TR2/3/3A Further to "plugging the thermostat bypass hose"/

[karls59tr]

I remember this being discussed before but can't remember if the members here thought this was a good idea to aid cooling? Seems to me something was said about it not being good for the cylinder head?

 

[Sarastro]

I wouldn't. The bypass hose allows coolant to circulate before the thermostat opens. That keeps the temperature distribution throughout the engine more or less constant. Without it, you would get hot and cold spots in the engine until the thermostat opened.

Also, the bypass feeds coolant into the thermostat housing. That's what heats the thermostat so it opens. Without the bypass, the thermostat might not heat up and open until the coolant in the head was really too hot.

I don't understand why anyone could see an advantage in plugging it.

 

[Geo Hahn]

The advantage occurs if you are not using the original style thermostat with a blanking sleeve that closes the bypass when the thermostat opens.

Without that blanking sleeve a fair amount of coolant returns to the engine without having gone through the radiator. It's a bigger issue on the TR3 as STC realized the possible problem and greatly reduced the size of the bypass opening on the TR4 tstat housing.

Particularly in a climate (or seasonal usage) where quick heat from the heater is not a priority it can be a good trade off.

Probably prudent to have a small hole in the blockage so some heated coolant is circulating before the tstat opens but not really necessary in my experience. I used a piece of broomstick (no hole) for a couple of decades before changing to something a bit more elegant:

 

[karls59tr]

Is that from a plumbing supply shop? Is the center hole about 1/4" wide?

 

[bobhustead]

Best way to improve cooling by tinkering with water flow is simply to remove the thermostat. The sole purpose of a thermostat is to speed up reaching operating temp, with a side effect of slightly to radically increasing operating temp, depending on condition of water jacket and radiator. A clean water jacket will make more efficient heat transfer to circulating water and a clean radiator will make more efficient transfer of heat from circulating water to radiator, while good air flow is needed to carry that heat out of the radiator. When you consider opinions on the operation of cooling systems, consider the law of conservation of energy. Randall Young did a good post on this years back. You can probably find it using the search feature. I ran my original TR3 in Miami, Fl. for 3 years and my current 3 in NC for 10 with no thermostat. Both cooled like a charm.
Bob

 

[Geo Hahn]

Karl - As I recall it's a ¾" cap with a 3/16" hole.

...remove the thermostat. The sole purpose of a thermostat is to speed up reaching operating temp

Maybe okay in Miami but I think Karl is in the frozen north (Canada) where an engine may need a thermostat to achieve proper operating temperature.

 

[bobhustead]

Definitely needed in winter to get heat in the car more quickly. Wait, what am I saying? This is a TR3 heater.
Operating temperature where the work is done (combustion chamber) doesn't change much with regard to water temp. My car runs fine when the temp gauge is on 90 and when the temp gauge is on 160. My main point is that if you burn a quart of gas in the combustion chambers you get a fixed amount of heat and that exact amount of heat needs to be dissipated by the block directly radiating to air and by the radiator transferring the rest of the combustion chamber heat to the air. You can't destroy the heat; you can only transfer it to another medium. A lot of ideas we hear about how a cooling system works, what is wrong with it, or how to fix it don't take this principle into account.
Bob

 

[Hamish Racing]

I did this mod
It allows the engine to warm up better in more temperate climates. As once it’s up to temp the thermostat kicks in and regulates as normal. As has been mentioned without the sleeved bellows thermostat with the blanking parts.
I think the casting holes in the later tr4/a cars is smaller so triumph had some learning over time.
I used a 22mm plumbing end cap that the hose fits over.
Hole intentionally drilled at the top for air bleed reasons.
Does no harm.

 

[karls59tr]

Karl - As I recall it's a ¾" cap with a 3/16" hole.



Maybe okay in Miami but I think Karl is in the frozen north (Canada) where an engine may need a thermostat to achieve proper operating temperature.

 

[Geo Hahn]

My car runs fine when the temp gauge is on 90 and when the temp gauge is on 160.

Well we'll just have to agree to disagree on this. The engine may run fine but I think you need it to get up to operating temperature to (among other things) rid the oil of any moisture (e.g. from condensation).

 

[karls59tr]

I did this mod
It allows the engine to warm up better in more temperate climates. As once it’s up to temp the thermostat kicks in and regulates as normal. As has been mentioned without the sleeved bellows thermostat with the blanking parts.
I think the casting holes in the later tr4/a cars is smaller so triumph had some learning over time.
I used a 22mm plumbing end cap that the hose fits over.
Hole intentionally drilled at the top for air bleed reasons.
Does no harm.

Is the air bleed hole abouut3/8"?

 

[karls59tr]

I don't think I'd run my car without a thermostat. I go with 15% water wetter,25% antifreeze and 50% water and don't have overheating issues. It can get up to 35 degrees Celsius here in summer. I don't use the car in winter.

