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I have an 88Sunrader. OD=105kmiles. 22re. “Louise”.


I took her into a mechanic here in Southern Oregon as she was running a little warmer than I would like - on climbs nearing 3/4 but never got to 3/4. On flat roads in Summer the gauge was sitting just over half. It never overheated but just seemed to be running a little hot. So I took her in to get some work done. The radiator had a few hairline cracks in the top which I had patched with JB weld and they were holding. I figured a new radiator was in order - so this May I had the following work done: 


List One - “things having to do with the cooling system”

- new three-core all-metal radiator

- new radiator cap

-new upper radiator hose 

- new lower radiator hose

- new thermostat (JDM) - Im not sure if it was tested before he installed it - putting in a pot of water on the stove to check for opening etc. 

- fresh coolant (green)

- removed Original Air Conditioning  system (non-operational since 2015) 


List Two - “things seemingly not related to the cooling system”

- new front seal 

- new oil pump seal

- new transmission cooling lines

- reconfigured original battery system by removing the fiberglass box for carrying two batteries under the hood. Found homes for components that were attached to the double battery box. 

- changed out rear differential fluid

- drained and refilled Automatic Trans Fluid

- new fuel filter

- new power steering pulley (tensioner) bearing

- replaced alternator belt. 


With all of this finished I decided to head south to California for a week. The day I set out the forecasted high was 78 degrees. 


On my way up Siskiyou Summit (a long steep climb I had done many times before) I immediately noticed that the heat gauge was up to three quarters and was approaching the white line that comes just before the red section on the gauge. Before getting all this work done, my engines temperature had NEVER gotten to three quarters. This was strange new territory. Very peculiar. I turned on the heater and kept an eye on the gauge. It never overheated or got into the red zone but it got close. Short story, I made it down and back on this trip. Upon returning I called the mechanic and he said he thought it was a blown head gasket and he was out of ideas, wanting to send me off to another mechanic. For real? 


These high temperature gauge readings never happened before I got the above work done. 


Other pertinent information: 

- engine seems to run fine. Same amount of power as usual and it is consistent. 

- no white smoke coming out the tailpipe

- oil is oil-colored and NOT milky,frothy, etc

- I took off the radiator cap when cold, started it and ran for 15 minutes - looked for bubbles rising in the radiator - saw no bubbles. 

- fan comes on immediately 

- before starting I moved the fan with my hand - felt some resistance - hard to explain how much - did not seem overly stiff or loose. 


Suspicion List: 

 - something’s out of whack from the removal of the AC system

- What’s up with the new thermostat? 

- fan clutch problem. 


Just to beat that horse I will say again: my temperatures were FAR LOWER before I had all this work done. I find it difficult to believe that getting this work done has coincided with a failed water pump, a blown head gasket, or a faulty fan clutch - although the fan clutch could have been the original problem that was causing it to run just a little hotter than normal before I took it in. 


I read two other stories shared here with similar symptoms described and I believe both of them were fan clutch related. 


Other solutions I am considering: 

- drill some holes (two 1/8” ones) in the thermostat? - I am curious to know if anyone has experience with this

- check the level of the oil in the fan clutch and potentially add some of a higher or lower viscosity. 


Thanks for any ideas you may have. The knowledge base here is prodigious as is the depth of good will. 


Muchas Gracias. 










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thermostat is not the problem. could easily be a bad new radiator. not unheard of. fan clutch is also suspect. easier to swap out to see

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test your antifreeze. too high of a concentration can cause higher engine temps. 

actually a bad thermostat could also be a problem.  I've had that happen with a new one.

didn't open in pot of boiling water.

Linda S

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I have had a $4 thermostat with a hole drilled in my 22re camper for years without issue.  


Fan clutch issues will definitely result in spikes in temperature. In the Summer I hear my fan clutch kicking on and off while driving at all speeds.


Didn't see water pump on the list. Any coolant leaks in the area of the water pump?


Though there are currently no clear head gasket symptoms don't scoff at the idea as it is a job that will need to be done. Unresolved heating issues is a sign of a potential head gasket issue amongst other things.  Glad you didn't go red as that will quickly do a head gasket in. 

