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Is it a bad idea to buy a higher pressure radiator cap?

shortsguy1

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As you all probably know better than me, I believe Healey's had either 4 psi or 7 psi radiator caps. I recently found a source of 10 or 15 psi radiator caps that would work with the 1" long neck of an original healey radiator. They look identical to the caps sold by Moss (Made in England), so I would bet they are made by the same company.

Here is the link to one of them:
https://www.carbuildersolutions.com/uk/long-reach-radiator-cap-spring-steel-upper-seal

My BJ8 with a rebuilt engine, new radiator, new metal fan still gets too hot when stuck in very heavy traffic. I am just looking for some added comfort at these rare times, to enable me to drive off the freeway if the needle hits 130, instead of having to turn off the car in the middle of the road.

Do you think the wear and tear on the cooling system would be much higher with 2X the pressure in the system? I have looked into fan shrouds and electric fans, but I haven't read much discussion of uprating the pressure of the cooling system.

Thanks in advance.
 

steveg

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Andrew, Do you mean 230?

An oil cooler will do more to lower the temperature. There was discussion a while back - the 7 lb cap is the way to go, but if you add an upper gasket, you can recover from a recovery tank.

Look up one of the old threads on coolant recovery tanks.

Your engine may run cooler when broken in.
 

Keoke

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I do not understand your problem . For example an operating temperature of 130 Degrees is too cool for this engine ??
 

bdcvg

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Not sure what extra pressure would do for You anyway. All those small hoses getting almost 2x the pressure built up inside them makes My right leg feel afraid.
 

BJ8Healeys

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You may find, as I did, that the radiator will eventually spring leaks at 15 psi. When I bought my BJ8, it came to me with a 15 psi cap. I didn't know anything about Healeys at the time, but I knew that American cars used a 15 psi cap so I didn't pay any attention to the cap as a problem. My radiator kept developing leaks until I learned that it was a 7 psi system and changed the cap. No more leaks.

I struggled with engine heat for years, trying every solution I could think of without success -- cleaning the coolant passes during engine rebuild, all kinds of multi-blade fans, different thermostats or no thermostat, radiator shroud, coolant overflow system, Water Wetter -- until I had the radiator re-cored with a modern core with more tubes and fins and installed a 190-deg. sleeved thermostat. Problem solved for the last 10 years. The car never goes over 190 on the gauge except on very hot days stuck in traffic, and then only to about 200. Typically, even in summer, the gauge runs at 170-180 and only goes up higher on really hot days.

Anyway, raising the system pressure to 15 psi would not make the engine run cooler. It would merely allow the coolant to get hotter before it began to boil.
 
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Assuming you meant 230: What Steve and others say is correct and raising the boiling point is not a fix but rather a potentially bad band-aid.

Engine temperature is an eternal problem for lots of cars, though some seem to lead a charmed life. I have struggled with it on my 100 over the years and found that every little bit--a new core, a better flex fan, an auxiliary 12VDC fan, proper timing, a recovery tank--helps. Sheet metal shrouding is on my list of projects for this winter.

My car is a lot better in high heat/traffic than when I got it and normally operates at around 170 but I try to avoid situations where I will meet a lot of stop and go driving.
 
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shortsguy1

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Oh, sorry about the typo. Yes, I definitely meant 230 F. My other car has its temp gauge in Celsius and I guess I had that in my head as I wrote last night.

Thanks everyone for your thoughts and suggestions. I had missed those previous articles mentioned, so I will need to go back and read those.

According to the supplemental instructions for the Moss version of the Texas Kooler fan, some BJ8s originally came with 10 psi caps. I have no idea if that is correct. Has anyone heard this before?

Given that almost every car on the road today has a 15 psi radiator cap, I guess I didn't see it as a band-aid. It just seems like we are handicapping ourselves by allowing our coolant to boil at a lower temperature than most cars on the road today. But it is great to get others' perspectives.

The hoop stress of a cylinder under pressure (like our coolant hoses) is proportional to the radius of the hose. So the stress is actually greater in the larger radiator hoses, which is why they tend to be thicker than the smaller hoses. I have only replaced the main radiator hoses (not the smaller coolant hoses) so far, but they seem no thinner/weaker than the radiator hoses I have encountered on cars running 15 psi systems.

Just to quantify this a little, pure water boils at 212 F with an open system, 224 with a 4 psi cap, 232 with a 7 psi cap, 239 with a 10 psi cap, and 249 F with a 15 psi cap. Adding ethylene glycol will increase those numbers, but reduce the specific heat of the fluid, so that has both a positive and a negative effect on cooling at the same time. The boiling point of a 50/50 mix of water and EG with a 15 psi cap will be 265 F.

I have never replaced the water pump on a Healey engine. But I imagine there is some seal around a shaft which could leak at higher pressures. Regardless of radiator cap, are leaky water pumps a common problem? For me, this is the aspect of using a higher pressure cap with the most risk.

Thanks again everyone for your help and sorry about the typo. Good thing I am not sending any spacecraft to Mars with my muddling of unit systems.
 

Jim 58 BN6

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"I have never replaced the water pump on a Healey engine. But I imagine there is some seal around a shaft which could leak at higher pressures."

Or lower pressures as well. It is British, after all.

I know it's not Healey, but I did add a coolant recovery system to the TR4A. I used to have to regularly add coolant, but no more. I also run a TR6 Fan, and had the rad re-cored with a modern one-more rows, I think. All that has made a big difference, and has greatly helped engine cooling.

I believe there was a thread a while back about adding air deflectors behind(?) the rad in a Healey to help air flow (someone with a better memory than me should chime inhere). I understand it gets really turbulent in there, and air doesn't efficiently move through the radiator.

