot then it means that your radiator is not cooling properly. this could be due to a lack of airflow, weak water pump, or your radiator needs to be cored. If you have done any modifications to the engine for increased horsepower you may need to look into a larger or possibly aluminum radiator. i hope you figure it out.

All,

Everyone is on the same page. The T-Stat in boiling water is a great way to weed-out defective " NEW" T-Stat's...yes new one come out of the box not work as they should. Use a meat thermometer in a clear Pyrex bowl, hang the T-Stat from the top in the water. Start the burner on the stove a watch the temp. rise, and record the opening and closing temps as it cools, a few ice cubes make cooling quicker. Do this a couple of times to make sure the Stat works every time.

I have just installed a 4 blade NOS fan with the spacer, in place of my 7 blade clutch fan on a U20. This was a factory TSB fix back in the day. The factory air scoop also helps bring cool air into the lower radiator tank area.

I have installed metal plates with holes cut in the center on my race cars, in place of the T-Stat. This assures you of a good steady temp at speed, while giving you enoughh back pressure to let the radiator do its job.

Two cents,

Enjoy,
JC

Wow, someone else has heard of the restrictor "washer" in place of the thermostat!! Tomorrow's project for me is to take out the "good" radiator i got to see why the top is really hot and the bottom stone cold without even a fan running. I don't think it's that efficient! Hopefully won't need to recore. Anyone know someone who will recore a 2000 rad?

Also, can an aluminum core be put in? I'm guessing not, dissimilar metal corrosion and all that scientific stuff.

You can replace the entire radiator with a Del Sol unit. For a very good price, you can get a radiator that outperforms the stock - there's no comparison in the performance, longevity, etc...You will need to fab brackets, though.

As for the "coolant traveling too fast" theory... A car may run cooler with a restrictor or tstat, but it is not because the coolant is flowing slower. It does not take any time for water and metal in intimate contact to transfer heat. I think everyone can come up with many examples of this. Think of bathtub, swimming and coffee experiences...A little less painful, stand in front of a fan on a hot day, set it to low, then high...

I wonder what other factors may be at play, though. Possibly cavitation or poor mixing of the cool and hot fluid in the water jacket...

Spyder

Don't run an electric fun, they are a pain and I have not had good experiences with them. Ditch the 7 blade fan and go for a solid mount 4 blade. Cools great and doesn't give you any of the noise.

I just went through the whole radiator rebuild route. By the time you get a nice new 3 section core and the radiator all rebuilt you can be into it for almost $300 (fees vary by area). I just bought and all aluminum (plastic top and bottom tank) del sol radiator brand new, shipped to my house for $50. It also came with a radiator cap. You can't beat it! And it is more efficient over the rebuilt radiator.

Check Ebay for the radiator

This discussion is great - I was just after some averages but this is much more enlightening! The thing is though, I can't help but arrive at the conclusion the the stock cooling system is an inherent design shortcoming in the roadster... I'm dreading summertime in Oz now without some serious work on the cooling system! It can get to 110 at Christmas time down here!

I already fabricated a spacer so I can use a generic American flex blade fan instead of the 7 blade. Plan was a low pitch 16' fan on the engine with electric for backup. The electric is in already, but having some issues with the temp sensor. Is the DelSol radiator just a bracket an bolt affair, or do I need to cut existing body stuff? Might be the way to go vs fixing the one I have.

I've never looked real closely at a Del Sol radiator install to see. I think it only requires brakets to be fabricated...

I haven't installed mine yet but I have seen one done and I think all you have to do is get the 3 rubbers that soft mount the radiator and make 3 small brackets.

Dave,

A hot top tank and cold bottom tank is usually a stuck T-Stat. A plugged core can also be the cause, but always go for the most common ( cheapest / easiest) fix first.

As far as the stock cooling system not being up to the task, I have to defend the little Japanese fellers who built these cars. I have a factory solex setup on my SRL, and I just had it out today with the new 4 blade NOS fan in 80 degree weather. It came up to temperature within 10 -15 minutes and ran rock solid at 150 degrees. My cooling system is stock, factory radiator, air scoop, hoses and pulleys. I use Super Long Life Toyota coolant, not that that matters, but this coolant is factory premixed so you don't need to add " hard" water to mix it.

JC

A properly maintained stock system is fine. The issue is that lots of times stuff is missing or has been dorked with. The scoops are almost always gone. The cooling systems are rarely flushed, and the mix on the coolant is a guess at best. On the 1600, you also have to burp the baby...