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Thank you extech, Linda S., and Scott IV. 


Extech: would an IR heat sensing gun be the tool to ascertain the health of the radiator? To check for cool spots when running?


Linda S: so mebbe dilute with water. Have you heard of this REdline water wetter?


Scott iv: no leaks at water pump. The fan seems to run constantly but never kicks into a higher/louder phase. 


Thanks again! 

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Toyota Red antifreeze and "normal" green antifreeze do not play well together. Do you know what was in your Toy? If it had green in it then never mind. If it had red you will need to flush the entire system, including the heater. Install 50% mix of antifreeze of your choice.

A simple compression check will show up a blown head gasket about 90% of the time.

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yes , ir gun is the way to check, but im with the others- fan clutch

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if the engine was hot at the time the clutch is bad.  to check another way, get a piece of cardboard and cover the radiator front. when it runs it will heat up quickly and you should hear the fan engage when it gets above normal running temp

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Fan is not the problem.


When engine is hot and then turned off— fan stops quickly. No extra turns.


Will reinstall the old thermostat tomorrow morning. 

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I have a theory now which I think might explain the situation: 


- back in 2018 while working in Montana, I noticed that Louise was running too hot so I had a new three core all-metal radiator installed. At this time the AC was still working and I was using it periodically. Some cracks appeared in the top of the radiator soon after installing it. I attempted the patch with JB weld which was never too complete. She still leaked a little. Not much. I drove on. Until I noticed the heat being too high again so I took it in this time about a month ago and got another radiator installed of the same metal 3 core variety and then I noticed even more severe heat in the engine. This was when I reached out to you all and began this thread.


Here’s what I think happened:


- the head gasket was leaking back in 2018 in Montana, causing enough pressure to build up in the system until the radiator cracked - thus letting out some of the pressure and somewhat equalizing the pressure in the system. Now, with this recent tight, uncracked radiator the head gasket is still leaking pressure into the system which no longer can leak out of the new, intact radiator, thus causing more severe heat build up. So… I am now looking for a shop to replace the head gasket. The mechanic who has been working on it does not do head gasket jobs. 


I have two questions: 


(1) does anyone have a shop to recommend for head gasket work on a Toyota motor home in Southern Oregon? Medford, Gold Hill , Grants Pass? One shop I reached out to today in Phoenix, OR quoted me an hourly rate of $170 an hour to do the work. After my shocked response they said they could do it for $150/hr. Apparently this is their fee for motor home work. As they are working on the trucks motor and not really working on the motor home-ish parts I thought this was a little much. Not sure. Be curious to hear anyone’s thoughts on this. 


(2) while the head is off for this job, are there other procedures that I should have done while Louise is in such a dis-assembled state? 


Again, deepest thanks for your thoughts and wisdoms with this ongoing situation. 

Edited by YoungSage
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I have had pretty good luck with Craigslist mechanics. Head gasket can be done in a driveway. Do you have somewhere they could work?

I see a few in your area and one of them is ASE certified. Good mechanic and a decent machine shop to resurface the head and good quality gaskets. Worth investigating. 

Linda S

Ask if you can talk to some of their customers. If they are good, they have repeat customers

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unless your radiator cap is bad, pressure will never get over the cap rating. not cracking radiator

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3 hours ago, Scott iv said:

You could test your theory by purchasing a combustion leak detector to detect the presence of exhaust gas in the coolant. 

A compression check will tell you a lot too.

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Always a late comer to the party here.

Summer's coming and the annual heating issues with it.  I always wait for the old-timers to report back on problem solving and listen-up, it hasn't failed me yet. Linda, WME, et al.

I agree with Linda-check the stat on the stove and use IR or a good thermometer to check exact water temp. Leave it in for a while and see if it stays open. You're looking for specs and behavior.

Agree with WME, bad mojo to mix coolants.

Alas, at 105K mi, I think, do not rule out overlapping issues.


The hole-drilling is usually to cure the water temp / gauge slamming into the trouble-zone 3-5 min after startup, ditto the $60 "special" stat that Toyota will sell you with an additional smaller opening to cure same. Once they're open, it's about flow.


