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

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Hi All,

Here is a document "I Always Wanted a COOL Car" that I first wrote for our club and posted here a number of times.

https://drive.google.com/file/d/0Bwqddve6a2OTN2tlUHk2SWZPT1k/view?usp=sharing


Shortsguy1, to answer your question. Due to the Healey's design, sealing the engine compartment would be impractical, if not impossible, but sealing the radiator bulkhead would be difficult enough. Although I don't think you would incur additional issues if your efforts were successful, I have been wrong before (just ask my wife).

I have a TR7 roadster that was designed with an engine tub and a sealed radiator bulkhead. After modifying the engine, I removed the faulty air conditioning (a large York compressor) but left the 2 auxiliary fans which were mounted low and angled up toward the radiator (air streams hit the radiator fins on an angle for the greatest of cooling contact). I then eliminated the engine-driven multy-bladed fan, leaving only the 2 thermostatically controlled auxiliary A/C fans. With the louvered bonnet allowing easy hot-air escape, the car stays COOL even in a summer shore traffic jam or at a long traffic lights.

Hope you find something useful.

Ray(64BJ8P1)
 
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I tested an original bellows thermostat last summer while fixing a Healey with an overheating issue and compared it to a new Moss of the same type. I boiled both in hot water . They both started to open at the same temp but the new thermostat opened another 30% more than the original and both were fully opened at 195 degrees. Both opened to a larger port than a conventional top hat type thermostat. IMG_0256.jpgIMG_0262.jpgIMG_0277.jpgIMG_2500.jpgThe third picture is of the old radiator with a shop light up behind it . The fourth picture is of the new radiator. The car idled cool but quickly built up heat while driving. I used a new plastic fan from Healey Surgeons ( not exactly like the Texas cooler style which has one more blade)but the only readily available and a new radiator. I reused the original bellows thermostat as I didn't think that coolant flow was the problem , it was air flow over the radiator fins and a generally crummy 60 year old radiator that had an over accumulation of crap on the fins that prohibited heat transfer. IMG_2512.jpgThe car now idles at 190 when its 95 outside but the temp drops as soon as its underway again.
 
Thanks everyone for the suggestions of what has worked for you. Your experiences motivated me to try to document the effects of some of the things you have tried. I will put up some graphs of my results from yesterday at some point, but here are my main conclusions.

1) Getting good data is hard because of the changing environmental conditions (ambient temperature and perhaps wind speed).
Despite this, I feel comfortable saying:

2) Blocking the engine compartment in the plane of the radiator from left to right and below the radiator to the cross member (with semirigid plastic sheets and tape as a temporary solution) has substantially reduced the amount of recirculation. This resulted in lower radiator air intake temperatures, larger changes in temperature of the coolant through the radiator (now 10 deg, up from 6 when we started), and longer times until too high radiator coolant intake temps were reached.

3) Putting a rolled up tower on top of the radiator to fill the gap between the radiator and hood/bonnet had a measurable improvement. I didn't really believe this one, so I ran the test multiple times. But basically, a lot of hot air comes back over the rad when that gap is present.

4) Doing these changes to the engine compartment has a very small impact on the temperature of the air going into the carbs (just a few degrees at most). By clogging all those holes/gaps in the engine compartment, it is reducing how much cold air can get to the carbs just slightly when underway. But at idle, the air temp at the carbs is improved by all my changes (again, just slightly). I guess my point is that these changes to the air flow on the radiator has NOT dramatically changed air intake temps into the carbs, so thankfully I haven't created a new problem.

5) Speaking of which, the actual temps of the air into the carbs was interesting. I measured about two inches in front of the rear carb air filter. Ambient T was 90 F. Coasting down a long hill, the lowest the carb intake temp got was 130F. During cruising on a flat stretch of road at 50 mph, the carb intake temp was 140-145. At a stop light, the car intake temp jumps almost instantly to 150 and then climbs from there. In my mom's garage, the carb inlet temp would be 160-170 within a minute (her driveway is uphill) and would reach 190F several minutes later as I ran my tests. So not relevant to my efforts, but if racing or power is important to you, getting those engine carb intake temps down would be beneficial.

6) For the next three tests, I tested additional underpanels to the car to see how that affects things. During my prior tests, I could feel and measure hot air coming down under the radiator from the engine side of things. To start with, I used by corrugated plastic sheets to cover from the front valence to the cross member and then from the cross member back about 18 inches. So this was two underside flat sheets of material, one forwards of the radiator and one back from the radiator. These shields have a measurable impact on how fast the car overheats at idle.

7) Next I removed the front shield, so of the underside panels, only one panel was in place and it went from the crossmember rearwards. This shield does not seem to help with cooling at idle when parked.

