Running hot/Overheating

[RAC68]

Hi Angus,

The additions you mentioned have been mentioned over time and taken by some. An oil cooler will assist, especially when combined with the use of a lighter viscosity oil then the commonly used 20w50. However, many who have installed an oil cooler have also mounted the unit behind a cut opening in the front lower shroud which means more permanent modification effort then just a mechanical addition … although, I expect it would not be difficult to find a way to mount the cooler radiator that does not require bodywork.

A thermostatic electric fan is also another solution that has been installed by a number of Healey owners. A fan is often mounted on the cross supports in front of the radiator and is quite effective when at idle at a light. However, since the common approach is to install a single large fan, when under way at speed, the fan acts as a block and is often required to keep running to maintain sufficient cooling. An alternative I have used in my TR7 is to mount 2 small AC cooling fans low (out of the direct air grill air stream) and on an upward angle toward the radiator for a more effective arrangement.

Also, such modifications as bonnet louvers, fender vents and fan shroud will also improve air flow and cooling through the engine compartment. One last thought is the creation of a behind grill shroud (not the standard air directing panels but a sealed shroud as used on the competition Healeys that direct all air passing through the grill directly to the radiator core. When at a stop light idle, this shroud will not allow the recirculation of hot radiator exhaust air by providing a sealed radiator intake.

Again, there are many ways to improve the cooling of a Healey but in most cases it would require the correction of a bad engine compartment airflow design.

Just my thoughts,
Ray(64BJ8P1)

 

[RAC68]

Hi All,

After reading "Cooling of the Sunbeam Tiger" referenced by Healey Rick, a few things seemed to mirror what I have been saying. Engine cooling is a function of heat transfer to the cooling system and internal lubrication. However, eliminating heat from the cooling system is a function of its transfer to ambient air via the radiator and requires time and air volume to achieve this transfer. Each stage of this 2-stage process (1. engine heat to coolant, 2. coolant heat to ambient air) takes time for the transfer of heat and having a high coolant flow can provide insufficient time for the stage 1 heat transfer and having a insufficient air flow can cause Stage 2 to be insufficient. Results, an overheating engine.

Our Healey's cooling and air flow configuration are not that dissimilar to the Sunbeam Tiger.

We have a lack of air flow to, through, and out of the engine compartment due to:
1. An inefficient engine fan that moves an insufficient volume of hot air through the radiator and little or no air through the engine compartment.
2. A very porous radiator bulkhead that is far more extensive with opening then that of the Tiger with paths for hot air recirculation.
3. A frame member crossing behind the bottom radiator tank below the fan that directs an air intrusion to further upset any fan efficiency or organized air flow through the radiator and engine compartment.
4. No clear exit of heated air from the engine compartment resulting in the formation of a high pressure block which further slows air movement and cooling efficiency.

As mentioned in my previous post, these issues were address in modifications to competition Healeys, so it was known and appreciated but not exposed or addressed in production cars. The elimination of radiator bulkhead openings with the grill inset pictured, directs entering air directly to the radiator and eliminates the recursion of hot radiator air recirculation. Add a full shroud around the engine fan for improved air movement efficiency and effectiveness, along with fender vents or bonnet louvers to greatly improve the exiting air flow and, I believe, out problems would be greatly rectified or eliminated.

Again, the Tiger presents similar issues, but to a lesser extent. However, their conclusion that the correction is substantially one of air-flow/heat-transfer is the same.

Yes, good cooling is a function of multi-media heat transfers with air flow being critical. Our Healeys were created with a faulty cooling design and many have tried to overwhelm these faults with aggressive fans (electrical and engine) but without correcting the underlying problems. Isn't it time to correct the design?​

Just my thoughts,
Ray(64BJ8P1)

 

[roscoe]

As one who has recently driven the same car ( mine), with an un-louvered bonnet and then experienced it in approximately the same ambient temps with the 100M louver pattern hammered in, I can and will state unequivocally that I notice a difference in foot well temperature. Still warm but not what I was used to.

Since I rarely if ever drive in real stop and go in extreme heat I also have never experienced anything that would make me turn on the heater etc. to lower engine temp. I once pulled the hood release so it would act as a cowl flap on an airplane (or one giant louver) to see if it made a difference and it very slightly lowered coolant temp but definitely made my feet more comfortable at speed. The latter is a move the owners of later big Healeys can't take advantage of unless you want your bonnet to sail over your head.

