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And I still ride my 1988 and 2001 CR500. Bought them both brand new from the local honda dealer!!!!

What the heck does this have to do with what people are talking about????????
'Cause who doesn't want to talk bikes??? :) KTM EXC and Vstrom here...

Very interesting findings CR500. Those are some serious restrictions. I think you're onto something here.

Also didn't know they even made "inlet thermostats". Looks like a bad idea, but there must be a reason? Did the 5.4L have a normal thermostats? Those didn't seem to have nearly the overheating issues of the Ecoboosts.

Regarding the oil cooler, there must be some kind of restriction in that plastic fitting otherwise there would be no flow thru the cooler. Water always take the past of least resistance. A wide open hose vs a cooler with a bunch of small passages, nothing would flow. Anyone care to sacrifice theirs?
 

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What the heck does this have to do with what people are talking about????????
He asked about my RZ500 not many of those bikes in the states 4 cylinder 2 stroke , like 2 Banshee motors fused together.

i'm am interested what you all come up with this thermostat housing.
 

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'Cause who doesn't want to talk bikes??? KTM EXC and Vstrom here...

Very interesting findings CR500. Those are some serious restrictions. I think you're onto something here.

Also didn't know they even made "inlet thermostats". Looks like a bad idea, but there must be a reason? Did the 5.4L have a normal thermostats? Those didn't seem to have nearly the overheating issues of the Ecoboosts.

Regarding the oil cooler, there must be some kind of restriction in that plastic fitting otherwise there would be no flow thru the cooler. Water always take the past of least resistance. A wide open hose vs a cooler with a bunch of small passages, nothing would flow. Anyone care to sacrifice theirs?
The reasoning is that it maintains a constant inlet temperature into the engine at all times.

Imagine you are cruising down the highway on a -30F day and your engine is warming up. All that coolant that’s sitting in your radiator not moving is sitting at -30F. If you have a outlet side Tstat then the engine continues to warm until it opens, when suddenly you dump all that super cold coolant into your hot engine.

An inlet side tstat keeps tabs on both the coolant coming from the radiator and from the bypass. If the Tstat starts to open when the truck warms up then that cold coolant from the radiator flows over the Tstat with the hot bypass coolant and the thermostat will read the two and modulate the ratio such that the coolant entering the water pump is very near 188F no matter what.

It’s probably a better solution for 99% of the driving people do but it’s probably not the best for extreme situations like towing.

Now that’s I’ve though about it more I understand why the ECT’s are so erratic. If the inlet temp is always the same, and you change the amount of power/heat the engine generates, the outlet has to change. If the engine is always sucking in coolant at 188F and making 250 BTU of heat, the sensor is reading 200F. If you then start climbing a mountain and the engine is making 500 btu then the coolant must heat up twice as much so the outlet temp at the sensor is now 212F. Coolant is still entering at the same temp but it’s absorbing twice as much heat.
 

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Figuring out if this is a cooling system issue or a thermostat issue should be easy. Put a thermocouple in the cold side coolant tube from radiator just before the thermostat and then go tow a trailer up a mountain.

If the coolant leaving the radiator is hotter than the Tstat temp then that means the radiator is not big enough to cool the engine effectively and the coolant entering the engine is too hot.

If the flow coming from the radiator is much cooler than the Tstat temp then the Tstat would be the weak link. It’s slowing flow through the radiator enough that the coolant can cool substantially under high load.
 

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The reasoning is that it maintains a constant inlet temperature into the engine at all times.

Imagine you are cruising down the highway on a -30F day and your engine is warming up. All that coolant that’s sitting in your radiator not moving is sitting at -30F. If you have a outlet side Tstat then the engine continues to warm until it opens, when suddenly you dump all that super cold coolant into your hot engine.

An inlet side tstat keeps tabs on both the coolant coming from the radiator and from the bypass. If the Tstat starts to open when the truck warms up then that cold coolant from the radiator flows over the Tstat with the hot bypass coolant and the thermostat will read the two and modulate the ratio such that the coolant entering the water pump is very near 188F no matter what.

It’s probably a better solution for 99% of the driving people do but it’s probably not the best for extreme situations like towing.

