Alternative Hi-Flow T-stats for the 2LTE? 3RZFE maybe? (1 Viewer)

[John in Utah]

Ya I should have fixed that dead zone when I put the new stock gauge in when I first got the truck, I’ll probably do it if I have my dash apart again.

speaking of flow to the back cylinders, a post I was reading awhile back got me thinking about the gasket:

Are all the L head gaskets like this, where the coolant passages are obviously restricted? Has anyone tried drilling out those holes to match the ports in the block and head? I’m racking my brain to think of any reason that restriction would be designed into the gasket.

EDIT: here’s an article from felpro addressing the matter.

Do Size and Position of Coolant Holes on Head Gaskets affect overheating?

Get inside the design of a Fel-Pro head gasket and find out why the sizing of the holes matters!

www.felpro.com

They’re calling them metering holes, saying “If the holes are properly placed, but too large, the coolant can pass through the engine too quickly and fail to absorb enough heat, also resulting in overheating” - Its been awhile since I sat in a heat transfer lecture but I don’t buy that.

 

[GTSSportCoupe]

Is there a water port anywhere on the head in the rear that's blocked off?

Cummins 6bt's suffer from the same rear cylinder heat issue and to solve this in my current engine swap, and a family members dodge, I moved the heater inlet hose to the rear-most head water port. I just took the plug out of it and installed a brass nipple for the hose, and put the plug up front where it no longer needed to come from.

that would certainly help move some hot water out of the rear of the engine, and may assist with cooler overall temps? Might even make the heater work better!

Hmmm....that is a pretty interesting idea. Here is a picture of my engine when I last had it out. The lower frost plug closes the coolant passages I'm pretty sure. Not sure if something could be pressed in there with a fitting on it?

 

[GTSSportCoupe]

Ya I should have fixed that dead zone when I put the new stock gauge in when I first got the truck, I’ll probably do it if I have my dash apart again.

speaking of flow to the back cylinders, a post I was reading awhile back got me thinking about the gasket:

Are all the L head gaskets like this, where the coolant passages are obviously restricted? Has anyone tried drilling out those holes to match the ports in the block and head? I’m racking my brain to think of any reason that restriction would be designed into the gasket.

EDIT: here’s an article from felpro addressing the matter.

Do Size and Position of Coolant Holes on Head Gaskets affect overheating?

Get inside the design of a Fel-Pro head gasket and find out why the sizing of the holes matters!

www.felpro.com

They’re calling them metering holes, saying “If the holes are properly placed, but too large, the coolant can pass through the engine too quickly and fail to absorb enough heat, also resulting in overheating” - Its been awhile since I sat in a heat transfer lecture but I don’t buy that.

I'd be reluctant to drill those holes out much larger. Reason being the coolant will take the path of least resistance. If the holes are too big, the coolant won't travel to the back of the motor at all!

 

[John in Utah]

I'd be reluctant to drill those holes out much larger. Reason being the coolant will take the path of least resistance. If the holes are too big, the coolant won't travel to the back of the motor at all!

Not sure I agree. The system is under pressure, and resistance is relative. All the holes are the same size now and they would be the same size after enlarging them.

somebody needs to 3D image a head into a CAD model and we can run a thermal analysis on it and be done guessing

 

[GTSSportCoupe]

Not sure I agree. The system is under pressure, and resistance is relative. All the holes are the same size now and they would be the same size after enlarging them.

somebody needs to 3D image a head into a CAD model and we can run a thermal analysis on it and be done guessing

You know what I have noticed for the first time looking at your picture, is that Toyota has completely blocked off the coolant passage closest to the pre-cups!! WTF is with that??? No wonder it gets hot and cracks there.... If anything I think I'd drill those out to get some flow happening there!!

 

[mattimooseprime]

Hmmm....that is a pretty interesting idea. Here is a picture of my engine when I last had it out. The lower frost plug closes the coolant passages I'm pretty sure. Not sure if something could be pressed in there with a fitting on it?

That is an option - yes. a very common mod to a 12 valve cummins is a "fleece performance coolant bypass" and it uses the rear freezeplug port and adds a line there by removing the plug and bolting a secondary thermostat housing in it's place. The thermostat is overkill IMO, as the 24 valve cummins have a freezeplug with a water outlet installed there with no thermostat to fix the heat issue.

after some googling I don't see any thread in water ports anywhere back there on the 2lte. If I had the 2l out, i'd consider machining a new plug with a nipple on it and give it a go.