 

[BOBBYR]

Hi Gang , I saw the article that Ray wrote about Sunbeam Cooling . Now that's a good article ! You mentioned timing of heat transfer . Now you,'re cooking . Some our members go for a ride and come back thinking that their engine temp. is running a little high . They might right away switch out their 180 thermostat for a 160 . Have they cured the problem or only created one ? The engine idle speed of these engines is about 600 rpms . How much water flow is there at 600 rpms when you're in bumper to bumper traffic ? Hot coolant does need a sufficient amount of time in a radiator to cool . Should you try boosting your idle speed to 700 or 750 rpms ? By now, most of you might think that " this guy is crackers " and you're probably right . I just try to keep things simple . By the way , when I went back to a 180 and boosted my idle , it really helped stabilize my cooling system temp . Just a thought . BobbyR

 

[Michael Oritt]

Bobby--

You probably know this but switching from a 180 to a 160 thermostat will not increase the engine's cooling efficiency or, by itself, result in a lower operating temperature in warm weather or conditions where the engine is running at or above 180. On the contrary it only serves to,. at least theoretically, regulate the engine's minimum operating temperature, particularly in cold weather. The only contribution a 160 thermostat might make to a situation where overheating is likely, such as traffic, is that it gives a lower starting point and perhaps might provide more time during which the car can meet the challenge.

In practice, as Bob, myself and others state, a 180 degree thermostat does not seem to keep minimum operating temperatures at that point and for whatever reason if I am driving at sustained highway speeds on a cool day myu temperature may fall to 160-170 notwithstanding the 180 thermostat.

 

[RAC68]

High Michael/Bob,

As I see it, an engine will not achieve minimum rated thermostat operating temperature when sufficient cooling heat transfer is taking place or a thermostat fault is present. This condition can only be caused when engine heat is being transferred to its cooling systems (coolant or lubricants) to lower and maintain operating temperature below the thermostat setting and has been experienced when the coolant is allowed to freely pass coolant through ByPass channels without thermostat restriction. However, since radiator flow-through is blocked by a closed thermostat, it appears that the ambient outside temperature would need to be sufficiently low or a path through the radiator is present, for coolant heat exchange, to eliminate sufficient amounts of operating heat build-up to maintain this condition. However, this condition could be supported if an oil cooler is incorporated into the engine cooling system without a properly functioning oil-cooler thermostat and operating heat is being reduced via lubricant heat reduction transfer through its independent radiator (heat exchanger).

I appreciate that you have indicated testing the thermostat and finding it performing properly. However, we all know the purpose of the thermostat and if it performs properly, it is being bypassed in some way to allow a coolant heat exchange to take place. One last thought is if your Heater connection (valve and adjuster) are open and allowing the bypassing coolant to flow to the radiator for a cooling heat exchange. This could possibly bypass the closed thermostat and maintain sufficient engine cooling on a cool day to never achieve the thermostat trigger temperature.

Just my thoughts,
Ray(64BJ8P1)

 

[Michael Oritt]

In any case it appears that our cars are air conditioned: "Hot in the summer and cold in the winter".

 

[Keoke]

in any case it appears that our cars are air conditioned: "hot in the summer and cold in the winter".

yep: Lol

 

[BOBBYR]

Hi Gang , I promise this is the last time I'll beat this dead horse but I must admit it's been fun and enlightening . My healey with a 160 thermostat , I think , is just continuously open which never gives the coolant in the radiator time to transfer the heat to air . I was surprised no one mentioned the idle speed . A few years back , U.P.S. ordered a bunch of new trucks and because my fleet was getting so high in miles , I ended up getting 10 new trucks that year . They were Navistar computerized diesel powered . These motors during development had a tendency to overheat at idle . The cure for Navistar was to program their ECMs to boost the idle rpms up by 100 rpms at a set lower tempature . The engineers said better coolant circulation . During that time when I'd be out driving my Healey , I always thought my engine temp. was too high for my liking . That's when I changed idle rpm up and the thermostat . It just seems to have stabilized my cooling system regardless of traffic conditions . I promise I'll never bring this up again and thank you for putting up with me . Thanks, BobbyR

 

[Healey Nut]

I will say a humungeous “AMEN” to that and maybe just maybe we could do the same for the never ending oil debate ....that would be an “HALLELUJAH AMEN” if that happened
not going to hold my breath about that tho :smile-new:

 

[steveg]

Hi Gang , I promise this is the last time I'll beat this dead horse but I must admit it's been fun and enlightening . My healey with a 160 thermostat , I think , is just continuously open which never gives the coolant in the radiator time to transfer the heat to air . I was surprised no one mentioned the idle speed . A few years back , U.P.S. ordered a bunch of new trucks and because my fleet was getting so high in miles , I ended up getting 10 new trucks that year . They were Navistar computerized diesel powered . These motors during development had a tendency to overheat at idle . The cure for Navistar was to program their ECMs to boost the idle rpms up by 100 rpms at a set lower tempature . The engineers said better coolant circulation . During that time when I'd be out driving my Healey , I always thought my engine temp. was too high for my liking . That's when I changed idle rpm up and the thermostat . It just seems to have stabilized my cooling system regardless of traffic conditions . I promise I'll never bring this up again and thank you for putting up with me . Thanks, BobbyR

One can raise the idle in hot situations or in the mountains by pulling the choke out enough to engage the fast idle, but not enough to lower the jets.

