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

[GTSSportCoupe]

On my never ending quest to continue improving the L series.....

I really think one of the faults with this motor is the pathetic tiny t-stat. It simply doesn't let the coolant flow fast enough to the rad when the motor is under high load. This allows the heat to build in the head (pre-cups shedding heat into coolant), while the rad is still relatively cool. I've seen this first hand when using a FLIR thermal camera during some of my testing. It was clear the heat could not get from the motor to the radiator fast enough.

I'm running an 82C Tridon Hi-Flow t-stat currently. I'm running a 1HDT fan, a modified fan hub (new oil and lower turn on temp). My rad has been re-cored to 2.5" thick (four core). So my cooling package should easily be enough for a little 2.4 motor. IF THE HEAT can get to it!

Compare the L series T-stat to a 3B one sometime...huge difference. Yet the motors make the same power (stock). Now I did find the Tridon Hi-Flow made quite a perceptible difference, but I think we can do better. It would also be nice to find one that is for a North America motor to save on shipping from OZ.

So here are some dimensions to think about.

Here is a 2LTE T-Stat (ironically it's the same dimensions as a 1980's 1.6l gas corolla T-stat!!)

Here is an early 3RZFE (or maybe 2RZFE?) T-Stat:

Here is a later 3RZFE T-Stat:

They all will physically fit in the t-stat housing (just have to move the gasket under instead of around it), but there are a range of differences in the opening diameter. Some are too large (the only one I tried a few years ago), and it could not even open properly as it jammed inside the housing.

Maybe I'll try to find some time and a patient parts guy who'll grab a bunch of 3RZFE t-stats off the shelf for me. I'll try to find the best flowing one that will still open in the limited housing size. I'm confident there is a particular brand/ part number that will be the ideal one.

A local shop that used to work on these trucks in BC (ATEB) swore by this sort of modification as the fix to the engines. They actually had an adapter they fitted that allowed use of a 1KZTE thermostat. I have a picture somewhere....

 

[GTSSportCoupe]

@Jarrat @Postoy @Nas90tdi What do you guys think?

 

[GTSSportCoupe]

I've also thought about making a whole new billet t-stat housing from scratch. Designed to accommodate an appropriate sized t-stat that could never fit in the OEM housing. Like one from one of the larger diesels, or a 6 cylinder gasser. I don't think anyone has ever tried this... Might be 'the fix' for these motors, haha.

 

[GTSSportCoupe]

I like responding to my own thread...LOL.

Here are some pictures of the 3RZFE t-stat from Toyota. Looks like a good candidate. Although I wonder if it opens more at a given temperature (in addition to the larger diameter). Would have to heat it up and observe I suppose. It might need a custom spacer.

I wish I could buy from my local Toyota stealership without providing a bloody VIN...

 

[Nas90tdi]

I agree flow rate is a big factor in how the engine cools. My testing thus far has agreed with yours. After switching to the high flow Tridon my temp drop at opening was much more dramatic. And, because of the digital gauge I use my response time is very short, so it is extremely obvious when the tstat opens.
My drop ,if I am at lets say 190F, is about 14 degrees F when the tstat opens all the way. So, using that simple logic the radiator is capable of more because that drop is seen even after the water runs completely through the engine. That makes me think I would like to see the water temp at radiator exit before it cycles through the engine back to the sensor at the t-stat port. That would give you an idea of the temp drop capable for the radiator once it fills with hot water again.

 

[GTSSportCoupe]

I agree flow rate is a big factor in how the engine cools. My testing thus far has agreed with yours. After switching to the high flow Tridon my temp drop at opening was much more dramatic. And, because of the digital gauge I use my response time is very short, so it is extremely obvious when the tstat opens.
My drop ,if I am at lets say 190F, is about 14 degrees F when the tstat opens all the way. So, using that simple logic the radiator is capable of more because that drop is seen even after the water runs completely through the engine. That makes me think I would like to see the water temp at radiator exit before it cycles through the engine back to the sensor at the t-stat port. That would give you an idea of the temp drop capable for the radiator once it fills with hot water again.

I've wanted to measure the coolant temp exiting the radiator too; that would be a great test.

When I used the FLIR camera, I could tell the coolant flow was so little it wasn't even flowing through the whole rad. Only the 1/3 or 1/2 closest to the inlet/outlet showed warm. And by the bottom of the rad, even that was cold already.

