Some observations/results to slowly diagnose why my Healey overheats at idle

[shortsguy1]

I have access to my Healey 3000 BJ8 for the next few days but am unable to do any major projects on the car. So instead, I am just trying to diagnose why my car will get too hot quite quickly when stopped and at idle. Today, my goal was to understand the coolant and oil temperatures of the car at idle after a drive. I put together a few thermocouples and read their values to learn a few things about my car. I have no idea if this is of any value to anyone else, but on the off chance....

1) My oil cooler does nothing to address overheating when parked at idle. My oil cooler is mounted between the frame rails, slightly below the radiator. At idle, the inlet and exit temps of the cooler were identical, suggesting that the engine fan causes no air flow through the oil cooler. I have the stainless flex fan currently installed.

2) The temperature gauge in my car is shockingly accurate up to 225 F. Above 225F, it appears to stop moving, even though the scale goes to 230 F. (I know these are high temps and should be avoided, but that is the whole problem with my car. You cannot avoid them if you drive in summer.)

3) Using an IR thermometer reading the side of the top tank gives the correct temperature of the coolant exiting the engine. I compared this with a thermocouple inside the radiator (I had the rad cap off for some of this) and a thermocouple under the upper rad hose at the radiator and all three measurements were identical. So for others trying to figure out if their Smiths gauge is accurate, you can compare with an IR thermometer shined at the side of the top tank with good results.

4) The temperature drop through my radiator at idle is 5-6 degrees F. I don't yet know what to make of this result, but it was a little smaller than I expected.

5) The oil temps are consistently less than the coolant temps. I would stop an experiment when the car reached 225 F, and the oil temperature was always 190-195F at this point. So I guess my point is that even though the car's coolant is extremely hot, the oil is probably still doing fine.

6) Closing off the coolant bypass had ZERO observable effect on the rate at which my car overheats at idle, after a drive. I did the same short loop today with the bypass open and with the bypass closed. It is very hot here today, so the car was at 195 F when I pulled to a stop. Within 5 minutes, the car had always reached 225F, regardless of the status of the bypass. So it is strange to say, but closing off the bypass doesn't make much (or perhaps any) difference in my car. So I won't be rushing off to purchase one of those rather expensive bellows thermostats with the bypass ring.

Tomorrow, I plan to measure air velocities through the radiator and measure an array of temperatures in front of the radiator. My eventual goal is to figure out if hot air is recirculating through the radiator. I am trying to be systematic and solve this little puzzle one change at a time. Thanks for reading.

 

[bluegrass john]

I find your work so far very interesting; I am curious what your findings are concerning air velocities through the radiator and maybe you can find a way to improve air flowing through the radiator to help the healey overheating dilemma.

Thanks for sharing............I have enjoyed following your work!!

John

 

[Bob_Spidell]

I drive my BJ8 all through the Southwest and its deserts, Death Valley at 115degF and, as you noted California gets plenty hot at times. Sitting at idle for a few minutes on a hot day my gauge will register up to boiling, but not often. Overheating, esp. at idle/slow speeds is a known issue with Big Healeys. The most important factors that I've found are:

- block must be clean, with no sediment or rust residue
- uprated, 4-row radiator core helps as much or more than anything ('Excel' brand is often recommended)
- uprated fan; either 'Texas Cooler' type or similar. I once had a Hayden 7-bladed flex fan installed; at idle it would blow dust and leaves out from under the car, but flattened-out at speed and you couldn't hear it. I took it out and installed an original Texas Cooler. The flex fan worked better, but the noise was too much for me. I also have a partial shroud I got from BCS a long time ago with the flex fan, and it probably helps a little but would work better if it enclosed more of the fan. I do have a Robertshaw thermostat modified with the sleeve to close the bypass; I didn't notice a significant difference when I installed it.
- timing, carb tune, etc. must be spot on. Retarded timing, in particular, will cause overheating.

The overheating is attributed to lack of flow through the engine compartment. Side vents would likely help.

 

[bdcvg]

Sounds like a plugged radiator to Me. With the hood open it should take quite awhile to overheat at idle. If there is any air going through the radiator at all , temp drop with be more than 6 deg.

 

[Brinkerhoff]

Hold a bright shop light behind the radiator and see if its visible from the other side.

 

[shortsguy1]

Hi All. Thanks for the thoughts. I should have provided more background. The engine was rebuilt one year ago and the block was boiled (whatever that means). The mechanic said that very thick deposits had to be chipped from the block. So it may not be perfect, but the block openings are as good as they will ever be for this particular engine.

