Cooling system - thermostat

[MarkA]

Hi all,

When I bought my 67 BJ8 a year ago, it was having overheating problems. It almost never ran below 210 deg. I had the radiator re-cored with a new core with an extra row. I back-flushed the engine, changed the water pump and replaced the american thermostat with a 160 deg sleeved bellows thermostat from Moss. I switched to a 6-blade fan from Moss and replaced the radiator cap with a new 7 lbs. cap. I also checked the temperature guage for accuracy.

After all of that, the car would run at 165 deg on cool days, but ran very hot ( > 210 ) in 80 deg weather. I changed the thermostat to a new non-sleeved 165 deg thermostat and blocked the bypass port. The temps stayed at 165 deg, even on hot days on the freeway. I then tryed the "modern" version of a sleeved thermostat (165 deg) from Moss without the blocked bypass port. Now the car runs at 150 deg in the cold California weather (60 is cold for California!). When the weather warms up to 75 degrees, the car runs at 165 deg.

I want the car to run at 165, at least. I think that 145-150 degrees is too cool to let the moisture in the oil evaorate. A warmer heater would also be nice. I also don't want to keep the bypass port blocked to avoid pocket boiling in the engine.

What kind of thermostat is everyone else having good luck with? Any suggestions?

Thanks,
Mark

 

[Keoke]

Hi Mark I am running a 160 Degree sleeved thermostat, love those cooler running temps on hot days in the summer. If necessary I block off a portion of the radiator with a piece of cardboard on real cold days.--Fwiw--Keoke

 

[MarkA]

So the cool runnng is a normal thing on cold days? I though the thermostat would keep the engine at the rated temperature.....

 

[tahoe healey]

Borrow or buy ($40 bucks) and infered temp sensor. Aim it at the area where the thermostat is and you may be supprised. I ran 160 with outside temps of 40 degrees (also in California) one week ago. Healeys use to be run with ski racks and chains with out problems. Last summer I ran at 190 with ambient temps at 90 to 95 degrees with stock fan. I have a sleeved 160. These temps were confirmed using the infered sensor (which I tested on an egg in boiling water as suggested on this forum) and set the car gauge accordingly.

 

[Keoke]

So the cool runnng is a normal thing on cold days? I though the thermostat would keep the engine at the rated temperature.....

Yes the cool running with your mods are to be expected the thermostat will not clamp the cars running temperature at the thermostats rating. The intent here is to speed up the cars warm up until the thermostat temperature is reached. Once that temperature is exceeded the thermostat opens and effectively the thermostats function is over. For the hot running engine its running temperature will continue to climb.---Fwiw--Keoke

 

[MarkA]

The six-bladed fan from Moss is very loud at any RPM other than about idle. I want to change to something else that might do a better job at low speeds, but then "get out of the way" at higher speeds.

The Texas Cooler get the recomendation from most people, but it is not available any longer. I have seen the posts about the Noch fan. Is that the right way to go and where can I find them?

Thanks...

 

[Keoke]

Yes the Knock fan is reportedly a better unit. However, IMOP any fan with an even number of blades will be noisy. There are some five bladed ones available ,but I do not recall a source at the moment. You can find Knock by searching for "British Car Specialties"====BCS--Keoke

 

[MarkA]

Thanks!

 

[Ed_K]

I have a 185' thermostat and want to try going to a 165 or 160.
I have not had this open yet to see what it looks like.
There is talk about a " sleeved " thermostat.
Can I use a generic napa thermostat or do I need to order a special kind from one of our usual suppliers ?
I am going on a trip this weekend and would like to buy one locally unless it is not advisable.
Thanks !
Ed K. /bcforum/images/%%GRAEMLIN_URL%%/driving.gif

 

[Dave Russell]

Hi Ed,
Some engines, Healey Sixes included, have a coolant bypass port in the engine. With the thermostat closed, coolant is circulated through the bypass port & through the engine only. Bypasses the radiator but is not completely stopped from flowing. When the thermostat opens, the original ones had a "sleeve" on the thermostat which moved to close the bypass port. Otherwise, some of the coolant would always flow through the bypass port & not flow through the radiator. If the cooling system was marginal for ambient conditions, this coolant bypass might cause overheating.