I wonder if an over-drive pulley on the water pump would be beneficial also? Wouldn't want cavitation, but more flow would be nice....

 

[Postoy]

I think you are on the right track

If you wanted to go the route of custom housing, I have a spare housing that we could model up to fit a larger t-stat. Then I’m sure @Jarrat could machine.

 

[GTSSportCoupe]

I think you are on the right track

If you wanted to go the route of custom housing, I have a spare housing that we could model up to fit a larger t-stat. Then I’m sure @Jarrat could machine.

Hey Postoy, thanks for the offer of spare housing. I asked a local friend who parted a Prado a while back and he thinks he still has one too; but will let you know. It would be a handful to machine one from billet due to the bypass design, sensors, rad cap etc. Would the ultimate solution though! If they made the difference I'm sure a person could sell a lot of 'em if they wanted. There are a lot of 2LT/2LTE/3L/5L still on the road out there.

 

[John in Utah]

I might have a 3rzfe thermostat in the shed from my old 4Runner build, I’ll take a look and compare with the stock 2lte one I have.

You can test your hypothesis pretty easy by simply pulling the stat all together and comparing the temps

 

[GTSSportCoupe]

I might have a 3rzfe thermostat in the shed from my old 4Runner build, I’ll take a look and compare with the stock 2lte one I have.

You can test your hypothesis pretty easy by simply pulling the stat all together and comparing the temps

Right on man, I look forward to what you have to say about the two. Can pop 'em in a pot of hot water and see the differences when they open too.

Pulling the t-stat doesn't work that well as it leaves the bypass open too. This means much of the coolant will just go straight back into the engine without even going to the radiator. I wish it were so easy.

 

[John in Utah]

Well no luck, must have thrown it out with the 3rz I wrecked But now I’m interested so I’ll put in an order for some 3rz units. correct my part numbers if they’re wrong:

90916-03099 - 2LTE/3L
16340-54010 - 5L/5LE
90916-03101 - 3rz pre 97
90916-03120 - 3rz 97+

I have a 03099 still in the box, so I’ll buy the other 3 and do some testing. There’s a tridon in my truck now, so I’ll use the oem stat as a control and a spare 2lte water housing I have to check clearances.

I did compare side by side with the Tridon when I bought it, and did find the Tridon opened faster and had a slightly larger diameter. I’ll replicate this with the new ones I get in.

 

[GTSSportCoupe]

Right on! Thanks for the R&D help! And thanks for those pictures with measurements too. I was kicking myself for not having taken pictures too. I did a big parts purge a while ago and threw all my old t-stats away.

Your part numbers look good to me; that'll definitely give you a good selection to work with. They cross to a lot of different models and engine variations.

 

[John in Utah]

Sure thing. This thread came at a good time, I just put an aluminum ebay radiator in and noticed a lot of the same things talked about above. It got me thinking the limiting variable might not be the capacity of the rad like I always thought (the Hilux/surf rad is comically small).

Give me a week or two to collect parts and I’ll post back here with some results.

 

[Nas90tdi]

That's what I got to thinking as well after watching the temp differential after I swapped to a digital gauge. We all assume the radiator is the too small or not efficient enough. Myself included. But, I kept watching the drastic temp drop and it made me realize that would be impossible if the radiator was not sufficiently capable of cooling the water in it. If it was, you would see diminishing returns as it heat soaked. But, I haven't really noticed that exactly.
And, honestly if anyone would see those diminishing returns it would be Nick because he tows with his. The water would get hotter and hotter as the radiator lost it's ability to shed the heat. But, my drop when the t-stat opened was enough to make me start watching it more.
Nick, this is one of the more interesting tangents you have went off on since you have had so much free time.

 

[GTSSportCoupe]

I stopped by NAPA and Lordco this morning as I had a couple spare minutes. The Lordco 3RZFE t-stat was the huge opening diameter one I'd bought before that is simply too large for the housing when it tries to open (coolant can't even get around the 'door'). The NAPA one was smaller, but just a bit bigger than the Tridon hi-flow. Using the same measuring technique as @John in Utah it measures 1.43". The NAPA one I bought is a 180F (82C), but they did have a much colder one too; 170F (77C) I think.

