Datsun Roadster Forum-311s.org

Hey everyone,

I got my fueling issues figured out which seemed to be the wrong pump, wrong filters, and wrong mounting location for the pump. After some great input I got it all sorted out and the roadster is purring like a kitten!!

Over the last few weeks, and even more so I noticed this along with the fueling issue, I'm having a weird cooling situation. I'm letting the car warm up for a few minutes before driving, then once I take it out, the temp gauge raises to a little over 220 then after about 30 seconds to a minute goes right back to 190. If I'm not driving, I'm having the temp raise on a some what regular basis. I have a new ebay radiator, new thermostat, new hoses, and no leaks in the system based on no leaking once it's at operating temp.

I was doubting the installation of the thermostat, wondering if I could have put it in upside down, but that is not the temp.

I took an infrared thermometer to the coolant tower, radiator, and hoses today and found the thermostat sending unit housing to be sitting at 220, the cooling tower at 190, the radiator at 105 at its hottest point, although the top of it was very hot to touch so I'm not sure if that's an accurate reading. Readings along the front of the radiator was typically 70-90, and it felt room temp in most locations to the touch.

When I got the car I did not replace the water pump, and am wondering if I'm not circulating coolant like I should at this point. Every now and again, especially after idling in place for a while, I'm having coolant expelled form the expansion tank.

Mike

Sounds like it is not flowing well , the core should be hotter than 90. you say . 1st fill with a above engine fill funnel
A cut off big trans funnel works ' then run at fast idle in the driveway . if its running 220 its going to throw up out the funnel so watch out
A Rod out of the radiator core would be recommended or new ( many a rad tech lies about doing it tbough)
Normal fan on it ?
Water pump impeller may be loose or off

It's a brand new radiator, and the fan is stock, seems to be pulling plenty of air through.

Lots of people try to fix leaks with stop leak products and feel that if a little doesn’t work than I bunch might. I admit, I was one of them in my younger dumber days. Those products, when used in abundance and then left in an non used engine for years can completely block off a water jacket. It sounds like you are not getting good flow out of the radiator. Try disconnecting the upper hose and run the car with a hose feeding the radiator to see what kind of flow you are getting out of the thermostat.

Have you bypassed the heater and manifold water flow? We see this on the race car. The head is getting hot before the thermostat opens. Soon as the thermostat opens it cools back off. Drill a <>3/16" hole in the flat part of the thermostat.This will allow enough water to bypass and the engine will warm up more evenly.

keith0alan wrote: ↑Mon Apr 27, 2020 9:00 am Have you bypassed the heater and manifold water flow? We see this on the race car. The head is getting hot before the thermostat opens. Soon as the thermostat opens it cools back off. Drill a <>3/16" hole in the flat part of the thermostat.This will allow enough water to bypass and the engine will warm up more evenly.

I have a thermostat that has a 1/8" or so hole in the flat part. Should I make this a little bigger to allow slightly more coolant through?

Nothing else has been bypassed, but it does sound like there is a delay in having the thermostat open up as you mentioned. The valve to the heater may be closed, I haven't made it that far yet though.

I went for a couple drives today and had the same temp thing happen, although I have had no loss of coolant. I'm going to pick up a block test kit from Napa in the next day or two and see how that goes.

I have pulled that vent check valve off and it takes 5 -8 x longer for the thermostat to open fully on an eclipse. I would not

Check the hose to the manifold and see if it warms up right away. If the three way valve is clogged or turned into an "off" position then the water will not circulate properly.

before you buy that block test kit,there is an old ,fairly simple,and if there is combustion gasses in the cooling system,pretty affirmative test.If you have a 1600 motor,drain coolant just below the t stat level.remove water pump belt,and t- stat. With a cold motor,overnite if possible,run for a few minutes. If you are observing a fair amount of bubbles this could be a positive. I have used the chemical test often in past working situations,and contamination of test fluid was often a problem.Had an old time mechanic show me this ,and has proven to be a good test in the past.The 1600 lends well to this test as the t-stat sits in a horizontal position.Again,completely cold motor,and water pump belt off.Doesnt need to run long.
just my 2 cents

I'm back to the drawing board with some fueling issues I've been experiencing. I do know for a fact that I have not had a drop of coolant leak out of the car unless I'm experiencing the sputtering. If I drive the car around town and get it up to temp it's not having any overheating issues or coolant loss. Once I get the car on the road for 20+ minutes, I experience the sputtering, then the overheating and some coolant loss through the overflow tank.

I found another thread that's a solid 5 years old that I've resurrected and will see if I can get some answers from that thread.

Pull the thermostat out and reconnect
With frt. Of car on a slope up fill. radiator. Now should be able to feel flow. And drive
Also they make a 1.5 clear vinyl hose that you can see the coolant flow
Has to be either ...W pump impeller is off - no pump
You have air in the motor trapped at rear - the w pump pumps fluid not air. Why the high fill funnel needed
Radiator tubes mostly blocked. You said new ...so
Radiator air flow blocked unlikely

Well here’s the good news. I was able to figure out what the issue was after a positive block leak test.

Looking at options now for fixing the 1600, upgrading to a stroker or 2000, or go with an SR like I had originally planned for the car.

Gonna be an interesting next few days or weeks while I figure this out.

What was the cause of the problem?
Linda

I had a positive block leak yesterday and found exhaust in the coolant. I’m evaluating options now.

autoairman stated

I have used the chemical test often in past working situations,and contamination of test fluid was often a problem

I had this problem too until I did the test correctly. Sure the tester was not touching the coolant?

Linda