8) Next I reinstalled the front shield and removed the rear shield. So of the underside panels, only one panel was in place and it went from the cross member fowards towards the front valance of the car (to basically underneath the front bumper). This shield DOES seem to help with cooling at idle when parked. Unfortunately, I was not able to tell from my data if two shields is better or worse than only the front shield. The data was similar enough that any differences could have been just ambient changes.

So for my car, clogging the path of recirculating has shown dramatic effects. It is not perfect, but substantially better. Now with all this extra plastic installed, red lights don't worry me. Before it would overheat so fast that even a longer red light could cause excessive temps. When I started all this a few days ago, the radiator coolant intake temp would reach 220F within 3-4 minutes of parking. Now it takes 8 minutes. So traffic jams would still be a problem, but city driving with long red lights should now be more manageable. I have seen how others have made my temporary changes into a permanent solution, so I may follow in those footsteps, but that is a battle for another day.

I have a few more tests planned today so I will report back later or tomorrow. Thanks for reading.
 
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Shortsguy--

Your tests are certainly interesting and one of the projects I have never gotten around to doing is the fabrication and installation of ducts/baffles to maximize the flow of air through the radiator and minimize its coming back.

Your observations in paragraph 5 regarding your car's heating up almost instantly, however, point to an underlying problem which needs to be addressed in addition to air flow, and if you work on the ability of the cooling system to better dissipate heat I believe your car will be much more able to tolerate both more load and less air flow. In other words I believe you should deal with the source of the problem rather than trying to compensate for it.

Whatever, keep us posted.
 
4 on the floor:
After reading your post, I did some research on whether winglets would improve the performance of a fan. It seems like the jury is out on that one. I found research articles suggesting that winglets on the end of the fan blades both would and would not improve performance. A proper fan should with relatively low clearance between the fan tips and the shroud is universally understood to improve fan performance. So winglets might help, but if I am going to control air flow off the ends of the fan blades, I will do it with a proper fan shroud.

Michael Oritt-
Thank you for your thoughts. Yes, after doing this work this week, it does suggest something else is wrong. The engine is new with passages cleaned. The radiator is new. It has the "best" fan. So that leaves water pump as a problem, the engine timing, or the air/fuel mixture. My prior experience with classic cars is with old diesel mercedes vehicles (which have neither carbs or distributors), so I am scared of both of those items on a Healey. They are to be both feared and respected. I sort of hoped that the mechanic who installed the engine would have adjusted both the timing and the carbs after engine installation, but I never explicitly asked. But yes, I think I need to get over my fears and mess with those. It wont happen this visit to the car, but hopefully soon.
 
My Thursday was not as productive as I had hoped. I had planned to compare air flow at the front grille with both the BCS/Derale stainless flex fan and the Denis Welch/BMW red plastic fan. But access to the fan bolts was limited enough that I could not do so easily. For others who have swapped their own fans, is the job better performed with the radiator out? My bolts were long enough that they were backing up into the cardboard I was using to protect the rad core. At that point, rather than work without the cardboard, I just gave up on the swap and decided that radiator removal is probably "easier". Any thoughts?

So instead, I drilled two decent sized holes in the thermostat to see if water flow might be the issue for me (indicative of maybe a water pump issue) . I was curious if I could increase water flow rates at idle (and underway) while still enabling the car to properly heat up and operate. The hole size was randomly chosen. My car has a 160 F thermostat and on an 85 degree day (the weather has cooled off dramatically compared to the start of the week). It was still able to reach 160 F while idling in my mom's garage. I didn't time it (because the weather is so different), but common sense would dictate it will be slower to heat up. Underway, the car was 160-190F. Unfortunately, with ambient conditions so different, I cannot really conclude anything about my water pump. But it appears that even with the two holes, the thermostat is just able to control the coolant temperature. Any lower ambient temp, and I suspect my drilled holes will be too large.

But this got me to read up further on thermostats, and if random internet opinions are the things that matter, running my engine at 160 F is probably a bit cold. I could find no hard evidence on the topic. But regardless, I plan to buy a 180F thermostat and run a similar test down the road. I would love for my car to live primarily between 180 and 200F for most of the time. If the drilled 180F thermostat is still able to keep the car at 180F, I may end up using a drilled 180F thermostat in summer and an undrilled 180F thermostat in winter.

My visit to my car has come to a close. This was an unusual week for me because I had access to the car, but wasn't physically able to do any projects requiring substantial strength. Once back to normal physically, I would much rather spend my time replacing the rear leaf springs (which are sagging on the drivers side) and fixing the brakes (which require an awful lot of force to get the car to stop). But this was an interesting week for me and I very much appreciate everyone's help and advice. I think tackling the engine timing and carburetors will be important tasks for me to get over my fears. Thanks again.
 