Still waiting for an authoritative explanation for why on cool days we never reach the thermostat opening temperature. Installing a jumper tube cutting off the heater input and output hoses would be a way of testing for Ray's theory that the heater might be doing enough cooling to keep the temp down.

I enjoy those of us who "think out loud" on some of these hardy perennial topics. I'm good with bringing it up again as long as there's new material, like Bobby's post above. Not as a substitute for searching the archives, however.

 

[Michael Oritt]

I must admit it has been a while since I have verified the temperatures at which my thermostat begins to open,etc. using a thermometer in a pan of water on the stovetop.

 

[RAC68]

Hi Bobby,

First, please participate as YOU feel appropriate and those who have a lack of interest have the option to pass by the topic.

Since engine fan and water pump speed is governed by the engine's RPM, it stands to reason that raising the idle will increase the speed of hot coolant passing through the radiator as well as the volume of air passing through for transferring heat. However, this may not be as beneficial as you would think as a high percentage of a Healey's cooling air, at idle, is recirculated (previously passed through the radiator and exited from the engine compartment via the large openings in the radiator bulkhead and pulled back through), resulting in a pre-heated cooling air temperature and a reduced coolant/air temperature differential.

So, with the many modifications tried and incorporated into each Healeys by their owners, if it works, be pleased and enjoy your Healey.

Ray(64BJ8P1)

 

[Michael Oritt]

Ray said: "First please participate as YOU feel appropriate and those who have a lack of interest have the option to pass by the topic" and to that I say, "Hear hear."

We have apparently not gotten to the bottom of the many-faceted issue of why Healeys are so prone to overheating--and now underheating. Let's not forget that each of us was at one time new to Healey ownership and we are all simply at different places on the curve of learning about the many things that make our cars so idiosyncratic. Why should we require anyone to have only NEW questions about cars that are 55-65 years old? And what better do we have to share our knowledge (and bandwidth) with those new to Healey ownership.

So, to Bobby and whoever else might be lurking out there I say "bring on the questions"--we might even know the answer to some of them!

 

[steveg]

Michael - I was trying to encourage folks to use the search function, as there's a world of info there. Now if it were only a little easier to use...

 

[Michael Oritt]

Steve--

My remark was not addressed to your post. :fat:

 

[Bob_Spidell]

I know the nominal idle speed for a Healey Six is 600RPM, but I've never been comfortable that slow a speed (the modern, FI cars I've owned all idled at about 750RPM, but the new Mustang seems to idle a little less than that--maybe with two types of fuel injection you can do that). If nothing else, a stock generator seems to require about 700RPM to extinguish the 'ignition' light, which, when lit, indicates the car is running off the battery, something you don't want to do for too long. Also, sometimes, on hot days and/or in traffic, the idle will drop a little, and 600 doesn't give much of a margin. But, I can't think of any thermodynamics-type explanation for increasing the idle to cool the engine; you are, of course increasing the work, hence the heat generated.

The only thing that I can think of that would cause an engine to run below its thermostat's setpoint is a stuck-open thermostat. But, I think we've established that's not the cause for the phenomenon we're experiencing. I just think "Why don't you do that when I'm stuck in traffic on a 90degF day!"

Funny, but I've never had a problem with threads I'm not particularly interested in. Just hit the 'go to last' icon and then the back button; a small price to pay for all the good info on this, or any, forum.

 

[Editor_Reid]

It may seem counterintuitive to rev your engine - or increase the idle speed - when it's running hot, but the practice of revving it to reduce operating temp goes way back.

Thanks also for the reminder that the choke knob, if the choke cable is properly adjusted, is a good and easy way to increase idle speed to achieve the same thing.

 

[Keoke]

So, to Bobby and whoever else might be lurking out there I say "bring on the questions"--we might even know the answer to some of them!

​

 

[andrea]

On the complete rebuild of my 100/6 I have a lot of attention to cool problems
the radiator was rebuild and TEXAS fan and a thermostatic controlled electric pushing fan
I have added also one Oil Radiator -with thermostatic valves control-
https://photos.app.goo.gl/jT7Ci3P69tobe8sB9
I remember the false assertion that my 911S was AIR COOLED it have 13 Liter of OIL not the sump- two oil pumps - a big underwing oil radiator- it was OIL cooled (13 liter is nearest the AH water supply of our cooling system) the forced air helps only
Summer in Italy can be so hot as in TEXAS 40° C degree can be normal -and there are a lot of hard climbing mountains, windy roads
Traffic can be very slowly or stopped for car accidents or congestions
In 5 year of long trips on AH i find all this situations and no problems of overheating occured
I know AH engine bay haven't sufficient air flow capacity and this must be considered during the restorations