peace of mind regarding coolant temps

I have a lot of people asking me about the temps of their Ferrari and that it runs hot during summer months (the 3/4 mark or beyond this mark on the gauge is the typical point of concern). I have installed big aluminum radiators on a number of cars, and while they definitely help a ton when the car is moving they cannot avoid a bit of a spike when a person is stuck in the dead of traffic on a 93 degree day with extremely high humidity, the car runs a bit hot, it just does......or does it?

First of all, I believe Ferrari were bound by the technology of the day and what coolant and oil could handle at the time. Additionally, everyone during the pre 90s era seemed to be certain that an engine needed to run between 165-185 degrees. With oil and coolant being what it was I believe there was some truth to that to a certain extent.

As oil and coolant technology were more understood we starting seeing Ferrari -starting with the 360 whilst the 348 and 355 showed a bit higher 'higher end' of the temp gauge than just 250 of prior gen cars- raise the center mark on the coolant gauge to 210 degrees as opposed to the 308/328 era 195 degrees.! The 210 mark being dead in the center on a 360 all of a sudden makes a 308 running at the 3/4 mark (which is about 225 degrees) sound much better now doesn't it? Read on:

If you're using let's say a 15w/50 mobil 1 oil, that oil basically doesn't even begin to do its job as a properly thick performance racing until until it is 100c (212F). If you have that oil running well below that temp all the time then there is no point filling your engine with that oil, there's just not. Thankfully, our engines usually run pretty darn and they rev pretty high so it's a good idea most of the time to use that 50w fill, but rest assured if you're running a steady 225-230 degrees you're going to be ok! Your engine actually should run best when it's above 210 degrees, so try and keep it there if you can.


It turns out coolant has some fantastic properties that are ideal for use in engines. With its excellent characteristics engine designers have decided that engines should operate at approximately 210-215°F. This has to do with operating the engine at a high enough temperature to boil water out of the oil after the engine is cold started. If you have dew on the grass, it is certain that you have water in your oil, as the crankcase is open to atmospheric pressure! You can either remove the water by draining it out the bottom of the oil pan ( oil floats on water) or run the engine long enough and hot enough to boil the water out of the lubrication system. Years ago, coolants weren't as sophisticated and engines were run at 165-185F, but the oil was changed far more often which is some of the older generation think engines should run at 165-180F. Have you ever noticed that Ford doesn't put temperature marks on their gauges? They just mark C for cold and H for hot and write “normal” through the center, and often times other manufacturer don't even have that. If you hook up a scan tool to a GM, you will often find that the gauge reads much lower than the coolant temp sensor. That is because they know most drivers don’t understand how hot an engine should run.

Many enthusiasts believe that the colder their engine runs the better. If they are not running the engine hot enough to boil the water out of the oil the oil becomes contaminated What good does it do to use the most expensive synthetic oil and then run the engine so cold that it is contaminated by water vapor??!! Another point, piston manufacturers piston clearance recommendations assume you will be running the fully warmed engine at 200°+F (this of course is dependent on the compound of aluminum being used as well). Run the engine too cold, and you could see some scuffed pistons because the cylinders had not expanded enough.

If you keep the engine hot (not the intake air), you will be using more of the heat energy in the gasoline to make power instead of just heating up your block. I suggest to carb era and 80s era Ferrari's be tuned so it runs it's very best at 200-215°F or so, they run incredibly well when you do! Chances are your engine is already tuned well enough and will run just fine at those temps and above, so take a breath, relax.

Modern F1 engines, NASCAR engines, rally engines, truck engines, just about anything you can think of these days was designed to make best power in a window of 210-235 degrees, and often times runs on a heck of a lot thinner oil than we run (they also run tighter clearances), so rest assured that if you're nearing the 3/4 mark in an older Ferrari, don't call an ambulance (flat bed), just make sure your expansion tank cap has a 1.1 bar cap unit and good coolant hoses and a solid radiator and you'll be fine. Modern oil and coolant and the industry in generals better understanding of how an engine likes to run makes running your Ferrari no problem at all in these situations.

In conclusion, your 195 degree center mark was just another product of that which was typically misunderstood of the day, much the same as with valve porting and head flow, combustion chamber design, piston to deck clearance, suspension geometry (I could go on) which are also hardly optimal in a lot of these engines as well. So rest assured, hitting that 230 mark or nearing that mark in gridlock traffic isn't going to harm anything. Drive on
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Agree with you on not worrying about hitting 3/4 on the gage. I would argue that with manufacturing advance they can cast the water jackets to provide more consistant temp control. This would make me a bit more wary about going much higher in the temp range on the older engines.