 

[Sarastro]

Hmmm. I thought it was a given that you should have an orifice in the bypass hose if you use a modern thermostat. That's how my TR4A is configured. I'd prefer to use the original type of thermostat, which shuts off the bypass when the car is warm, but they don't appear to be available any more except perhaps at outrageous prices. Yes, with the orifice you are theoretically bypassing some coolant while the engine is warm, but it's minimal--the orifice's restriction is way more than the radiator.

Well, maybe some have gotten away with it, but I still wouldn't try it. I think it's a risky practice for little benefit.

 

[karls59tr]

Hmmm. I thought it was a given that you should have an orifice in the bypass hose if you use a modern thermostat. That's how my TR4A is configured. I'd prefer to use the original type of thermostat, which shuts off the bypass when the car is warm, but they don't appear to be available any more except perhaps at outrageous prices. Yes, with the orifice you are theoretically bypassing some coolant while the engine is warm, but it's minimal--the orifice's restriction is way more than the radiator.

Well, maybe some have gotten away with it, but I still wouldn't try it. I think it's a risky practice for little benefit.

Are you saying that plugging the bypass could cause restriction resulting in pressure that could cause leakage say on an older radiator?

 

[NeilRogers]

Best way to improve cooling by tinkering with water flow is simply to remove the thermostat. The sole purpose of a thermostat is to speed up reaching operating temp, with a side effect of slightly to radically increasing operating temp, depending on condition of water jacket and radiator. A clean water jacket will make more efficient heat transfer to circulating water and a clean radiator will make more efficient transfer of heat from circulating water to radiator, while good air flow is needed to carry that heat out of the radiator. When you consider opinions on the operation of cooling systems, consider the law of conservation of energy. Randall Young did a good post on this years back. You can probably find it using the search feature. I ran my original TR3 in Miami, Fl. for 3 years and my current 3 in NC for 10 with no thermostat. Both cooled like a charm.
Bob

Wrong! The purpose of a thermostat is to maintain a minimum operating temperature of the engine. Your engines "cooled like a charm" because they probably never properly warmed up. A proper thermostat won't cause an engine to overheat, but a poor condition cooling system will do it all the time.

Your logic says that no car should have a thermostat in it otherwise you will suffer "slightly to radically increasing operating temp". You might want to think that through again.

 

[Hamish Racing]

Yes something like that. It’s not critical.
The “modern” thermostat should have a small ( 2mm ?) air bleed hole in it

Is the air bleed hole abouut3/8"?

 

[bobhustead]

Neil, neither I nor my logic say that no car should have a thermostat. If your car does not run too hot with the thermostat in place, by all means leave it there. As I have said in numerous other posts on this forum, if something works, don't tinker. Restriction in coolant flow restricts the volume of water that goes thru the radiator which reduces the volume of coolant per unit of time that is exposed to the air passing thru the radiator. Physics will not allow it to be otherwise. If your system is efficient enough to shed enough heat with this flow reduction, the flow reduction does not matter. An engine running at 160 degrees with a thermostat and one that runs at 160 without one are both doing exactly the same thing with regard to heat transfer.
Bob

 

[bobhustead]

When I was a BMC line mechanic in Miami, every MGB that had air conditioning ran too hot in conditions that tend to raise temperatures, like stop and go traffic. The factory recommend fix was to remove the thermostat. It worked. The factory recommended installing a blanking sleeve for the reasons related to bypass. Then blanking sleeves became unavailable for a time, so we just took the thermostats out without substituting a blanking sleeve. The cooling systems performed well without them, so we stopped using them altogether. To borrow a thought from Tom Paxton 'enough theory; now we turn to the practice of this weapon'.
Bob

 

[CJD]

FWIW

I still remember a car and driver test in the 1970's, during the gas crisis. They tested Vegas, running with no thermostat, and then several thermostats from 160 degrees through 195 degrees. The result was no change in fuel economy, but less engine wear at the higher temps. I think modern cars have taken this into account, as they all run right at the limit of the coolant...often 220 to 230 degrees F. Many are now so close to boiling over that they electrically open the thermostats if you floor the throttle, to get a jump on the cooling and prevent boil over. I assume it is worth running this close to the edge for the efficiency and reduced wear.

And...Happy New Year to all!

 

[TR Tom]

Experimented with various ways of blocking the bypass over the years and finally decided to just cap it off entirely and eliminate the bypass hose altogether. An added benefit was one less hose to potentially leak.

In addition I made two other modifications. First was to drill a small hole in the thermostat. As stated in previous posts some flow is important for proper stat function. The other mod was to remove the heater control valve. The coolant flow in the rear half of the engine is a dead end normally and I believe doing this performs the bypass function, but also evens out head temps both during warm up and when driving at full operation temps.

These changes have worked well for me, wondering what others think.
Tom