I don't have a picture of it right now, but I replaced the shiny sensor there with a water outlet (and then painted everything lol) . you can also see the rear freezeplug i was talking about as well. Very similar positioning and though process, it would probably do good!

 

[GTSSportCoupe]

That is an option - yes. a very common mod to a 12 valve cummins is a "fleece performance coolant bypass" and it uses the rear freezeplug port and adds a line there by removing the plug and bolting a secondary thermostat housing in it's place. The thermostat is overkill IMO, as the 24 valve cummins have a freezeplug with a water outlet installed there with no thermostat to fix the heat issue.

after some googling I don't see any thread in water ports anywhere back there on the 2lte. If I had the 2l out, i'd consider machining a new plug with a nipple on it and give it a go.

I don't have a picture of it right now, but I replaced the shiny sensor there with a water outlet (and then painted everything lol) . you can also see the rear freezeplug i was talking about as well. Very similar positioning and though process, it would probably do good!

Thanks very much for the info! Maybe something like this could work for the 2LTE. Only down side is the motor would have to come out for install...or at the very least move it forward.

 

[mattimooseprime]

That would definitely work! yeah....removing or sliding the engine forward is the bad part lol.

 

[John in Utah]

I’m not sure pulling the inner seal is going to make sense. I tried to tear into one and it looks like the metal portion is just coated in a hard rubber - a pain to get off and I’m not sure you’d gain any flow. This is the Taiho 3rz stat

I’m going to run my torture test drive up to park city with the 88 deg tridon I have installed and then again with the 82 deg 3rz one to get some temperature comparisons to go with what @GTSSportCoupe posted.

I also pulled photos of the most recent 3L (98+) and 2LT (97+) head gasket part numbers. Looks like all the ports are still either blocked or restricted. Hard to say if the drilling those out would be a benefit without knowing all the ins and outs of the coolant passages in the head. I think I saw a thread on another forum of someone doing that so I’ll try to dig it up.

 

[GTSSportCoupe]

Well I towed this weekend going camping with my family - truck and trailer loaded heavy. 3RZ t-stat and the new 4-core rad (differences since last year) I also advanced my timing a touch as I read in the manual that retarded timing can cause heat problems. (There is rumour these motors are a bit retarded to reduce NOx emissions (for Japan market vehicles)). In addition I removed the inner rubber fender shields to allow more air flow out of the engine bay from the fan. Truck ran incredible; it's never run this good. I hit 2/3 on temp gauge maximum on the worst hill. I think thats around 95-100C or so. Held around 1/4 to 1/3 on the factory gauge the entire rest of the trip. I'm really pleased.

 

[John in Utah]

Well I towed this weekend going camping with my family - truck and trailer loaded heavy. 3RZ t-stat and the new 4-core rad (differences since last year) I also advanced my timing a touch as I read in the manual that retarded timing can cause heat problems. (There is rumour these motors are a bit retarded to reduce NOx emissions (for Japan market vehicles)). In addition I removed the inner rubber fender shields to allow more air flow out of the engine bay from the fan. Truck ran incredible; it's never run this good. I hit 2/3 on temp gauge maximum on the worst hill. I think thats around 95-100C or so. Held around 1/4 to 1/3 on the factory gauge the entire rest of the trip. I'm really pleased.

that’s awesome, you’re certainly giving me hope. I ran parleys canyon twice today with my tridon still installed - once with my front bumper totally removed and now I’m convinced I have an air flow problem. I managed to hit 110 at my thermostat housing measured with an IR gun at the top of my hill. Without the bumper that was less than 93(!) I think I will run the test again with the 3rz tstat then start to Swiss cheese my bumper and remove those fender guards.

Not sure I understand why retarding the timing would increase heat? NOx emissions are generated from high combustion temps so the very idea of reducing those emissions is reducing heat. I have heard folks complain of higher egt readings but this can be explained by the delay in fuel burn caused by later timing, so more heat is being expelled as exhaust rather than doing work on the piston. But maybe your ecu has some hand in it increases fuel or something to add heat?

 

[GTSSportCoupe]

that’s awesome, you’re certainly giving me hope. I ran parleys canyon twice today with my tridon still installed - once with my front bumper totally removed and now I’m convinced I have an air flow problem. I managed to hit 110 at my thermostat housing measured with an IR gun at the top of my hill. Without the bumper that was less than 93(!) I think I will run the test again with the 3rz tstat then start to Swiss cheese my bumper and remove those fender guards.