Now that’s I’ve though about it more I understand why the ECT’s are so erratic. If the inlet temp is always the same, and you change the amount of power/heat the engine generates, the outlet has to change. If the engine is always sucking in coolant at 188F and making 250 BTU of heat, the sensor is reading 200F. If you then start climbing a mountain and the engine is making 500 btu then the coolant must heat up twice as much so the outlet temp at the sensor is now 212F. Coolant is still entering at the same temp but it’s absorbing twice as much heat.
The old school outlet thermostat usually had a small hole or bypass in it so that the radiator coolant doesn't just sit there. It warms up, just not as fast as the engine because it's restricted by the closed thermostat. Once the stat opens and full flow is allowed, the coolant is no longer super cool. It's colder, yes, but not so extreme.
 

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That's pretty disheartening to hear that the thermostat is so restrictive. To add to the questions, doesn't anyone think that having this flow more is going to crack the block or something given the amount of heat at the back of the block from the turbos? Seems like they want them to run hot to get better emissions, not better performance. But recirculating a lot of the heat instead of removing it would help keep things more stable in regard to temperature extremes, yes/no?
no crack block. if anything here will ever break, its the plastic return manifold.
there would still be a thermostat, which is still a restriction. when any thermostat opens, its not like at set temp it goes wide open, its usually over a 10-15 degree range. and most also if drop below set temp immediately start to close.
on the note of the stock thermostat not opening much, im not sure, but would be willing to bet an aftermarket one, regardless of temp probably would move the normal amount.

mass, about your bypasss question, I would assume there is always some sort of differential pressure in the system, but not nessacarily how/ where youd want to see. it still has the heater return to pull hot coolant from, I bet that is used to control tstat more than the bypass.

454, yeah the aluminum intake 3.5 motors have slightly smaller tstats.
I really think I/ we lucked out on this early 7.3 one. I dug around a little since, and really cant find much that will work easier than this one. even the center port, the part that moves, is basically same size as the stock one.

might try and start on the return manifold here in a day or so.
a
i'll say it again. that rz is so badasss. man youre lucky!!!! I got to race the Suzuki version once, rg500, at the track in college station, I wish I had it on film. just for the noise part. ive always been a 2 stroke guy. street wise I owned a slew of rds, 350/400s, a slick rz350, a bunch of h1 triples, a smaller one, and a h2/750. I still even have a banshee, but with a powervalve rz top end.
an old buddy has my old h2. just been sitting for 15 years. im in process of slowly getting it back. my neighbors/ wife will probably hate me.
ford4hot, that's a cool vmax. I owned about 3 of those outa high school. stop to stop light I could eat anything. and usually do it laying rubber whole time. my last one I did a chain drive setup on it. wish I had another one of those. such a cool bike, and about the best sounding 4 stroke.

towm8r, that's awesome. I got pretty crazy with the big cr, at one time I think I owned 30 500 2 strokes, 20 of them cr500s. im down to probably 6-7 complete, but have enough parts to build maybe that many more.
I see one here/ there, but still rare to see one in original chassis. I hope to get my 84 finished by Christmas, want to use that for vintage stuff.
 

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The reasoning is that it maintains a constant inlet temperature into the engine at all times.

Imagine you are cruising down the highway on a -30F day and your engine is warming up. All that coolant that’s sitting in your radiator not moving is sitting at -30F. If you have a outlet side Tstat then the engine continues to warm until it opens, when suddenly you dump all that super cold coolant into your hot engine.

An inlet side tstat keeps tabs on both the coolant coming from the radiator and from the bypass. If the Tstat starts to open when the truck warms up then that cold coolant from the radiator flows over the Tstat with the hot bypass coolant and the thermostat will read the two and modulate the ratio such that the coolant entering the water pump is very near 188F no matter what.

It’s probably a better solution for 99% of the driving people do but it’s probably not the best for extreme situations like towing.

