I'm only about 5 days into my ownership experience of my first RX-7. It is also my first car which is older than I am, as such, I am finding it hard to tell the difference between a problem and just a fact of life from a bygone era of motoring.

In every car I've owned, the temp gauge needle moves more or less to the center of the gauge once the car warms up, and only ever moves from there if there is a problem.

However, in my RX-7, the gauge barely moves past the 2nd tick, which, if you look at the '85 dashboard, you'll see is barely past the first tick/cold stop. It also usually takes 3 or 4 minutes before the car has warmed up enough for the needle to lift off the cold stop when warming up (I know not to drive on a cold engine).

I'd suppose that the temp gauge might be getting a bad reading, but I do see it moving up and down. When coasting downhill, it can even get below the 2nd tick.

When I was bringing the car home, I got stuck behind an infiniti SUV doing 10-15 mph the whole hill climb, forcing me to stay in first, and the temperature gauge slowly moved up and up and up. I decided I would pull over if it passed the 3rd tick (pretty warm on the gauge). It almost passed the third tick, the centerline of the needle was past the tick, but I couldn't see gauge face between the needle and the tick. The engine was smelling warm (not overheating hit-you-in-the-face smell, just the "burning off crud that was spilled on the engine at some point" smell). Luckily, we crested the hill and started going downhill. In any case, this has given me some degree of confidence that the temp gauge doesn't just read low.

I am wondering if this variance in engine temperature is just what old cars do, or is it an indication my thermostat isn't working right? I would guess it was stuck open, but (1) how would the engine temp get so high if it were, and (2) wouldn't that make it take like 10 minutes to warm up? I've never heard of a thermostat sticking in the middle, and if it were stuck closed, I'd know.

What FB owner can tell me if I've got a problem, or I'm just pampered by modern cars and need to get over myself?

 

I'm not sure on FBs, but i know s4 FCs that the 1/4 mark is warmed up, anything past is overheating, s5's was half way was warmed up, anything more was overheating

 

Thanks for the input, but I'm really looking for someone familiar with FB's. I found another thread with someone asking a similar question, and the answers were all over the place. Some people saying that it's a thermostat stuck open, others saying its likely the gauge. I hope it isn't just a gauge reading low, because that could mean I was really overheating the engine when it was at the 3rd tick mark. That seems inconsistent, though, as I can push the car pretty hard and it doesn't get hot. It was just the prolonged 1st gear hill climb.

It's looking to me like most FB owners find the stock sensor and gauge to be unreliable. I've thought about getting an aftermarket gauge, possibly rigging it up to replace the digital clock in the dashboard between the fan and heater control *****. If I did that, I'd get a gauge that reads in degrees F.

I live directly on a highway, so I don't really have the option of puttering around when I leave home. I have to take 1st and 2nd nearly to redline if I don't want to risk being rear ended, so I expect to always let the engine warm up before I set off.

My understanding is that cold 12a's have terrible compression when they are cold because the housing doesn't expand as much under heat as the rotor does, so the rotor only makes good compression when it's warm. Driving hard before the engine is warm causes excessive wear.

If I'm reading an aftermarket gauge, what temperature do I need to wait for before driving? On a stock gauge I'd wait for it to come past the 1st tickmark, but the stock gauge doesn't read as wide a range of temperatures as an aftermarket gauge would. What should be the target operating temperature, and at what temperature is it safe to start driving?

 

I"m not sure on temps honestly, if you checked the FSM on foxed.ca I bet the answer is there

and you CAN drive it while its cold, just don't hog on it, I drive mine everyday cold (have the past 3 summers) and I don't let it work hard, or go above 3K until its warmed up

 

I live on a california highway with a 45 mph speed limit, on the inside of a blind corner. I can't get out of my driveway in my RX-7 without going above 3k

It happened yesterday that I was stuck behind a car who wouldn't pull over, climbing a hill between 15 and 20 mph, so I was stuck in 2nd gear. Again, the temperature started creeping up, but it hit the 3rd tick before I crested the hill so I pulled over (where the other driver should have) and opened the hood. I saw some smoke coming off the engine but it wasn't coming from any place in particular, and the block was rather oil stained, so I figured it was just crud burning off the block in the high temps. I watched my temp gauge, because if it kept going up at idle, I'd need to turn the car off; but if I turn the car off the water pump stops and it takes longer to cool down.

Luckily the car did cool down to below halfway after about 10 minutes of waiting. I drove off and the temp kept dropping, now that I was moving at a decent pace.

I actually had a conversation with a total stranger who pulled over to check if I was alright, and he just chatted cars with me for a while. That said, I don't look forward to the next time I have to stop because the engine temp is getting hot.