 

Agree. And good point.

I think with at least carb car guys, many mistake cooler running temps for performance when most of the time it's fuel that temps that matters more. Fuel should be cooler but it's darn hard to stay cool in the very hot carb fuel bowls hence why carb engines do like slightly cooler running, but it's not because the engine temp, it's those pesky carbs making the car have several personalities depending on the weather.

 

My 77 carb ran 170* all of the time , hot or cold AC on or off. Always ran great and the fans never turned on.

 

Yep. Most of the early pre cat cars are like that, especially when jetted a bit for power. It's the QVs that really had issues.

 

At a technical level I don't know enough to agree or disagree although it does makes sense, at least on modern engines. At a practical level I've never seen my Euro QV past the halfway mark (90C). If it got to 3/4 that would tell me something is wrong since it's never done it before. Older cars do tend to bounce around on the gauge compared to newer cars. I can visibly watch the needle move when the thermostat opens, it climbs back, then again when the fans kick on. I don't think I've ever seen the temp gauge on a modern car (made in the last decade) move from dead center, regardless of AC, idling, fans on/off, etc.

How does oil temp factor into this? It seems to me that might be a better indicator for some things. In the manual I believe oil temp is used as a the reference point when its safe to open the throttle up rather than water temp for warmup purposes.

 

The 3/4 doesn't bother me that much.

When mine pegs the far right in Atlanta on I-85 South in traffic every single time - that bothers me. Nothing I have done can stop it.

Interestingly, the ONLY times the water NEVER gets "hot" is on the track. I have spent 20 minutes bouncing it off the redline in August here in Alabama and the needle will never even hint to a right swing past straight down. The oil will peg, but not the water.

Never understood that.

 

Keep in mind that high water temps REQUIRE high system pressure. not sure about F1 but NASCAR engines run 50-60 psi to keep from boiling. It's not just about water temp at gauge, areas around the chamber and exhaust port can have localized hot spots where steam pockets can occur. This causes a barrier not allowing the water to transfer heat.

 

Oil temps need to run a bit warmer so to burn off any excess fuel and condensation, especially if you're running a 50w oil. Getting your oil north of 210 is when that stuff really starts to burn off so my recommendation is to get the engine to that temp every time it's driven. The manual indicates not to go above 6k before reaching 160 oil temp which remains standard in even modern cars which usually feature a rev limiter until oil temps are safe.

 

Thanks John for taking the time to post this great info. Question arises: go by oil temp or water temp gauge which is always at 1/4 while moving and never above 1/2 while sitting?

 

Water temp is generally the one to monitor most as it's system is one that tends to have the most issues ie. hoses, pump, leaks etc. Sounds like your temps are fantastic though!

 

And yesterday, here in NNJ, The weathermen were saying it was high seventies & 20% humidity. I think more 85 & 40% humidity. But the wife was in the car, so the air was on. 60 degrees coming out the vent. But with normal secondary road traffic, red lights, etc I was seeing 3/4 on the oil/water gauges and even creeping above that. I get nervous. Time to shut off the air (which makes a big difference) Once I get moving (45mph+) it drops to 1/2 guage. That makes me smile.

No such issues with the 355.
And my daily driver? I've NEVER seen it past 1/2 guage. And it warms up in winter way faster then the 308.
I wonder : I was chatting with a mechanic who was telling me 12 cylinders are very hot running. Maybe the difference from the 308 8 cylinder to today's 4-banger is a function of block mass.

BTW: running Castrol 20w-50 dino in the 308.

 

In high nineties, A/C on, heavy traffic, high humidity, very sunny days I've never seen either gauge go above mid dial.

How much can we trust these gauges?

 

On most new cars the temp gauge will be dead center on normal as long as it is in the normal range. The sending unit reports to the computer. The computer sends signal to gauge. It's programed to not fluctuate unless out of range to keep customers from worrying over small movements

 

The temperature gauge is not due to any misunderstanding at all, it's actually based on the physics of what happens to water under pressure. The system was designed with a 0.9Bar cap, that translates to 115*C or 239*F maximum temp. Now why is it that low? ... look to the thermostat, it's a multistage unit that acts as a control valve to the radiator circuit. it has three points, 20, 75 & 96 C or 68, 167 & 204.8 F each point has a corresponding lift or valve open point.

