What do you think about this reading on the temperature gauge? Is this too hot? 90 degrees outside. Thermostat housing reads 195 degrees with an infrared thermometer. Original radiator (2 row) that I had power flushed last summer. This gauge reads the same with or without the air conditioning on. Temp from the AC vents inside got as low as 35 degree on the highway with R134.

The temperature did not drop on the highway and the car runs great. Just installed a new 180 thermostat. Advice?

Edited June 16, 201311 yr by Burl

Burl: Looks about right for 90 degrees outside. But one always worries that it will go hig

If you are already running a 50/50 mix of water and anti-freeze/coolant - then add a bottle of Red Line Water Wetter to the radiator. That will usually bring the temp down 10 to 15 degrees. Also, if you are not running a synthetic oil already, you can switch to something like Mobil 1. That too brought my operating tem's down about 10 degrees.

FWIW,

Carl B.

Thank you to every one who has replied. In the winter (in texas) it runs normal. Fan clutch appears normal. I will try the "feel the radiator" approach.

Just put a traditional thermometer in the radiator when the gauge was showing the above reading and it showed 180 degrees. Also checked the fan clutch and it appears normal. My guess is the gauge is off!

Burl,

My cars have always ran dead center..Even in the west TX heat years ago. I have seen cars that run over the M and run just fine. Who knows whats wrong if anything is..

My thoughts,

Gauge is out of wack..

Could be radiator is clogged at the bottom and is only cooling 2/3 of what it can.

Fan clutch could be going out, but that would cost more of an overheating problem.

Your thermostat is way to high, I have always used a 160, 170, or none at all.

I would replace these parts in this order.

Thermostat (to a lower temp)

Gauge (used)

Fan clutch

Radiator

Just put a traditional thermometer in the radiator when the gauge was showing the above reading and it showed 180 degrees. Also checked the fan clutch and it appears normal. My guess is the gauge is off!

Burl,

Based on that it seems that the gauge maybe off. If I remember correctly, the coolant flows from the bottom of the radiator to the through the engine and out of the top, so the water at the top of the radiator should be the hottes - please correct me if I'm wrong. If you're worried about it still you could flush the radiator and see if anything comes out. When I first bought my Z and flushed the motor/radiator it was rather rusty and disgusting.

I live in Tucson and in the summer it normally get well above 100 degrees here and is rather dry as hell. As I expressed in the last post, I personally don't enjoy when the Z runs about 200 degrees. Its my personal preference nothing more. As 280~master posted I think your gauge might be out of wack, though your thermostat might be a bit hot for such weather.

Hope that helps

Jan

If I remember correctly, the coolant flows from the bottom of the radiator to the through the engine and out of the top, so the water at the top of the radiator should be the hottes - please correct me if I'm wrong.

Yep! Downflow. For the visual learners:

My car ran dead-center in the middle of the gauge on the hottest days with a 3 core 280zx radiator, and now that I have a dual electric fan assembly (out of a late 90s altima, $18 at the junkyard woo woo!) it runs about 1/3 of the gauge rock solid on 80 degree days, still haven't had a good 90 or 100+ yet here in Seattle since I did the swap though. (granted I have both fans wired to low speed, flick the switch over to dual high speed and I've got a hurricane under the hood)

Other relevant data, I've got hood vents that actually exhaust visible wavy hot air, so I've got even more cooling airflow than most folks anyways:

Sometimes I wonder if I'm the only guy out there with an early Z that actually runs cold

..... it runs about 1/3 of the gauge rock solid on 80 degree days, still haven't had a good 90 or 100+ yet here in Seattle since I did the swap though.

You may want to reconsider running those fans all the time. Due to radiational cooling overnight the engine block will actually cool below the dew point. This allows moisture to condense inside the block and drip into the oil. Contrary to popular belief, oil can absorb water up to about 1% by volume. Water in the oil reduces lubricity, promotes corrosion, and other nasty things.

Engine designers realize this and design the block to run 185 degrees F or higher. This temperature is sufficient to drive off the dissolved water. Running your engine so cold, besides thickening the oil, allows water to accumulate. There is no off-setting benefit running the engine that cold.

A few years ago in Tucson I had an overheating problem (due to an unrelated problem), went to the Nissan parts counter and asked for a 160F thermostat thinking it would help - the guy said it doesn't work that way and recommended a 180F which I am still running. The Z stays in the middle of the gauge even going up the mountains at 85 mph on a 105F day - but I have some other desert mods.

Seem to get more power when the Z is completely warmed up, based on freeway speed at steady RPM. 3500 rpm gives me about 79 mph on a cool morning, 83 mph on a warm afternoon, gauge reads 180F both times. I've rechecked it a few times. Maybe this could be partly due to temp in the AT and differential? Sometimes I wonder if it's running too cool.

195F seems slightly high, but I often got there with the stock radiator and no oil cooler.

You may want to reconsider running those fans all the time. Due to radiational cooling overnight the engine block will actually cool below the dew point. This allows moisture to condense inside the block and drip into the oil. Contrary to popular belief, oil can absorb water up to about 1% by volume. Water in the oil reduces lubricity, promotes corrosion, and other nasty things.

Engine designers realize this and design the block to run 185 degrees F or higher. This temperature is sufficient to drive off the dissolved water. Running your engine so cold, besides thickening the oil, allows water to accumulate. There is no off-setting benefit running the engine that cold.

djwarner, that is very well put. Many people overlook this fact and run thier car as cold as possible believing it will unlock some "wasted" horsepower. I've known people that run no thermostat at all, aluminum radiators and dual fans in turn keeping their car well below the 185 degree mark. I've check my block with a laser temperature reader a few times in the past to esnure that it warms up enough.

Anyhow, sorry for the thread jacking, just wanted to point that out. But based on what everyone here has said I think Burl has enough information to work out any issue(s) he may have. In my honest opinion as long as the car doesn't go over 200 F you should be fine.

Jan

Burl,

Your gauge looks like my gauge did a few weeks ago running down the freeway doing 80 mph with just over 90 degrees outside. My gauge might have been a tad higher.

Thanks to everyone for the great information!

Mike

Oh yeah, my car is only set up that way because I've yet to get a temperature sensor in a convenient temperature range and thread size yet.

My fans are always-on for the sake of temporary convenience only, as that beats the mechanical fan with a thrashed fan clutch that I pulled out.

Just as a point of interest, my original owners manual for a '71 series 1 240Z describes the operation of the water temp gage. It states that the normal

range for the temp. gage is between 170F and 220F indicated. It further states that should the gage read over 240F for more than a minute or two, stop the car, have the engine cooled down, keeping the engine speed at 1,000 to 1,500 rpm, and then check coolant level. 220F on my gage is just a hair over 3/4 needle travel, considered the high end of NORMAL.

I bought my car new in Tucson and drove it in the hottest climates for over 138,000 miles. The temp normally resided over the right leg of the M for most of

that time with the A/C on, 100F+ temps, in the deserts of Arizona, California, and the plains of Florida for 42 years. The engine had never had any issues.

A contributor to this sight, Dr. Joseph Demers, had presented a way to calibrate the temp gage by measuring the correct resistance in the temp sending

unit. I used this to calibrate my temp gage and the reading now perfectly matches temps I am getting using my infrared thermometer. If I can find his

article, I will add it to this discussion.

FWIW,

Dan

Edited June 18, 201311 yr by AZ-240z