Now that’s I’ve though about it more I understand why the ECT’s are so erratic. If the inlet temp is always the same, and you change the amount of power/heat the engine generates, the outlet has to change. If the engine is always sucking in coolant at 188F and making 250 BTU of heat, the sensor is reading 200F. If you then start climbing a mountain and the engine is making 500 btu then the coolant must heat up twice as much so the outlet temp at the sensor is now 212F. Coolant is still entering at the same temp but it’s absorbing twice as much heat.
its like the motor has air pockets everywhere, maybe it does not but kinda appears that way.

on the dumping cold water thing, its not an immediate deal like that. at set temp most tstats barely crack open. usually 10-15 degrees later its full open. and not until that point is the bypass shut off. that's the other nice part about the shutoff/ bypass part.
if you eve had a normal system with bypass port, and a mechanical temp guage, on most usually temp will go slightly higher than tstat set point, then back down to around it, then from there depending on situation stay or heat up slightly.
Ive built a lot of massive radiators/ cooling system stuff for vehicles over the years. now I don't live in the cold, but even in the cold we sometimes get (teens) I don't see anything different temp wise, rapid dropping, etc than I would on same vehicle than in the heat. just usually in cold if idle long it will close tstat. normal stuff like that.
again, if im in way left field, I can just bolt it all back up the stock way. no harm done. idealy though id prefer to build a new return manifold, that mounts this tstat housing right there. then just run a long return hose maybe over p-side valve cover or something. I don't like that molded plastic mess. but first see if this will even work worth a flip.
 

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The old school outlet thermostat usually had a small hole or bypass in it so that the radiator coolant doesn't just sit there. It warms up, just not as fast as the engine because it's restricted by the closed thermostat. Once the stat opens and full flow is allowed, the coolant is no longer super cool. It's colder, yes, but not so extreme.
My jeep certainly doesn't have this feature and Im sure its to get the engine up to temp as quickly as possible. Its an outlet side tstat with no hole and a spring loaded bypass plate. When I had put in an inline thermostat in the hot side radiator hose because my stock thermostat had failed, I did drill a 1/16" hole to allow a small amount of coolant to pass, but that was so that the thermostat would not be slow to respond since it was not in the direct flow coming out of the head.

its like the motor has air pockets everywhere, maybe it does not but kinda appears that way.

on the dumping cold water thing, its not an immediate deal like that. at set temp most tstats barely crack open. usually 10-15 degrees later its full open. and not until that point is the bypass shut off. that's the other nice part about the shutoff/ bypass part.
if you eve had a normal system with bypass port, and a mechanical temp guage, on most usually temp will go slightly higher than tstat set point, then back down to around it, then from there depending on situation stay or heat up slightly.
Ive built a lot of massive radiators/ cooling system stuff for vehicles over the years. now I don't live in the cold, but even in the cold we sometimes get (teens) I don't see anything different temp wise, rapid dropping, etc than I would on same vehicle than in the heat. just usually in cold if idle long it will close tstat. normal stuff like that.
again, if im in way left field, I can just bolt it all back up the stock way. no harm done. idealy though id prefer to build a new return manifold, that mounts this tstat housing right there. then just run a long return hose maybe over p-side valve cover or something. I don't like that molded plastic mess. but first see if this will even work worth a flip.
I get that it doesnt open instantly but it can happen rather quickly especially in the right scenario. Here in Utah I am very frequently climbing big grades. If I happen to climb one of these grades right as the engine is reaching the t-stat temp then it will open very quickly since the engine is under heavy load and I can actually see the ECT drop by 5°C within a second or two. If I am just cruising on a flat road then it will nice and slowly climb up to the tstat temp and sit there without any drama.

You are right though, the Ecoboost does act like there are air bubbles. I think your solution will provide a far more consistent coolant temp. I would still be curious to see what temperature the coolant leaving the radiator is at when towing as I think that would tell us a lot about the performance of the system. It would at least be able to rule out whether our thermostat or waterpumps are an issue.
 

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You are right though, the Ecoboost does act like there are air bubbles. I think your solution will provide a far more consistent coolant temp. I would still be curious to see what temperature the coolant leaving the radiator is at when towing as I think that would tell us a lot about the performance of the system. It would at least be able to rule out whether our thermostat or waterpumps are an issue.

Would this be as easy as using duct tape to adhere a temperature probe to the upper radiator hose? Or does the probe need to be "in" the coolant itself?
 