The reason for such control is due to the large size of the cooling system, if the thermostat dumped open at once there would be a large swing in temps for the engine shocking it and causing running problems. by controlling the flow with a variable valve the system can maintain a finer control on the temps and keep the system within optimum operating temps. running higher temps will damage the thermostat, given it's very important job and cost I'd be concerned about it.

Now occasional temps above 195 are not a problem, sustained temps above 210 can be though, that's the point at which the thermostat no longer cycles, and given the massive size of the cooling system for that volume of water to be that hot for long periods of time would indicate that something is not right.

The 360 also runs the same setup, operating temps are 77~81C 170~177F open point on stat, with a maximum allowed of 120C or 248F, given the complexity of the system including the inclusion of engine management to the temps of the cooling system sustained temps that are above 210 will cause problems.

the operating point of the 308,328,348,355 & 360 is around 195F the entire system is setup to try and hold or maintain the temps in that area. will it go higher at times, yes, but it should return to 180~200F long term temps beyond that indicate a problem somewhere.

The oil system is not passive like found in many other vehicles, with the exception of the 308/328 it's a drysump setup with it's own coolers/fans etc..

 

FWIW, my needle goes to the 195 mark and the fans come on. Doesn't go any higher under any circumstances. However, I cannot get any heat in the cabin. I've bled and bled and bled. Cannot chase a leak down. Nothing on the ground, ever. Always get a little foam when bleeding. So I must have a leak. I dunno... Any suggestions?
I just completed a belt service so most of the coolant, or maybe half, was dumped. Just filled with water. Plan on trying a flush. Bought a bottle of Prestone flush. Don't expect it to have much effect.
Is it possibly the thermostat?

 

While the engine was designed to run at around 195, that just isn't the case with some engines during these hotter months, especially with QV engines. Many have changed to a 1.1 bar cap and I can't blame them for doing so as with modern oil and coolant technology everything should be fine. A properly operating thermostat in one of these doesn't fix the fact that some run hot, some just do but if everything is good in the respective systems then there is no reason to freak out. I also can't blame some for reshaping the intake port or using a different shaped set of valves in a 2v head, they just weren't great to begin with but no one knew any better at the time they were made. Stuff changes. No sense overcomplicating.

 

Thanks guys. 🙏

 

Have you flushed your radiator to make sure it's not full of rubber 'crumblies" from aging hoses?

Mine only reach the "third mark" if indeed I have lost a fan, or stopped in traffic or of course both!

That said I feel the engine "likes" a higher temp and don't sorry about 210 at all.
We'll see if a new pump with "like new" flow makes my #20405 hit the marks any differently.

I probably should take my own advice and get the radiator cleaned!!

 

It sounds like you diverter valves have come off the linkage from the console or are stuck internally??

 

No. I checked them. I removed the fiberglass covering under the hood. Can't find any leaks. The diverter valves are moving freely.
Last night I used a Lisle spill-free funnel to run water through bleeding at the radiator. Got a little heat but nothing serious. Gonna run all the coolant out and try the rad flush. Maybe it'll free up something stuck. I hope.

 

Coolant temp control has been my nemesis until I designed my "SuperCool Circuit" which allows me to turn on the radiator fan (I only have one fan, but it has greater CFM than the OEM pair) and a fan located at the oil cooler in the engine bay. Both fans are started by the temp switch in the radiator and /or by the user-operated switch in the interior.

No overheating yet...even on hot, humid days in GA (where delta heat capacity is a minimum) due to very high humidity.

 

I have a David Helms hose kit, oil cooler fan, a big fat aluminum radiator, 180 degree fan switch, a new STOCK thermostat and one of Verrell's bleed screws on the t-stat. Bled and bled and double bled both ends regularly. I have about a 70:30 water coolant mix (more water for more thermal absorbtion) Water wetter and a 1.1 bar cap.

 

Gentlemen,
which make/model did you get for your oil cooler fan? I've been wanting to install one for a while.
Thanks.

 

I don't understand why you had these issues on a 328 Rob. My car is entirely standard & I've spanked it up & down mountains in Europe & sat in traffic jams in 90+ degree heat & it really doesn't move off the 2nd mark unless sat stationary when it climbs to 195, the fans cut in & it falls back to normal (fans off, rinse & repeat).