Runs hot when cold and other mysteries...

[bnam]

When I left for work (20mi drive one way) at 5:10am yesterday in my 74 Tii, it was about low 60F outside. I was surprised to see the temp guage which normally stay horizontal hover at about a 3rd of the way beyond horizontal and the red mark. When I turned the heat on, the guage dropped, but went back up when I turned heat off.

During my return, temp was in 90s, but the temp gauge stayed horizontal throughout the drive back -- even through the section of crawling traffic.

What would make it run hotter when cold? Or could the reading be higher because I also had my headlights on?

And the other mystery: I had recently installed an Alpine radio -- wired the power thru the existing radio power supply in the harness, an always on +12V from the ignition harness under the steering column cover, and the instrument lighting signal. Everything works well.

Except, as I noticed yesterday -- when I have my headlights on, and I turn on the left turn signal, the radio cuts out for an instant and comes back on. No issue with right turn signal. Both sides work when headlights off. I think the issue is also there if I run with just parking lights.

I suspect it has something to do with the left turn lamp wiring. I had noticed that the lamp blinked even when the lamp was unscrewed from the car body -- perhaps indicating it was grounding thru the parking lamp circuit.

Byas

[jgerry2002]

Headlights on can cause weird readings with the temp gauge if grounds are a little flaky. It can appear "slightly" higher.

The radio install is at fault here. I'd consider moving that to another circuit.

Adding a ground harness to the back of the gauge panel can help things too

[bnam]

The radio install is at fault here.

Gerry, can you explain a bit more on why you think the radio install is at fault?

The circuit it is on (for the power) is the one provided by BMW for the radio, and the constant 12V (for memory retention only) is on one from the ignition.

All grounds had been cleaned out and Radio has it's own ground.

But, I've obviously missed something.

Byas

[jgerry2002]

The factory circuit for the radio tends to be fairly overloaded. Its fine for a vintage 70s radio, but newer units tend to want to draw more amperage. Newer units also seem more sensitive to alternator whine, grounding issues, and other wiring faults.

I'd consider running your own 12v+ for the radio. Separately fused etc.

I have vintage '73 blaupunkt and I dont have any issues with it.

I have an aftermarket / modern radio in the '76 and I ended up wiring it off its own power distribution block / fused. But I did have external amps etc.

[OriginalOwner]

"funny" this topic came up, I was thinking about posting something "just for fun."

Anyway, my '74 tii runs warmer when the air temp is low .... and runs cooler when the air temp is much higher. Not huge, but definitely noticeable.

Case in point, yesterday here in SoCal. I left my house at 7am and drove to Chino, 25 miles. Temp needle just below halfway. Air temp in the high 60's or low 70's.

At 1:30pm in Chino it was at least 100 degrees. I drove 75 miles to Simi Valley, the air temp all the way was at least 100. Engine temp was at 3/8's or so during the freeway-all-the-way cruise. Definitely lower engine temp, with a much higher air temp.

Don't know why, it just is.

Cheers,

Carl

[bnam]

One thought...

The cool denser air could cause it to run richer when cold and then the less dense hotter air in the afternoon causes richer AF ratios. I think leaner mixtures burn hotter.

Or perhaps, the coolant temp valve is slower to open when cold causing it to run hotter?

B

[OriginalOwner]

no idea ..... one theory is as good as another ..... all part of the 2002 mystery.

The upside to this particular mystery: at least my tii is running cool these days. It hasn't always been that way over the past 37+ years. Which could make a fellow quite suspicious and very nervous .....

Cheers,

Carl

[bnam]

Solved the radio/turn signal problem -- rotating the fuses to clean the contacts solved that issue.

Running hot when cold remains. This morning, after a short drive, once again the coolant temp was showing high. So, I stopped and checked. The lower bottom hose was cool while the other hoses to the coolant temp regulator valve were hot. So, it does not seem to be opening up when the coolant in the radiator is very cool. Time to change?

B

[OriginalOwner]

sounds to me like the thermostat is not opening. A cold lower hose (outlet from the radiator) would indicate no coolant flow through the radiator.

Cheers,

Carl