Datsun Roadster Forum-311s.org

On my 69 1600 the cooling system seemed to be running great. The temp gauge seems quite accurate and has been tracking at 50% of the way up.

Well, then I mess with a good thing....The overflow tank was completely full. When I checked the thermostat housing section, the fluid was down about 12-14 ounces. So I filled it up close to the top...

My concern is I filled it too full....Since completely filling the system, the temp gauge has crept up to about 70% of the way up the gauge. I'm thinking I have overfilled the system and have not left enough space for the liquid to expand....

Would over filling the cooling system cause the temp to raise? Have I overfilled the system?

Thanks,

Dan

Okay, un update....Just went out to the car (brought it to work today) and found the problem...the heater core started leaking...

So I need to bypass the heater core quickly. Seems that the winter/summer valve should be the easiest route.

Two questions:

1) to close the winter/summer valve, which way should the valve handle be facing? Right now the tip of the handle is facing forward towrds the front of the car. Adjusting the valve handle to point upwards should stop the collant flow to the heater core....correct?

2) The handle seems nearly frozen shut...Any suggestions on how to unfreeze the lever?

Well, if you overfill the system, it just purges the excess onto the ground. Most likely, the issue is that the water level was too low and the sending unit was in the air. I had that happen frequently. The coolant should be pretty close to filling the filler on the head, and the overflow likes to be about half full in my experience. BTW, make sure that the overflow tube is not clogged with dirt dobbers!

The valve will not completely bypass the heater core unless I am mistaken. Best to just disconnect one hose and reroute it to take the heater core completely out of the system.

Thanks, Sid.

Question:

"Most likely, the issue is that the water level was too low and the sending unit was in the air. I had that happen frequently."

So, if the sender is in the air, the temp will show High?, or Low?

I went ahead and bypassed the heater core as Sid suggested . The summer/winter valve is frozen shut anyhow...

Refilled the system, and things look okay for now. Just drove her for a few miles (for 15 minutes or so) and the temp gauge is reading just a bit above half-way. For those who have the later models...The needle is aligned with the 'degree' mark on the gauge.

Had a radiator shop check the temp several times with a temp sensor gun (infrared?) and at the head it was showing about 185.

Now for the clean-up of the passenger compartment when I get home...uggg...

My experience has been that the sending units that are in the air tend to read low. Often they read a normal temp when the engine is hot. ymmv

Sounds like the leak was your culprit.

Yep...the heater core was the problem. Drove 30 minutes in rush hour traffic...car stayed nice and cool...Back to normal.

But, there was a silver lining to this experience. When I took out the carpet from the passenger compartment to clean/dry...I found the floor board to be in terrific original shape.

http://groups.msn.com/BADROC/1968datsun ... hotoID=448

Yeup... I just had the same exact thing happen to my 4Runner last week.

I just replaced the hose. I amaze myself how my little hands can work in a 1 inch work space behind the engine between the firewall and underneath the EFI intake manifold.