Also, the radiator got a new updated core attached to the old radiator tanks (also 1 year ago). I don't recall the details of the core, but it was an improvement over the original core. I haven't driven the car enough to get too many bugs stuck in it yet. Again, it may not be the absolute best radiator available, but it is in quite decent shape.

So I feel that water flow shouldn't be too restricted. At idle, obviously the coolant flow rate and the air flow rate will be minimums. The small drop in coolant temperature (5-6F) suggests that the coolant flow is adequate. At a too low coolant flow rate, you would expect a large drop in temperature of the fluid because its residence time in the radiator would be long. So as many have already learned with these cars, the issue is probably low air flow rate through the radiator or recirculation of hot air around the radiator from the engine side back to the intake side.

My metal flex fan really moves some air (and really sounds annoying). So I am leaning towards recirculation being the problem. But I want to be sure about each conclusion before I get ahead of myself. Eventually, I would like to swap in the red plastic fan from Denis Welch, because I believe it will be quieter then the current set up. But I would only do that if I can be sure the air flow is similar between the two aftermarket options.

 

[Keoke]

IF You have not upgraded to all the items "Bob" pointed out I suggest you do.

I did them years go and heating at idle or in traffic is is under control

 

[RAC68]

Hi Shortsguy1,

First, I am very impressed with the work and analysis you have already performed and can only suggest that you proceed and look at the air flow temperature passing through your radiator. One of the major issues relating to the engine's operating temperature at or close to idle (i.e. traffic light or heavy traffic) is the fact that the radiator bulkhead is extremely porous. This condition is further exacerbated by the lack of directional air flow control due to no fan shroud. The issue is that, unless you have bonnet louvers or fender vents, the air drawn through the radiator finds an easier escape forward, with a large portion of this pre-heated air easily mixing with a minimum of new air and, again, sucked through the radiator. As time passes this process becomes iterative and the air temperature being depended upon to cool the coolant continues to increase in temperature.

Due to its design, it is impractical to seal the radiator bulkhead but the installation of a fan shroud will improve fan efficiency and rearward directional flow. A less invasive (visual) approach to a fully encircling shroud is to install 4" vertical panels mounted to both sides of the radiator to help rearward flow and reduce the ease of forward escape. Either approach (full shroud or vertical panels) will help keep already-heated air from being reused in favor of cooler ambient air.



To validate this is an appropriate issue to address for you, I would check the air temperature just in front of your radiator and observe its increase entering the radiator over a reasonable idle period.

Hope this helps,
Ray(64BJ8P1)

 

[shortsguy1]

Ray and others-
Thanks for taking the time to reply. I had intended to use today to measure a grid of flowrates in front of the radiator, but the car heats up so fast that I didn't get very far with that. But then I noticed something interesting... at the front grille, towards the right edge (as you look at the car), hot air was actually coming out from the grille (and probably heading back into the radiator). So I decided to tackle that first.

Using corrugated plastic scraps and lots of tape, I clogged the space between the radiator and the left engine compartment wall. After doing so, the flow through the grille is all in the direction it should be. The car still over heats, but it was taking about 8-9 minutes instead of 5 minutes. So if I can make this solution more permanent and less hideous to look at (pics tomorrow), it is a step in the right direction. I focused on the side with obvious recirculation issues out at the grille, but perhaps doing a similar treatment on both sides will be even better.

I then removed all of that temporary material and built a temporary fan shroud. This followed the straight edge of the radiator on the passenger side, but needed to bow out a little to clear the fan on the drivers side (left side). It is quite similar to what Ray shows above, but a lot more temporary and ugly. With this set up, the front grille of the car is basically stagnant to air flow at the extreme edges. No air was blowing out (so an improvement), but no air was being pulled in (again, at the left and right edges). Using thermocouples, I was able to verify that hot air was recirculating on both sides of the radiator with this set up. So even though my shroud extended from the radiator to a couple of inches past the fan, the pressure built up still allowed hot air to recirculate. So right now, I am not planning to pursue a fan shroud.

So main takeaway is that for my car, clogging the space in the plane of the radiator but to the side of the radiator is a better solution than a fan shroud. But the car still overheats rather quickly. Keep in mind, we live in California where the weather is hot and the traffic is heavy.

