peace of mind regarding coolant temps

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.

 

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.

 

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.

 

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?

 

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?

 

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).