Not sure I understand why retarding the timing would increase heat? NOx emissions are generated from high combustion temps so the very idea of reducing those emissions is reducing heat. I have heard folks complain of higher egt readings but this can be explained by the delay in fuel burn caused by later timing, so more heat is being expelled as exhaust rather than doing work on the piston. But maybe your ecu has some hand in it increases fuel or something to add heat?

Hey John, that's great news your truck stayed so much cooler without the bumper. At least you know what to focus on now. Glad to hear!

I have not stopped to think about the details of emissions/timing/heat. All I know is the 2LT/3L manual says retarded injection timing can be a cause of overheating. It's really easy to install a potentiometer on the 2LTE to adjust base injection timing, so I thought I'd play around with it. It may have no relation to how good my truck ran on this trip; it's just one of a couple things I did before I left....

 

[John in Utah]

Hey John, that's great news your truck stayed so much cooler without the bumper. At least you know what to focus on now. Glad to hear!

I have not stopped to think about the details of emissions/timing/heat. All I know is the 2LT/3L manual says retarded injection timing can be a cause of overheating. It's really easy to install a potentiometer on the 2LTE to adjust base injection timing, so I thought I'd play around with it. It may have no relation to how good my truck ran on this trip; it's just one of a couple things I did before I left....

Oh for sure, just trying understand the manual instructions - seems odd. I bought the SST to check timing just need to get a dial indicator that will fit it, I imagine mine has retarded over the KMs


So the 2LTE housing will accept a 56mm thermostat without grinding but the 3L is smaller and you need to grind it down to stock size. Weird. Also the nubs inside the 2LTE housing have been smoothed for the 3L, I still need to test that modification

Just waiting for the right size drill bit and I will try to remove some material and expand the range of the 3rz thermostat.

 

[GTSSportCoupe]

Oh for sure, just trying understand the manual instructions - seems odd. I bought the SST to check timing just need to get a dial indicator that will fit it, I imagine mine has retarded over the KMs


So the 2LTE housing will accept a 56mm thermostat without grinding but the 3L is smaller and you need to grind it down to stock size. Weird. Also the nubs inside the 2LTE housing have been smoothed for the 3L, I still need to test that modification


Just waiting for the right size drill bit and I will try to remove some material and expand the range of the 3rz thermostat.

Thats quite interesting about the t-stat housing differences.

A friend of mine had a couple old t-stats kicking around the gave me to look at. One is from a 1HDT and the other from a small block chev v8 (350). I measured the opening diameter of both (per your style earlier in this thread), and they were only 30-31mm. Those engines must create as much heat as a 2LTE under load...., and probably have larger water pumps. So I'm really thinking the opening size of the t-stat is not really the problem here. I think other parameters of these t-stats are more important - such as how fast they open, what temp they open, and how well made they are.

Now you may certainly be onto something with the headgasket holes. If I had the time I'd be tempted to slightly open up the holes at the back of the head to increase flow to the hotter cylinders (better balance flow), and increase the coolant flowing from back to front of the cylinder head a bit more. I think the motor would benefit from this.

Anyhow, I think the ideal pop-in t-stat for these motors might just be the OEM 82C 2LTE one. Part number 16340-54040 . That said, my larger 3RZFE one is working damn fine, so I'm just going to stick with it for now. Only problem is the motor may have lost some efficiency running cooler. May pop in a warmer t-stat once the camping/towing season is over and winter arrives.




EDIT: Dec 8, 2020 - I've gone back to the OEM 88C 2LTE t-stat the last few months. My modification to the 3RZFE t-stat meant it took a long time for the motor to warm up (didn't seal well when closed). Ultimately, I don't think the 3RZFE t-stat helped my truck significantly while towing. I bought a brand new 88C and 82C 2LTE t-stats at the end of summer, and swapped in the warmer one to help keep the truck efficient with fast warm up in Fall/Winter. May swap back to the 82C one for towing next summer.

So 88C part number I'm running now is: 90916-03099

82C part number I also bought is: 16340-54040

 

[John in Utah]

I think I figured out the numbs on the 2lte housing are to force orientation of the air bleed valve to be high, since the housing oriented the thermostat on its side.

I’m going on a longer trip this weekend and it should be a hot one out here so I’ll give my 3rzfe unit a good test. They’re so easy to change it’s almost like switching to a summer weight oil

I did order in a spare 3L housing so there’s still some testing to be done...

 

[bjowett]

You are running Evans Coolant?

 

[John in Utah]

You are running Evans Coolant?

Sorry for the late response. I ran Evans when I bought the truck but have since switched to Toyota red conventional. @GTSSportCoupe and many others here run Evans.