Cooling Question

[mdbrandy]

Originally posted by 78 280zcar

after the car is warmed up you can see it flow inside of the radiator cap. Any suggestions on the thermal transmitter?

I think Carl's point is that while you may be seeing flow, it may be only half the flow that is supposed to be there due to plugging of the radiator tubes. No way you can tell by just looking. Heat transfer in an air-to-water heat exchanger like the radiator is highly dependent on heat transfer area (as well as velocity, surface conditions, and other things), so half the flow would be at most only half the heat transfer. Maybe at idle that half flow is fine, but at speed, the engine's heat output outstrips the radiator's (degraded) flow ability. Bottom line is don't discount the possibility of degraded radiator flow due to plugged tubes.

Wish I could help you on the sender. Don't know that one.

[Bambikiller240]

Originally posted by 78 280zcar

after the car is warmed up you can see it flow inside of the radiator cap. Any suggestions on the thermal transmitter?

That tells you almost NOTHING about the condition of the radiator! All that tells you is :

1. the Thermostat opened and is allowing coolant to flow to some degree.

2. the water pump is pumping coolant to some degree.

3. the radiator is not 100% COMPLETELY plugged up. (Radiators almost never get plugged "completely" because the car starts to overheat long before things get COMPLETELY plugged)

NOTHING ELSE!

What you see is "some" amount of coolant being pushed by the pump. It can only "push" as much coolant as it can "suck" from the engine block. If the radiator is partially plugged , the pump cannot "pump" the full volumn of coolant needed to properly cool the engine. You cannot see and measure the volumn (quantity) of water being moved. The volumn of coolant being moved through the radiator is one major key to cooling your engine. If the radiator is plugged such that a sufficient volumn of water cannot flow through the radiator to be cooled quickly enough, then your engine will overheat.

You cannot tell if the radiator is plugged by looking at it. A Radiator shop must open it and examine ALL of the tubes in the core.

Can't healp with the transmitter, I just replace mine when I am sure that everythin else is in good condition and the guage reads funky. It is a simple device and seldom fails.

*Spent 5 years working in a Radiator shop repairing and recoring all sorts of radiators, in my youth. Radiators have operated on the same principals since first used in automobiles.

[78 280zcar]

The thermal transmitter is to the right of the water temperature switch and only has one wire going to it instead of two, it is part of the water temperature gauge and the oil pressure gauge system. If I cant find anything out about the transmitter, or if anyone cant help on that, then I am going to take the radiator to a shop and have them route it out for $55.00. I guess that isnt bad, I would rather pay that much rather than having to buy a whole new engine block, ya know :classic:

EDIT: I guess we posted at the same time bambiker, but I wasnt saying that you didnt know anything about what you were saying about the radiator, I was just a little more concerned about the reading I got on the transmitter. Someone told me I could check for flow that way.

[Bambikiller240]

The transmitter is a simple thermocouple. They very seldom fail.

More than likey it's a part of the cooling system itself that is the problem. Since you have a relatively new pump and T-stat,and fluid coupled fan, the radiator is the next logical (and most likely to fail) part to have checked.

$55 is cheap for a Rod-Out. Here in the Bay area you'd pay $90

[78 280zcar]

About the transmitter, I tested it like it said in the book and it failed the test! Also what is the oil pressure gauge suppose to do. Mine hardly does anything at all, when the car is idleing the gauge will go up just a little, and when I step on the gas peddle and get the RPM's up to about 2000 it goes all the way back down, is this normal. Thanks for the help. I just need to know if I have to go to pick and pull because I cant find this part anywhere not even in motorsport z's. I would have to order it from Nissan and that is way to expensive, seeing as I am on a tight budget

[mdbrandy]

Originally posted by 78 280zcar

Also what is the oil pressure gauge suppose to do. Mine hardly does anything at all, when the car is idleing the gauge will go up just a little, and when I step on the gas peddle and get the RPM's up to about 2000 it goes all the way back down, is this normal. Thanks for the help. I just need to know if I have to go to pick and pull because I cant find this part anywhere not even in motorsport z's. I would have to order it from Nissan and that is way to expensive, seeing as I am on a tight budget

Doesn't sound normal. In my '78, when the car is cold, the oil pressure guage is maybe 1/4 of the way up at idle, and 2/3 of the way up when I am driving. Once the car warms up, the idle pressure is a little above the bottom mark, and the running pressure is something around half way.

Which part can't you find? The sending unit, or the guage?

The problem is more likely the sending unit. I know Chloe (MidwestZ) can get those - the NOS Nissan ones are over $50, but there are aftermarket ones too that are cheaper. I have no experience lately buying and installing one, however.

[78 280zcar]

The part that I cant find is the water temperature thermal transmitter, it has a one wire hookup like the sender. That is what it is called in the manual I have. It says in the manual that it is part of the water temp gauge and the oil pressure gauge. If you read the other posts I have on here, I wrote how to test it and it gave a bad reading.

[78 280zcar]

It is called the water temperature sending unit and I found it for 12.95 in motorsport magazine. Sometimes I swear I am a blond airheadLOL

[Bambikiller240]

Originally posted by 78 280zcar

About the transmitter, I tested it like it said in the book and it failed the test!

No, you did not "test the transmitter"! You disconnected it, and it was no longer connected to ANYTHING!

The test you performed is meant to determine what is causing a false "temperature reading" at the guage when the cooling system is operating correctly yet the guage shows an incorrect reading,

You disconnected the transmitter from the wiring and grounded "the wiring". All you did was test that the guage and the associated wiring reactedto "grounding" as they should. Thus proving that IF everything else in the system is working properly and the system IS cooling the engine properly (yet the guage still shows a high/low teperature reading) that the transmitter and NOT the guage or wiring is the problem. Thus by process of elimination, the transmitter would be the problem. The test is meant to be performed when the cooling sytem is in good order yet the guage reads incorrectly in order to determine which part of the temperature reading system is a fault.

[mdbrandy]

Originally posted by 78 280zcar

The part that I cant find is the water temperature thermal transmitter, it has a one wire hookup like the sender. That is what it is called in the manual I have. It says in the manual that it is part of the water temp gauge and the oil pressure gauge. If you read the other posts I have on here, I wrote how to test it and it gave a bad reading.

That has nothing to do with oil pressure. That is a separate sending unit on the right side of the block down by the oil filter.

[78 280zcar]

Thanks for all your help guys, I am going to get a new oil pressure sender and get my radiator routed out and see if that helps with the cooling issue. Shane

[Bambikiller240]

Good Luck. Let us know how it turns out.