I will try to put a picture or two up tomorrow and I made a nice graph of radiator temps vs. time for some of these solutions. Thanks for all the help.

 

[shortsguy1]

This is a pic of the clog of material to the side of the radiator. Lovely isn't it?




This is my temporary fan shroud. This solution didn't work as well as the first solution.




And during both of those tests, I tried to clog any gap on top of the radiator. Nothing is more masculine that taping a pink tea-towel to the radiator of an old british car.

 

[RAC68]

Hi Shortsguy1,

As Steve has mentioned, sealing the radiator bulkhead is close to impossible. Also, a while back I installed a cold air duct fan to aid in cooling the driver foot well was less then hopped due to its draw of hot escaping radiator air. Since the area surrounding the radiator is quite open as is the space between the bottom tank an the cross frame member, instead of trying to seal the area, I had considered constructing a duct/box from the radiator to the grill that would, I thought, entry of hot escaping air from being recirculated. This duct/box would require the elimination of 2 original air directors mounted in front of the radiator and could be mounted and soft-sealed to the radiator side mounts and top and bottom tank surfaces. Since the air would be drawn from the grill (or as close as reasonable), any hot air escaping past the grill would have a greater possibility of cooling with a lower probability of being recirculated. Keep in mind that this is only an idea and has not been tried by me, although I expect someone may have.

However, I am concerned that you temperature rise is quite dramatic and quick which leads me to think there is another condition, other then hot air recirculation, that is exacerbating condition. You indicated that having the bypass open or closed made no difference. This is curious as I was under the impression that, with it open, almost 25% of your coolant would be diverted from passing through the radiator.

That's all I have at 3 AM,
Ray(64BJ8P1)

 

[mgtf328]

I have a BJ8 with the same problem. A friend pointed out that I have two radiator deflectors missing from my rad. The photo shows the pieces. They fit in front of and to each side of the rad and are designed to stop air circulating around to the back of the rad. They are available from https://www.ahead4healeys.co.uk/INNER-BODY-PANEL--IP--ct179.aspx in the UK. They are designed to produce the same effect as the picture shown by Jedi Knight above but they fit in front of and not behind the rad.
My friends BJ7 has a hole punched in the front cross member (above the grille), where the X brace (in front of the rad), meets the cross member. The top of the deflector is bolted to this hole. The bottom end of the deflector fixes to one of the lower grille mount bolts. There is a strut which ties the two back, bottom ends of the deflectors together. The other recommendation I've had is to blank off the space behind and at the bottom of the rad back as far as the sump.
I don't seem to have these holes on my cross member so to drill them is a rad out job. I'd like to know whether these deflectors work. Did you have them fitted to your car when you took your measurements. They seem to fulfil the object of preventing the circulation you went to the trouble of trying to stop. I don't want to go to the trouble of fitting them if they don't work!
I have experienced this problem with a 1954 MGTF I had. I took the rad out and got a local shop to re-core it. I visited the same shop yesterday and he recommended I do the same thing to the Healey. He fits a new 3 core element but instead of all 3 cores being in line with the direction of air flow one core is staggered so that only two of the 3 are in line. He says this gives a 30% increase in cooling capacity. It worked for my MG. It's about the same price as fitting a "push" electric fan in front of the rad. He says he's done it before and it works. I've noticed a few people have fitted electric fans in front of the rad but the size of the fan makes me wonder whether it makes things worse when the car is moving as it blanks off a lot of rad area.

AJ
ps. I have a Dennis Welsh red 6? blade fan fitted. I haven't noticed that it's noisy but I've not experienced the car with a stock fan to compare. My temperature reaches about 210F on a hot 85F day. But it rarely gets much hotter here.

 

[RAC68]

Hi AJ,

The deflectors were standard on big Healeys and most helpful when the Healey is at moderate or higher speeds but do very little or nothing at idle or progressing slowly in traffic. Recirculation is caused when the air drawn through the radiator has an easier passage through large openings (i.e. Steering box opening, etc.) and a large portion of the escaping hot air is redrawn by the fan through the radiator.

Although I am not a proponent of forward-installed electric fans and see them as a block in front of the radiator, I must admit if positioned far enough forward, a large enough fan could pull in sufficient outside air with enough force to provide some resistance to hot air escaping forward (as if simulating the air stream of a moderately forward moving Healey). This will not be the case if the a standard sized electric fan is mounted on the face, or even a little forward of the radiator and I think would only work if mounted close to the grill.

