• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

Sleeved thermostat....worth it?

Share this page

Merlin63Tr4

Merlin63Tr4

Jedi Trainee
Country flag
Offline
The question I have is, if you currently have no cooling/overheating problems with the normal replacement wax capsule thermostat in your Tr, is the fancy sleeved thermostat that the large vendors sell worth it ? /bcforum/images/%%GRAEMLIN_URL%%/confused.gif That thing is like 10X the price of the common replacement thermostat !!!!! /bcforum/images/%%GRAEMLIN_URL%%/shocked.gif

I'm in the process of gathering parts to do the thin fan belt mod, along with the elimination of the engine fan, addition of electric fan, alternator.....etc to my '63Tr4
And since I'm going to have to take some of the cooling system apart I was thinking of replacing the water pump, hoses, etc...... /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
 
I have been told by others it's not worth it unless you're in a cold climate where it helps on start up to stop the small incremental amount of water from exiting the bypass water hose until operating temparatures are reached.

If I've got that wrong somehow, I'll not in the least be surprised. However, I've been more than once told not to bother (I'm in Arizona), and if my car were operating fine and not overheating, I wouldn't buy the sliding barrel thermostat.
 
Hi,

Yes. The sleeved t'stat is definitely worth it if you intend to keep the bypass circuit as original. The sleeve covers the bypass when the t'stat is open (after the engine warms up) to insure most of the flow goes to the radiator, not back into the engine. With a standard t'stat in there, a lot of the coolant goes right back into the engine without being cooled in the radiator.

An alternative is to use a standard non-sleeved thermostat and partially block the bypass hose with something jammed inside it, like a washer of the correct size. Just be sure to leave a 1/8" to 1/4" hole for a small amount of coolant to pass easily.

Never run the 4-cyl. TR engine without some sort of t'stat in place. It will usually overheat if the t'stat is completely removed, supposedly because coolant moves too quickly throught the radiator without the opened t'stat in there to restrict the flow a little. Racers jam the t'stat in its wide open position. But, for street cars a working t'stat is a better solution.

There might be an alternative to the really expensive sleeved t'stat some vendors sell. I have heard that there is an identical sleeved thermostat used in some Land Rover models that sells for a lot less. So far I haven't been able to verify this or find out what model t'stat to use.
 
You are likely right, though it seems that if quick start up operating temperature is not an issue, and if you're not now overheating using a regular thermostat (without the sleeved thermostat), the regular thermostat should suffice. No? I've also heard that some people even use a regular thermostat and block the bypass with a plug. Here's an article discussing some related issues.


https://www.britishmotorclub.org/news/2002/Nov02.pdf
 
When I rebuilt my engine I put a partial block in the bypass by tapping threads and installing a plug with a hole drilled in it to allow some bypass. The advice came from a member of the Houston TR club that was helping me. He stated that in the summer I "could" have problems because a lot of the the water would not go through the rad. I run an electric fan with small belts. I have a 185 sensor in the bottom of the rad that controlls the fan. The fan comes on at 185 and is off at 180. We'll se how it holds up in the Houston heat this summer!
 
FWIW, I use a partial plug in the bypass hose. It's a 3/4" copper pipe cap with a 3/16" hole drilled in it. The idea of the hole is to not let the head get hit all at once with cold coolant when the tstat finally opens.

The hole seemed like a good idea so I added it, but I also ran for 20+ years with just a 1" section of brromstick jammed in the hose (no relief hole).

Can swear it helps with hot weather cooling but where I live I look for any advantage.
 
An old saying; If ain't broke don't fix it. If not over heating, don't worry about it.
 
Yeah, I know it's not really broken, but I'm about to do the thin fanbelt mod and I have to replace my waterpump because it has a pressed on pulley. I was just checking to see if there were any benefit to the sleeved thermostat. Since I'm going to have tear out the radiator, coolant pump,etc I figure I might as well replace all hoses and the thermostat as well. From the research I have done it seems like the sleeved thermostat would be of some benefit if not that then the addition of a plug with an orifice in the bypass passage would be almost as good. Thanks for all the comments.
 
Back
Top