How hot is too hot?

tomnj

tomnj

Old fogie stogie
IMG_20190502_140821.jpg


I'm concerned that my 850 Coupe is running a little hot. Notice the gauge is showing around mid-point. From my experience, it should be just above the white line on the left, sort of the 1/4 position below the "5" in the speedo. That's where it goes initially after warm up. However after some spirited driving, I noticed it climbs a bit to this mid-point. The gauge seems to be working properly. The car was previously filled with just water (PO did that) and it seemed to run cooler that way, now after adding 505/50 coolant, it seems to run hotter. This is on a 75 degree day, it wasn't a hot day.
 
actually pure water is more effective compared with the 50\50 mix with coolant, of course is not good for the motor's health..also these motors do run hotter than many others..i would try to get a second opinion (another gauge , maebe a cheap off ebay one) for the peace of soul..
 
Some random thoughts here.

Straight water will run cooler than antifreeze mix. Interestingly, the "no water" product that is on the market actually runs hotter than a traditional antifreeze mix. The maker of that product (Evans) even admits this, but they like to focus on it's reduced boiling point instead. That is only an issue if you have overheating problems, as boiling won't occur with a properly operating system. They also boast anti-corrosion properties however antifreeze also has similar anti-corrosion properties. It just has a shorter life so you need to change it more frequently. Although at the cost of the waterless product you could change your antifreeze several times. Personally I'd prefer to have the cooler running temps than less frequent changing. But running straight water will result in more corrosion over time, so some sort of protection is best.

The temp sending units and gauges typically are not very accurate or reliable on Fiats (as with many cars). So when you say it seems to be working properly that may be a little misleading. I cannot say much about 850 habits in particular, but mid range of the gauge or higher is normal (at best) for most Fiats. In general I'd say just above the white line on the left sounds too cool? Without the gauge having any temp values (no numbers) it is hard to know. Can you verify the actual operating temp with a infrared gun or auxiliary gauge?

The overall condition of all cooling system components is important for maintaining operating temperature. So check the whole system over. Also, if straight water was run for any length of time you may have an accumulation built up on the internal surfaces. A good flush with a proper agent will help. By the way, most of the flush products on the market today are pretty much useless. You might try one age-old proven agent, oxalic acid. It was the ingredient in all of the better flushes before the EPA decided it should be limited. But you can still buy it as straight oxalic acid powder online (quite inexpensive). Just follow the recommended dilution ratio (also found online).
 
Thanks guys. The car has the early radiator from when it had the 817cc engine, but was upgraded to the 903cc, so not sure if the radiator should be upgraded to the later one too. Are they any different (besides the hose location)?
 
If your car is running that cool after spirited driving, you've nothing to worry about. A later-model radiator isn't going to make any difference.
 
I may be wrong but the Coupe/Sedan radiator did not change capacity or size in the transition from 817 to 903.

My 817 has always run in the area you show with surprisingly little variation.

The big change on 850s was the change to the top hose arrangement that got rid of the air holding top loop versus the horizontal transition from the thermostat to the radiator on the later radiator.

The changes to the 903 waterpump and associated pulleys are the arbiters of the cooling on the 903 (along with keeping the cooling tins and other parts properly maintained and installed).
 
If you are concerned you could always install a mechanical gauge so you have something real to compare the non-numbered gauge to. (don't even have to put it in the cabin just somewhere in the engine compartment would work you are after all just getting something to compare the factory gauge to)
 
An infrared gun would be another way to check the temp. - they don't cost much and come in handy once in a while for other uses.
 
anyway i an undertsand his concerning, my other drive is a '94 cinquecento 900 that has the same motor (with hidraulic tappets an single point injection): it runs hot and is a known head gasket eater..i use the cabin heather to control engine temp (too lazy to mount a manual fan swithc in the cabin..)
 
I always thought that was the normal position. Always has been on mine. Always use a coolant mix for the lubrication of the pump. Don't use a glycol mix if you are in an area where the coolant wont freeze.
 
myredracer said:
An infrared gun would be another way to check the temp. - they don't cost much and come in handy once in a while for other uses.
Click to expand...

I second this. But the gauge just below mid-position is fine. If the gauge is accurate, just above the cold line is too cold and is bad for the engine over the long run. What temp thermostat is in the car?
 
I never did anything with the thermostat. What type should I be running? I just ordered a new one just in case (for $7, that was a no-brainer), didn't install it yet.
 
Here is a video from last Fall, on a cool day (maybe it was 50 degrees). The car was at operating temp, I had just driven it 5 miles before shooting this video, and yet notice the temp gauge, its not even close to mid-point. It's at the 1/4 position. I was running straight water, which I know helps, but the point is, slightly warmer temps shouldn't make it run much hotter, theoretically it should be at the same temp in all climates when at operating temp. My Thermostat might have got plugged or something. Because the PO was running straight water, there is rust in the system. I am trying to clean it all out.

 
The reading of an electric gauge really doesn’t mean anything unless you have calibrated it against a source you can trust. Get an inexpensive laser thermometer and check the temp in the hose from the engine to the rad. As the engine warms up, write down the reading you get next to a description of where the needle is on the gauge. Then you’ll know what temp the coolant is for each needle position.

If you are starting with a cold engine the hose will stay cold until the thermostat opens, at which point it will jump up to about the temp the stat opened, 160 - 180 F, depending on what stat you have.
 
are you sure that the sender is the correct part? my car had a wrong one and the gauge reading was rather erratic..very similar to what you describe..after fitting the correct sender now it works fine
 
A couple of updates...

The timing was off (verified by timing light) and now that it's set properly I think its running a little cooler. Also, I realized that when I made that video last Fall on a 50 degree day, I had the heater on. The heater in these cars no doubt helps in cooling. In fact, I always put on the heater when I suspect a car is over-heating or running hot, as an added measure. I also replaced the thermostat with a new one and even replaced the thermal sensor, though I don't think either had any effect on the cooling. The old sensor was a bit intermittent, often showing no reading so I think it was going bad.

I took the thermal sensor out of my parts car (1971 903cc) and installed it, but the reading is too low. The gauge never goes above the white line on the left now. Just moves around below it. Did they change the sensor or temp gauge through the years (my car is a 1966 and the sensor is from a 1971)? Or maybe the one I put in is just defective.
 
I found a spare radiator that I may use, have some questions:

!. What is involved with replacing just the radiator? Can you take it out without removing the water pump/belts/fan, etc.?
2. Anyone know of a place that re-cores these Fiat radiators that accepts shipping in the USA? I read there was some guy in Dallas TX on another forum, but that post was from about 8 years ago.
3. Anyone recommend using an aftermarket/modern radiator (like a generic one or Honda radiator, etc) to improve cooling?
4. If I choose to run an electric fan, can I still use the stock waterpump? Anyone have info on the process to switch over?
 
There is a shop in Albuquerque that can do any radiator. I had an extra thick one made, don’t remember the cost. It’s an old school radiator shop run by the daughter of the original owner. Don’t know about shipping . J-B Radiator
You can run an electric fan and use the stock water pump. The important thing in the 850 is the ducting so you’d have to make a custom shroud.
I have no personal experience with after market radiators but I will go that route on my next project as the car won’t be stock anyway.
 
You must log in or register to reply here.
Back
Top