I would also encourage the installation of a 4-row replacement core as I have found it very advantageous. Additionally, I have found, as apposed to Shortsguy1 posted findings, that a sleeved thermostat is beneficial in stopping almost 25% of the coolant from bypassing the radiator.

It may seem odd but when my Healey was new, I had no issues with overheating .... that I can remember. The 4-bladed yellow fan seemed marginally sufficient to handle Jersey Shore traffic jams and desert summer temperatures. As I look back, the recirculation issues began around the time I installed the more aggressive Texas Cooler that drew larger volumes of air through the radiator. Could it be that the greater volume of air passing into the engine compartment has overburdened the original escape paths and resulted in the forward escaping recirculation problems?

Just some thoughts,
ray(64BJ8P1)

 

[shortsguy1]

Ray-
One experiment that I wish I could run this week, but didn't bring the correct tool, is to measure the flow rate of the coolant directly at idle. There is a chance that my water pump is not moving sufficient fluid. This isn't supported by my small Delta T values for the coolant through the radiator, but it would have been nice to measure it directly. Maybe I will get brave and give it a try.

AJ-
My car does have those radiator side deflectors installed in front of the radiator. They do help... sort of. Here is my evidence. Before doing any of my blockages or clogging of the air recirc problem, I was able to measure hot air coming out from the front grille of the car. It was only at the very right most extreme (when looking at the car). The direction of flow changed as you moved from one side of that deflector to the other. So basically, the deflector was doing its job and keeping any hot air from directly recirculating into the radiator. But I feel that any air leaving the grille in one spot is likely to re-enter it a few inches over, so that is why I am still focused on reducing this problem. The deflectors definitely helped carry the hot air past the radiator, but they are not sufficient in my case.



I do have one question for anyone willing to take a swing. If I were magically able to seal the entire engine compartment front left to right and top to bottom (hood/bonnet to frame cross member) in the plane of the radiator, do you think I am going to create other problems by not allowing cool air to entire the engine department when driving? In my hypothetical situation, the air entering the carbs will likely have just come through the radiator. In my car as designed, there is so much leakage of of air around the radiator that I bet when driving, the carbs are able to get somewhat cooler air which simply blown by the side of the radiator. I don't want to solve one problem and create another.

 

[Jack T]

I think Ray's suggestion for adding the deflectors on the sides of the radiator to create a cowl effect for the fan can help. I plan to add those, in addition to the panel I fabricated to span between the frame rails in front of the radiator to prevent air coming through the grille going beneath the radiator. Other than the small deflectors in front of the radiator, the Healey has nothing in place to help manage airflow from the factory. Quite a contrast to my E-Type, which has numerous baffles and panels in place to maximize airflow through the radiator.

 

[shortsguy1]

Here are some of my direct measurements using thermocouples attached to the radiator. For simplicity, I am only showing radiator inlet temperatures (in degrees F). You can see the lack of an effect of closing off the coolant bypass.



Runs 1 and 2 had the radiator in stock arrangement. Runs 3 and 4 had the air flow reciculation addressed with my ugly plastic and tape shown above. I am not presenting any data from the fan shroud arrangement, because it clearly had more recirculation than the option measured here in plots 3 and 4.

The lower initial temps (for 3 and 4) may only be indicative that I got better at hooking up my thermocouples quickly. Or maybe the engine temp was a little lower when pulling into the garage. Regardless, you can see the slope of the graph is slightly different and that (for 3 and 4) the slope is flattening out at higher temps. The stock arrangement shows no trend of ever reaching steady state. So reducing air recirculation through the radiator is a good thing. I know, truly shocking results.

(sorry if I am overposting. I am simply documenting all of my findings, in case they help someone else someday)

 

[Jim 58 BN6]

Steveg addresses dealing with "reverse air circulation" (and many other things!) on his web site:

https://www.pbase.com/stevegerow/healeyaircontrol&page=1

Not original, but it apparently works.

 

[Patrick67BJ8]

Geoff Healey wrote a paper on the Heat being recirculated from the engine compartment to the radiator. Anyone have Paper this to post?

 

[4 on the floor]

I have a shop fan with slightly bent fan blades. (at the tip of each blade) The air, when fan is running running flows back and not off the tips of the blades. Would this help an over heating problem by blowing air back instead of to the sides?

 

[steveg]

....(sorry if I am overposting. I am simply documenting all of my findings, in case they help someone else someday)

Not to worry - IMO this is Forum GOLD!!