I found I had a 2LTE t-stat in my remaining parts stash that is exactly the same as the one John has in his picture above. I've dumped it and the new one into a beaker of water at work and am monitoring the temp with a thermocouple as I type. I'll monitor the opening rate and snap a few pictures when they're both open.

I'm not sure the 3RZFE one I bought will be significantly better than the Tridon. But at the very least, it's a local and cheaper option....

I think with some searching there will be a better one.... Looking forward to what you find with the ones you ordered John. Usually the OEM ones are best.

 

[GTSSportCoupe]

OK, they both open and close at about the same rate. They don't even START opening until 82C. Half open at about 85C. They're fully open by about 88C. They open about 9mm or so maximum. The distance from the t-stat main outer seal flange to the by-pass shut off is basically the same between them when they're open. About 44mm. Measures around 35mm when they're closed.

They both have rubber seals which limit the area of the opening. I'm thinking of removing the seal on the 3RZFE one, as that would expand the flow opening by a lot. The metal part of the 'door' still contacts the thermostat body, (like a Tridon), so I think it'll be fine still when closed. Or maybe I'll just return it and look for something better...LOL.

The outer diameter of the 3RZFE one is 56mm, the 2LTE one is 52mm. I think ideally 2mm should be removed (ground?) from the radius so that the t-stat can sit in the factory seal and have the correct offset in the housing (to close the bypass correctly).

Here are a couple pictures when they're open.

2LTE one:

3RZFE one:

 

[GTSSportCoupe]

Dug through some of my old pics, and found one showing a Tridon Hi-Flow 88C next to the same 82C as above.

 

[GTSSportCoupe]

Found my old (partially failed) 88C Tridon Hi-flow t-stat last night as well. Had fallen behind a bunch of junk in my shop.

I also removed the rubber from the 3RZFE t-stat and used a lathe to take it down to 52mm so it would fit properly with the 2LTE gasket.

I measured my Tridon (opening part) diameter compared to the 3RZFE, and they're actually the same. But the 3RZFE seems to open further. It's also a much tougher construction than the Tridon. I'm beginning to think the Tridon t-stats are actually a fairly cheap construction. @Nas90tdi had one fail on him too.

So here is a picture with the three t-stats fully open. Keep in mind the Tridon is pretty toast and may not be as open as it would be when new (although the picture above is from when it was new, and it doesn't seem much different!?). In this picture, the Tridon was not even opening enough to properly block off the bypass! Another major issue indeed!

Currently I have a pretty new Tridon 82C Hi-flow t-stat in my truck. I'm thinking of yanking it to install this NAPA 3RZFE one now.

3RZFE left, Tridon middle, 2LTE right.

Another thought that occurred to me, is if the opening part on these t-stats gets too large, it actually blocks flow in the housing from getting to the t-stat opening. So basically there will be an optimal maximum size where flow area around an open t-stat equals flow area through the t-stat if that makes sense. Unless we come up with a way of modifying the t-stat housing.

 

[John in Utah]

My concern Is that the boiling pot of water test doesn’t account for any physical limitations of the housing. Have you tried measuring the distance from the tstat flange to the bypass port? If it’s shorter than the full range of the stat I don’t think you’ll see it open all the way in the housing if that makes sense.

when this is all said and done I don’t imagine I’ll keep the tridon in my trucks. Didn’t realize folks had experienced some failures.

I’m all for modifying the housing though, you can still get the 3L ones new

 

[GTSSportCoupe]

My concern Is that the boiling pot of water test doesn’t account for any physical limitations of the housing. Have you tried measuring the distance from the tstat flange to the bypass port? If it’s shorter than the full range of the stat I don’t think you’ll see it open all the way in the housing if that makes sense.

when this is all said and done I don’t imagine I’ll keep the tridon in my trucks. Didn’t realize folks had experienced some failures.

I’m all for modifying the housing though, you can still get the 3L ones new

A friend of mine has a spare t-stat housing that I'll use to take some measurements; just have to pick-up once he finds it. But what I can say for now is the 3RZFE measured distance from seal flange to bypass block off was very close to the same as the 2LTE one when I measured in the pot of water with them fully open; maybe 1mm more at most. Which would mean it'll certainly block off the bypass tightly. I can't say the same for the Tridon from the looks of it.

I agree, the Tridon is no longer trustworthy for me.