My '58 is still far from running, so I'm really interested in things like this. GL, Jim
 
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John Turney

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One can tell those Healeys that have the higher pressure radiator caps: the radiator head tank bulges out instead of having flat sides.

As for air deflectors, mine are in front of the radiator and extend within a half inch of the grille. I also have a recored radiator, Texas Cooler fan, sleeved thermostat, rally vents and don't go above 200F, even when it's 100F+ out.
 

Jim 58 BN6

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One can tell those Healeys that have the higher pressure radiator caps: the radiator head tank bulges out instead of having flat sides.

As for air deflectors, mine are in front of the radiator and extend within a half inch of the grille. I also have a recored radiator, Texas Cooler fan, sleeved thermostat, rally vents and don't go above 200F, even when it's 100F+ out.

That's good information, John. I always thought the rally vents would be a big help. What exactly is a "sleeved" thermostat? Never heard of that before this thread. Thanks, Jim
 
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That's good information, John. I always thought the rally vents would be a big help. What exactly is a "sleeved" thermostat? Never heard of that before this thread. Thanks, Jim
It's an obvious visual characteristic of their construction, also referred to as a bellows type thermostat.

IMG_1026.jpg


IMG_1027.jpg


IMG_1029.jpg


IMG_1031.jpg


IMG_1033.jpg


IMG_1034.jpg
 

Jim 58 BN6

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Randy, thanks for the pictures, that explains it. Why does it work so much better than a standard type? It looks like the coolant flows around the perimeter, rather than through a central opening, maybe less restriction to the flow?

(Not trying to hijack the thread, just curious while you-all are paying attention). Jim
 
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I've forgotten more about it than I remember, but it has to do with a bypass hole cast into the head; the sleeve blocks it so all flow is to the radiator, when required.

If I'm wrong in the verbiage, I am counting on someone to correct it.
 

CraigC

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Jim, if you take a look at the pic where Randy is holding the can of Hylomar, you should see a rectangular passage on the far wall of the head inside the thermostat opening. That passage leads back down through the head and block to the inlet side of the water pump.(have you ever wondered what that hole on the right side of the pump mounting face was for?) When the engine is cold, the "sleeve" is below that port and coolant gets recirculated in the engine with out going through the radiator. In other words, it "bypasses" the radiator. As the coolant temp rises and the thermostat opens, the sleeves comes up and blocks off the "bypass" passage so that all of the coolant now must pass through the radiator. Running a non-sleeved t-stat will allow a percentage of the hot coolant to be recycled straight back into the block. If one is having issues with a hot running engine, trying a sleeved t-stat might not be a bad first repair attempt.
 
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Jim, if you take a look at the pic where Randy is holding the can of Hylomar, you should see a rectangular passage on the far wall of the head inside the thermostat opening. That passage leads back down through the head and block to the inlet side of the water pump.(have you ever wondered what that hole on the right side of the pump mounting face was for?) When the engine is cold, the "sleeve" is below that port and coolant gets recirculated in the engine with out going through the radiator. In other words, it "bypasses" the radiator. As the coolant temp rises and the thermostat opens, the sleeves comes up and blocks off the "bypass" passage so that all of the coolant now must pass through the radiator. Running a non-sleeved t-stat will allow a percentage of the hot coolant to be recycled straight back into the block. If one is having issues with a hot running engine, trying a sleeved t-stat might not be a bad first repair attempt.
Thanks for having my back; just couldn't compose the proper description, in between welding and fresh air breaks__what; isn't everyone still in the shop at 11:00 PM?!?!
 

Jim 58 BN6

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Thanks Craig, I see the opening you mention. This all makes a lot of sense, and I'll make sure to remember this, along with some of the other mods, when I get that far along with my car. You guys are always an encyclopedia of Healey knowledge! Jim
 

RDKeysor

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Since I was too tight to buy the really expensive sleeved thermostat, I installed the Moss "Thermostat Bypass Blanking Sleeve," part no 434-135, page A26 in the current catalog at $14.79. I wasn't able to assess the benefit of this installation, as I had done a couple of other changes to bring down the running temperature. The first of those efforts, as most people find, is to have the radiator recored. My result wasn't dramatic! My car is now operating at a reasonable temperature in Florida's hot weather, but like most owners, I'm still wanting to avoid idling the car in hot weather. Most recently I fabricated an air scoop below the sway bar on my BN7 based on Steve G's design and found on his very useful Web page. I made my scoop in the same pattern as Steve used, but extended it back to the frame member. I haven't done a full assessment of the results, but it didn't entail any alterations to the car, using the two existing threaded holes in the frame member for attachment. No one has commented to date on another unproven cooling tip I gained from someone at the Brit car show in Safety Harbor, FL, a couple of years back. This entails shimming the bottom of the radiator away from the frame member, theoretically allowing more cooling air to reach the bottom of the radiator. The factory did put ports in the frame member in that area, likely for cooling purposes. I used short sections of electrical conduit and longer bolts to provide the shimming. It's not noticeable unless you look at the lower radiator attachment points. I intend to eventually follow Steve's design to prevent heated engine air from recirculating around the periphery of the radiator and recirculating through the radiator. This all relates to the under-hood pressure issue that even hood louvers don't seem to cure. This is the most endless of Healey care issues.
 
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shortsguy1

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Just to answer my own question that I posed a few days ago, according to Anderson and Moment (in the Austin Healey Restoration Guide, p. 152), during BJ8 production, the 7 psi cap was replaced by a 10 psi cap. It isn't clear to me if all BJ8s came with 10 psi, or if it was in the middle of production.
 
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