I regret not reading this thread sooner. Coming from a background of industrial instrumentation and process controls, I am impressed with your methods of testing; to purgatory with guessing, measure the conditions! Twenty (30?) years ago, I wished there was a way to put a multi-point chart recorder in my car__I wanted to monitor everything (did you know that there are sparkplugs available with quartz pressure sensors in them to record the BMEP of each individual cylinder?). But I digress!

Several of the points mentioned here, certainly some early in the thread by Ray, have been incorporated into my car (100/6 2-seater with 29D engine, Isky T3 cam, flowed/matched head, 3X 45 DCOE carbs, Jett-Hot coated tube headers & Mallory/MSD ignition; to set the stage) and I am currently living in southwest Florida__where it's NOT a dry heat__though when most of these mods were first done, the car and I were in southern Louisiana, another hot, tropical climate.

My car does have what was then (circa 1979) called a competition TX radiator core, and it holds fully 1-1/2 gallons more water than the radiator (core, same tanks) it replaced. Highest number of fins per inch, blah, blah, blah. From memory, I believe its staggered rows are 4-3-4-3-4-etc (tubes, front to back).

Thermostat__I think__is a 170*, at least that's what it mostly runs at (Nisonger rebuilt the safety gauge some years back) although under the worst conditions, it will almost reach 190*.

Because at one time I had a strut brace between the shock towers and couldn't run a mechanical fan, I put a Kenlowe thermostatically controlled electric fan in front of the radiator. That wasn't quite enough to cope with city traffic, so off with the brace and one with the original type Texas Cooler fan. I've kept the electric fan too, and most of the time I come to a stop after any amount of driving, it's running (I don't recall the t/stat's setpoint; maybe it could be set higher...).

I do have fender mounted air-outlet vents, and I can tell you that the heat pours out of them, so that alone should end any comparison to your car's cooling issues.

But the one (1) thing I did do was fabricate a stainless steel duct directing air into the radiator opening__and isolating the air exiting the oil cooler__from immediately behind the grille bars, essentially what Ray described.

Various pictures, hoping to present the duct as a whole...

Radiator & oil cooler apertures (edges of duct are visible in hi-res image @ ends of lowest grille tube after clicking to magnify: https://spcarsplus.com/gallery3/var...new_hubs-wirewheels/IMG_7619.jpg?m=1304199713 ).

Note: snow was during brief interlude living in Ohio, though I have seen snow in both LA & FL before!

IMG_7619.jpg


Cross-section, looking in from the LH wheelwell.

str_002.jpg


IMG_6515.jpg

View from RH wheelwell.

IMG_6516.jpg


I don't know if this will be of use to you, but based on your findings thus far, to pursue ducting air into the radiator while eliminating/minimizing recirculatory air wouldn't be a waste of time.
 
I found a paper written by Geoff Healey about the engine compartment temp.
 

Attachments

  • Engine Cooling -Geoff Healey 1991.pdf
    757.9 KB · Views: 183
Shortsguy--

If you have not verified that your timing is correct you should address that ASAP. Aside from the fact that too much advance can cause overheating it can also cause engine damage.

SU carbs are about as simple as you can get and if you don't feel like dicking around with points get yourself a Pertronix or similar system--AFTER you deal with the timing!
 
Hi All,

Patrick, the article by Geoff Healey is one I wish I had a long time ago as it shows the problem and cause was known for quite a while. But I guess discovering it for ourselves was not a bad thing. It also points to the thought I had prior that maybe we are over pressurizing the compartment with large aggressive fans that only force the air to recirculate faster...especially when not baffled to help direct the air rearward. As mentioned prior, I am beginning to wonder if my original yellow 4 blade Healey fan would be sufficient and maybe the more aggressive Texas Cooler now mounted moves too much air and just exacerbates recirculation (especially without fender vents or bonnet louvers). As Geoff indicated, the more aggressive fan increases air pressure within the engine compartment and reduces the pressure in front of the radiator. This condition only amplifies the dynamics of hot air recirculation and does nothing for cooling.

Randy, as always, your work is impeccable, well though and implemented.

As I am beginning to conclude, adding recirculation blocks without managing air flow and, most important, escape would be a waste of time. Although I am beginning to favor the front grill-to-radiator duct as being the most practical approach to greatly reduce the % of recirculated air, the low pressure opening is only moved further forward and would still reside within the outer limits of the forward escaping hot engine compartment air.