I figure the first step is to drain & replace my coolant and thermostat, though it seems that improper thermostat function would have caused worse issues. Since the heat is happening at low ground speed, high engine speed, it seems like its an airflow, water flow, or heat transfer issue, so its got to be one of the following:

1) My fan clutch isn't engaging when the engine gets hot (makes the most sense to me)

2) Somethings up with my water pump (I'd think this would cause issues when the car is driven fast & hard, but it stays nice and cool)

3) The radiator has scale on the inside making it hard to transfer heat (again, I'd think that this would be a problem that would present it self during hard high-speed driving)

So other than the thermostat, I think it's a non-engaging fan clutch? Does anyone know how to test it? Other than making the car overheat again and turning off the engine and seeing if I can turn the fan by hand...

 

If the fan clutch is bad it will be really easy to spin. Take the fan clutch off and spin it. If there isn't any or very low resistance, it's bad. You can go electric or stay factory.

I you need a factory fan clutch send me a PM and we can discuss.

 

Well, yesterday was a warm day (95F ambient) and the car started getting quite warm while climbing the hill on Highway 9. Unlike previous incidents, I wasn't stuck going 20mph or lower, I was maintaining 30-35 mph. I was being careful to carry as much speed as I could through the corners, and I turned the heater on full blast (not fun on a hot day). I made it to the top of the hill without the temp gauge making it to the third tick, and the temps started dropping once the engine wasn't working so hard. Even though I was confident the engine wasn't getting so hot it would break something, it still smelled bad and was quite nerve racking

Based on what I've read, this doesn't sound like a fan clutch issue, as the fan really isn't doing much above 20 mph. I have turned the fan by hand when the engine is cold and it feels more or less like any fan clutch, some resistance (you cant spin the fan and let go and watch it spin) but not difficult to turn.

I've concluded that the first step needs to be drain the coolant, replace the thermostat ($20) and do a coolant system flush. Based on a guide here on rx7club, I'm planning to drain the radiator, disconnect radiator hoses, drain the block, and install the prestone flush kit in the heater hose.

I am considering maybe taking out the water pump at this point and inspecting it, but that's significantly more work (undoing all the belts) so I probably wont do that unless I'm still having cooling problems after all this is done.

Once I install the new thermostat, I will reconnect the hoses and start flushing the system. When the water starts running clear I'll run the engine a bit to get the water pump to make sure all the coolant passageways are getting flushed, then I'll shut off the engine, drain the water, refill with distilled water and coolant.

Does that sound right? How do I ensure there isn't air trapped in the system? I know that the flushing process will push the air out, but I have to drain the tap water to replace it with distilled water, and I'm pretty sure that will make the system fill with air again. How important is it to use distilled water? Can I get the air out simply by running the engine with the radiator cap off and adding water as air bubbles out, like on a typical car? or is there something special I need to do?

 

Flush the system with the t-stat out. When you drain the coolant, also remove the small bolt that is in the center iron low on the drivers side. This will drain the engine. There is a petcock for the rad.

 

Nothing like coming back to a 2 year old thread!

I did replace the thermostat like I said, and it made a marginal improvement to the temperature control. What I did since then was just... not take the car in any circumstance where it would be climbing a hill behind slow people. I flushed the radiator too, and confirmed that water flows through it. I figured for a long time that the radiator must be partially blocked.

Recently I started getting some strange noises at startup, that could be provoked into being worse with throttle. I know what squealing belts sound like, this was different. It was too low a frequency, like a groan, but not like power steering. I knew new belts were due anyway so I ordered them. When looking under the hood, I thought to myself, "It might be a bearing", and I reached out and tried spinning accessories by hand. With the belts on. Which of course, should result in nothing moving and me feeling stupid. Instead, I found that I could turn my water pump and my air pump by hand with all the belts on and the engine not turning . WOW, both the alternator belt and the air pump belt were loose, and the car had been working for me fine(ish) for 2 years. The alternator belt was just a little loose, and it was easy to tighten. The air pump belt was at maximum tension and very loose, so I think the prior owner installed the wrong size belt.

The new belts came in. Installation was super easy, I didn't have to even jack up the car! I just had to use a pipe wrench on the fan bracket to keep the water pump from turning while i unbolted the fan clutch. With the fan and clutch resting against the radiator, there was plenty of room to slip the belts over. I've deliberately driven slowly up hills in 2nd gear. It's not the dead of summer, but the results are encouraging. The temperature does tick up a bit doing that, but it never gets quite to halfway, and it certainly never gets to near where it was before.

So to wrap up this thread, my thermostat and cooling system were working fine. My fan belt was basically loose spaghetti. I'm amazed the car worked like that for so long.