Sleeved thermostats cost quite a bit more but do assure that all coolant goes through the radiator when the thermostat is open. Whether you use one or not depends on just how hot your car runs, the phase of the moon, tide levels, & other intangibles. Seems like everyone has a different experience & opinion. It would be reasonable to use a sleeved thermostat as the car was originally designed. However, some sleeved thermostats seem to work better than others, so I guess the choice is yours. There are other work arounds such as permanently, partially restricting the bypass port.

Try a generic thermostat, if it works ok, if not order a sleeved one. I don't believe the unsleeved one will cause an emergency.
D

 

[MarkA]

Hi Ed,

I have tried different configurations. I had a 185 deg thermostat without sleeve and the bypass port was left open (from previous owner). I had problems with overheating on hot days (but also due to weak radiator). I had the radiator re-worked with a higher capacity 4 row core. At the same time, I changed over to a 165 deg bellows-type thermostat from Moss. I had overheating problems with it on regular days and under-heating problems on cold days.

I switched to a standard (un-sleeved) 165 deg thermostat and partially blocked the bypass port. Slower warm-ups (a little) but eliminated the overheating and under-heating problems. I then switched to a 165 deg wax-core sleeved thermostat from Moss. Faster warm-ups, no overheating, but runs cool on cold days. I attribute the under-heating condition to the thermostat starting to open at 150 deg.

All in all, I like the latest configuration and plan on keeping it. On hot days, it runs at 165 deg on the freeway or city streets. On cold days, it runs at 155 deg on the freeway or streets.

Mark

 

[Ed_K]

Dave and Mark,
Thank you both for your replies. Since I want to do something before this weekend, I'll try a generic 160-165' thermostat 1st but I'll keep in mind that I may need to get a sleeved one later...
I think I understand why the bypass passage is there, to help circulate the warming water from the engine up under the bottom of the thermostat so it will open as soon as the temp in the block gets up to the spec of the thermostat ? Otherwise the flow of warming water from the block may not be able to get up under the thermostat so it will open ? Or am I off base in this assumption ? If my assumtion is true, then just a little hole may be all that is required for this to function as designed. I guess I had better wait to see what kind my Dad put in 25 years ago..... Off to the parts store.
Thanks again !
Ed
..... Dave, Love the job you did on your engine rebuild !

 

[Dave Russell]

Hi Ed,
I believe that the thermo bypass provides for even cooling/warmup while the thermostat is closed. Otherwise, there would be some localized hot spots in the cylinder head & some relatively cold spots. Also it provides quick warmup for the heater water if that is important.
D

 

[Ed_K]

It had a 180' hinge/flap type that I have never seen before. Made in the USA. I put in a Stant 13006, 160' thermostat. I went for a test drive with the outside temp around 62' and it ran a consistent 20 degrees cooler than before. I had already installed a Knock fan..
I cannot believe it was that simple to lower the operating temp of the car by 20 degrees or I would have done this months ago. I guess I will have to wait for a hot day to see what happens but the first test was promising.
Ed

 

[Dave Russell]

Ed,
20 degrees cooler would be expected on a cool day.
If the weather is very hot it won't matter much if you have a 160 or 180 degree thermostat. If it's hot enough, the engine will still go to 190 - 200 or wherever. The 160 just starts from a lower temperature & takes a little longer (a few minutes) to reach 200. The only time the 160 will make much difference is if ambient temperature is low enough to keep the thermostat closed or partially closed. The real comparison would be on a 100 degree day. Keoke pretty much said this above.
D

 

[healeynut]

As someone who does alot of driving in a very hot climate, I will have to disagree a bit here.

A cooler thermostat will open much earlier and allow more coolant flow at hot temperatures. The only reason that people don't think it makes much of a difference is because your standard thermostat has a small opening and restricts coolant flow, so if the throat of the thermostat is small, it won't make much difference.

The Sleeve thermostats, if you can find them, are very good because they typically have a very wide mouth opening, allowing lots of coolant flow when open.

As a result, another option is to get a 180 deg Wahler thermostat which has a pretty wide opening as well.

Hope that helps.

 

[Dave Russell]

Hi Alan,
As I said above, "Seems like everyone has a different experience & opinion." Most of my driving here is in ambient temps that rarely exceed 110F. Don't know about Hong Kong.
D