Datsun Roadster Forum-311s.org

Yes, it's me again. Now that I'm done with the BAR, I will dedicate to getting my baby ready for Solvang..........so I have a new problem. I started the engine a week or so ago, and have done it a few times after that without any problem other than the water flow.....As I check the temp. gauge, it shows the temp raising quickly, and I am forced to shut down with fear of heat-damaging the engine.

I put a new temp sending unit, and a new thermostat, but the thermostat is not opening at all no matter what temp the gauge shows.......what are my possible problem areas?

Jorge

Are you sure that the temp is actually going that high? If the thermostat won't open, then it is not reaching the operating temp. Is this a 1600 or a 2000? Did you "burp the system" on the 1600? If it is a 2000, do you have the bypass bleed on the waterneck? (only the OEM type necks had those - the 240Z version does not) So many questions to get us there...

Oh yeah, when you put the thermostat in, did you put the spring side towards the inside of the head? A fairly common issue is to put them in upside down. The spring SHOULD point towards the inside of the head - not towards the radiator....

Jorge0227 wrote:...what are my possible problem areas?

You might want to also check the gauge. You'd have to do a little rigging, but put the sensor in (at least recently) boiling water and see what the gauge reads. You'd have to supply the ground to the sensor, but a piece of wire wrapped tightly around the body should be enough grounding to work.

-and-

spl310 wrote:"The spring SHOULD point towards the inside of the head - not towards the radiator..."

Or in other words, for the R16, the spring should be down.

Ok......what is burping and how do I do it? Now, I installed the thermostat with the spring facing down (inside the head). The sender is new as well. And the gauge starts as if it was "cold", and immediately, and slowly, starts raising to the 250 degrees. In less than 3-4 minutes its all the way there!

It is a 1600.....and I don't see any indication of the pump(which is new as well) pumping. However, the water reached the heater valve...I know this because I had a small leak there for a bit.

Jorge

OK, now we have something to work with! Burping is easy! Just get a burp cloth and put it on your shoulder, put the baby on your shoulder - oh, wait, you meant the car, didn't you....

To burp it, take a long screwdriver and gently push the thermostat open. This will let the air escape. You can only do it on the 1600 with the OEM water tower. If you changed to the water neck from another car, you can't do this.

If the temp truly is climbing that fast, there is another issue somewhere. How does it run?

Sid:

I like people with good sene of humor! Now, I have the original tower, so I push gently while the engine is running, or off? This thing makes sense, because I had a Honda some years ago, and it had on the head, and actual "bleeder" to let the air out of the cooling system in cases where the block had to be refilled with coolant and/or water........I'll give that a try first and see what happens.

But before I do it, I assume I "burp" it with the engine running, before it gets too hot, right?

Jorge

I believe you'll fill cold with the engine off.

What is ging on is that the thermostat is blocking water from going down when you're trying to fill it up.

Take a long screw driver and press down gently on the thermostat's spring valve to open it up. Try not to break or bend it.

Now, with valve open pour in the new fluid/water mixture right down into to it to a complete fill

This should allow the water pump to now generate that unducted flow neccesary for the system work.

I am not sure about the water needing to running. It seems to me like trying put in fluid with a radiotar cap open. The fluid expands as it gets hotter defeating the purpose.

It doesn't need to be running, you're just trying to get any air trapped in the head out.

Gentlemen: I "burped" the baby, and eventhough air bubbles were released and it swallowed some more coolant, it is still showing the temp raising to 250 degrees. But I still don't think an engine can go up like that in 30-45 seconds.

If the temperature was indeed so high, then the thermostat should have oppened, right? But when I touch the radiator hoses, they're both COLD, as if nothing came from, or left to the engine. Even the cap and water in the thermostat housing are cold as it was before the engine ran for a good two minutes.

I am frustrated!

One more thing...... I know that the fuel and temp are hooked to the same volt. reg.......and my fuel tank is not connected or wired yet. Will this affect the temp gauge?

Hello Jorge,

I'm not sure if not having the fuel sender hooked up may alter the temp gauge. It is possible, but I doubt it...

From what you have added in the last few posts, I think you have a gauge issue, not a over-heating issue. If your engine was to heat to 250 in 30 seconds of idling, it would require half of a fuel tank's worth of energy!

I would try checking the gauge circuit.

I would bet that you get the same gauge response with the ignition on and the engine not running???

My first test would be to hook a line directly from the sender to the gauge (run a new test wire, don't use anything in the harness), then attach another new wire from the gauge to the regulator (make sure you are on the correct side of the regulator) and connect the regulator to 12V+. Try just turning the ignition on and seeing if the gauge stays at the left. If so, try warming up the car...

If that doesn't do the trick, then there is something wrong with the sender, gauge, or regulator... TR

TR: Thank you for your contribution to my quest for help! I will try this tomorrow, and then will let you know the outcome! When you say to attach to a 12+, you mean the battery, or where? And regulator, you mean the small temp/gas regulator?

Jorge

No problem!

Yes, the 12V+ can be directly from the battery and the regulator is the little one near the steering column. I do not know if the regulator has to be wired a certain way (if there is an "in" and an "out"), probably not, but it might be worth trying it each way (swap the leads on the regulator terminals)...

Also make sure the engine has a good grounding strap, etc...

TR

A little while back I was tracking down a gremlin that poped up and managed to get the wires for my fuel gauge and temp gauge swapped on the relay under the dash. It caused both gauges to do some strange things. you might try swapping the wires on the relay that sits just under the steering colum. Not sure if thats your problem, but it is worth a try.

Will