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Would this be as easy as using duct tape to adhere a temperature probe to the upper radiator hose? Or does the probe need to be "in" the coolant itself?
Rubber is a poor conductor of heat, so a hose isn't a good idea. Attaching directly to a piece of metal and wrapping the sensor in insulating tape should work, we do it in refrigeration systems all the time. Maybe on the Tstat housing just before the stat. Just would have to make sure the insulation tape could handle the temp. You won't see full engine temp coming back from the radiator, but it could be upwards of 200F and I don't know many tapes that can handle that much.
 

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Okay. So something like this is better, cut into the top radiator hose?
https://www.summitracing.com/parts/mio-mmwhs-38-bk

Would be nice to not have to buy a gauge, but I don't know of any way to feed this through OBD port for torque or some other monitoring system.
 

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That would work, but if you just need a 1/8npt port, theres’ enough meat on the return manifold thing to likely tap a hole somewhere on it. If you have something like a edge or sct device, you can buy temp probes that they can easily read.
On a side note, i rounded up a typical replacement tstat today for this. Found a 180 degree motorad. I noticed on it the bypass, although in cold position it closes off port just like the stock one, but what its connected to does move when tstat opens, unlike the stock one. The tube that holds the flange on is just flared out on end to keep everything in there. Was going to cook this one up, and measure its full travel length. my idea is to simply cut the center tube back, and reflare end to move disc up. That way it will function as a normal bypass. It will allow water to pull thru when closed, and when open shut off the port, like a normal bypass would. That would be easier to do then machining a collar to raise the port height to match the diesel thermostat i found. And who knows, but im sure itd help anyway. You know, using the stock location.
 

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So i checked out the motorad stat. It works as id expect. Opens about 10-12mm.
03535FBF-D521-48C7-B1D5-8C17A0356565.jpeg

40931F67-D3BF-49FF-AB24-F914B4EC67C3.jpeg

BA4FDD9B-7EAD-45EA-9C37-3717AB7FA177.jpeg

so if i make the installed cold length around 32mm, instrad of 40, that will make this bypass function as normal, and give a hair of spring pressure against disc when tstat fully open.
Here is roughly where the disc needs to be when cold.
68B6E0CE-6D18-4820-88DB-23B3184BC59D.jpeg 16BDA493-BD24-41AC-B749-52A3C4BA7495.jpeg

need to cut down tube, reflare end. Will give it a go tomorrow
 

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Okay. So something like this is better, cut into the top radiator hose?
https://www.summitracing.com/parts/mio-mmwhs-38-bk

Would be nice to not have to buy a gauge, but I don't know of any way to feed this through OBD port for torque or some other monitoring system.
I actually have one of these sitting in my garage and this just reminded me. My dad bought it for something and never used it. so he gave it to me. I am pretty sure its a 38mm/1.5" too. Is that the size of the lower hose? Does the lower hose have a coil in it to keep it from collapsing under suction from the pump?

I also just happen to have a 1/8th NPT temp sensor and Glow shift gauge that I was planning on installing on my jeeps intercooler. Hmmmm.

How much of a PITA is it to drain the coolant on these?
 

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I found this thermostat long time ago for my lightning , murray ultra stat supposed to have 50 % more flow . i will try and measure it this weekend diameter looks same but overall length is shorter.


from website

Murray(R) Ultra Thermostats
  • Triple-bridge design increases strength, stability and durability
  • Wider opening allows up to 50% more coolant flow
  • Added bypass valve allows a small amount of coolant to circulate before fully opening
  • Allows trapped air in the cooling system to escape
  • Reduced delay in engine warm-up


Cr500 , yeah the RZ 500 sounds pretty insane at full tilt . Mine is fully registered in AZ to ride on street. I'm rebuilding a 2nd set of carbs for it now in my spare time. original ones started getting gummed up a little from sitting. Parts are very expensive luckily i've been able to find small parts here and there , bought mirrors from a guy in Singapore and have a speedo in MPH from England new in the box.
 

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If thats a old modular thermostat, then the flange is like 3/8” too small i think. I remember all the modular ford thermostats being around 50ish mm flange. This 3.5 is 61.
 

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Y'all boys who dive into your trucks' engines like this inspires me! If I were younger, better health, I'd be in to my elbows too...all I've done so far is added an oil catch can right after I got mine. Towing my 6,000 pound travel trailer has been no heat problems so far. I hate when a truck runs hot like my Chevy did! The old 350 would get hot not towing.
 
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