Again, without fender vents and/or bonnet louvers, there must still be a balance between engine compartment air flow escape and volume drawn in by the fan. This balanced flow, along with the discrete use of baffles to help direct the flow to a rearward escape, would greatly diminish, if not eliminate, much of the underlying cause of recirculation.

As a side note, I only began to realize the issue of recirculation after installing the bilge blower in my cold air duct. I first turned it on at a traffic light one summer day and was presented with HOT non-cool air.

That's all I have now,
Happy 4th of July,
Ray(64BJ8P1)
 
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Randy
Great job with the duct work. It looks like factory.
I don't own a "Big" Healey just a little BE, however after proper sealing/ducting my radiator and oil cooler I saw a drop of about 20 degrees at 70 mph to 190 on a hot day .
Getting air into the rad is not just a traffic light thing.
 
I was adjusting the camber on the car yesterday and while placing the jack under the spring plate I found Myself staring at the space in front of the bottom of the radiator. I thought it would make sense to fabricate a scoop of sorts to scavenge air from under the front bumper and push it up to the bottom of the radiator. I wonder now if that might at least slow recirculating air from going under the radiator. I also wondered if there were some way to fabricate ductwork of some kind further back that might pull air out of the engine compartment from the bottom of the car. Something no lower than the mufflers.
 
Hi bdcvg,

Keep in mind that recirculation is a problem when the car is at rest or moving forward very slowly. When under way, the big issue is stopping air from pressurizing the engine compartment and diminishing the passage of air through the radiator...especially if the car does not have fender vents or bonnet louvers. To start with, take a look at the document I previously posted and look at the sections addressing the blockage of air from passing between the cross member and bottom tank. Additionally, take a look at the panel placed across the frame between the cross member and around 6" before the crankcase that is meant to stop incoming air from disrupting outward flow. I later installed an additional panel across the bottom of the frame between shroud and air block to provide a bottom director the side deflectors leading to the radiator to also help direct the flow of air to the radiator. Although all seems to have worked quite well, I now believe my efforts in front of the radiator would have been better served with a fully enclosed duct between grill and radiator face however still keep the 2 panels stopping air intrusion into the engine compartment from below.

Ray(64BJ8P1)
 
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Hi Shortsguy1,

I too have struggled with the cooling on my BJ8 Healey.

To determine if its the cooling air/recirculation, I tried simply putting a shop fan in front of the radiator like the shops will do when testing cars. This will increase the air pressure in front of the radiator slightly, eliminating side drafts from behind the radiator. If this significantly improves the idling temperatures then you are moving in the right direction.

Secondly, I originally discounted the ignition advance being a possible culprit. So I tested the theory and here are the results:

View attachment ign timing overheating.pdf

As you can see, only 5 degrees had a significant impact.

Also, I too had my radiator re-cored when restoring my BJ8, a 3 row 'modern' core which had louvered fins of serpentine construction. While it was satisfactory at speed, it was woefully inadequate at idle. I currently have a 5 row staggered tube, flat finned core which only required minor modifications to the steel braces which solder between the tanks. The car now behaves itself in 95 degree plus weather. Also I had installed a Kilmartin shroud, and Flexilite 415 nylon fan to get the air flows at idle up to what a modern car has. If you are interested in the details and/or selection processes, please pm me off list (g.rude@q.com).

As for the water pump, I did flow tests to see if it was up to modern standards (it was after mods...I have details but they are in the archives too). But also, mine was a 'repop' pump which had the impeller too shallow in the block AND the impeller had less discharge area than a original pump. Also, my block apparently had a small core shift and the pump housing had to be machined so the impeller would sit deeper in the block to achieve proper alignment. Anyways, I did not measure before and after with the pump mods, unfortunately, but the testing confirmed the original pumps are sufficient in flow compared to a modern engine (at least in my research).

I hope this helps,
 
I'm with You Ray and have read Your informative post on cooling. Think about a flat panel covering the bottom of the back half of the engine compartment with an electric fan pushing air down. Would that evacuate the engine compartment of recirculating air?
 
Regards adding an air scoop, Steve G illustrates just such a scoop on his Healey site. You will recognize him as a major contributor to this forum, and I always pay attention when he comments on our many Healey issues. I fabricated my scoop from a stainless steel sheet metal piece from a gas grill I was discarding. My sense is that it is helpful when the car is under way. I used the existing bolt holes on the inside of the frame rails to fasten the scoop made in similitude of Steve's design. I think it contributes to the incremental gains I have made have made in bringing my car's heat issues under control. I may eventually duplicate Randy's very nicely done oil cooler modification to combat what seems to be a noticeable temperature increase with relatively long distance driving on my BN7. Shortsguy's airing of the discussion is very helpful, but I sense the extremely rapid temperature increase he is getting with his car is peculiar to his car.
 
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