Because you were running at "above half" at the beginning,... do a careful check of temp gauge sender-unit per fac.manual specs. Again, like Linda said on the stat, kitchen stove, kitchen-thermometer will work, but will need ohmeter here.


That said, I have now owned 4 of these little beasts, both carb'd and injected and will report that I have bought new 3-row radiators (not aluminum, made in Mexico) that were bad out of the box and, upon inspection were just badly built. I talked to the owner at 22 RE Performance, the most premium engine builder I know of some time ago, and he told me that he had so many problems with these MIM one's, that he has them, brand new in boxes, stacked up in the rafters of his shop. This was also confirmed by YodaMan in my home area in Cali. He paid for repairs on one of mine and several others under warranty, and won't touch them now.

My last radiator purchased was aluminium because of the high cost of a responsible copper/brass rebuild and it's just OK so far. I have kept the old style copper core and will pay to re-build "next time".


Other thoughts, timing correct? Is engine breathing easy? i.e. air box, filter, any obstruction in intake air flow?


I don't know your skill level, but I'd do both a hot compression check and combustion gas test in water in the driveway, or like Linda said, mobil guy can do this easily. Especially if your guy's telling you the head's the problem and want's to send you to another shop. I keep hearing about "these guy's" who do work on your rig, then want to send you to another mechanic. It's becoming a thing these days and I think it's not a good sign.

You keep good notes, that will help.




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Young Sage,


I disagree with your contention that head gasket combustion pressures cracked your radiator and that's an indicator you have a leaking head gasket.  The radiator cap opens at under 20psi, (likely 15) which is fairly low pressure and won't damage a radiator.  If you suspect combustion gases in the cooling system, go buy the kit at any auto parts store that will confirm/deny. 


Compression checks are not a good test for HG issues.  A leak down test would be appropriate for that, but it will also be inconclusive as air can leak out the valves or other places.  If you are not losing oil, or coolant, then get a kit to test for combustion components in the coolant.  You can also send a sample of your oil to Blackstone Labs and they'll tell you if you have combustion components in the oil.


I know it's tempting to one day decide to "get it over with" and write a $3000 check, but I think you're still in the "what's going on" phase.  Find the problem. Then take appropriate action.  The 22RE is not known for head gasket issues.  I still have suspicions on the fan clutch, the thermostat, and the dash guage regarding your "overheating".  


If I were spending your money, I'd simply buy an aftermarket coolant temp guage and then see what the ACTUAL temps are.  If high, then buy the kit and send oil to Blackstone, test the thermostat.  If still no issue found, replace the fan clutch (is your shroud still in place, btw?).


I'm kind a new here, so to help you guage my input I'll tell you my background.  Former vehicle developer for GM, former worldwide powertrain planner for GM, former vehicle developer for Lexus.  Restoring cars and rebuilding engines has been my hobby since I was 15 and I'm now 62 and still hard at it.  So, don't give up and write that check.  It's something simple and you've got a few things to check first.

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Im overwhelmed with these incredibly helpful responses and encouragements. Thank you team. I will stay the course and move slowly on this. 


THank you Idaho Doug for these wise words: 


“I know it's tempting to one day decide to "get it over with" and write a $3000 check, but I think you're still in the "what's going on" phase.  Find the problem. Then take appropriate action.  The 22RE is not known for head gasket issues.  I still have suspicions on the fan clutch, the thermostat, and the dash guage regarding your "overheating".  


If I were spending your money, I'd simply buy an aftermarket coolant temp guage and then see what the ACTUAL temps are.  If high, then buy the kit and send oil to Blackstone, test the thermostat.  If still no issue found, replace the fan clutch (is your shroud still in place, btw?).” 


Yes. Fan shroud is still in place. 


I will get an aftermarket coolant temp guage. If high I will send oil to Blackstone and then test the thermostat. I have a fan clutch but it seems healthy. 


Here’s a video of the fan stopping suddenly after turning the engine off: 



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When the fan cycles it becomes loud and then you hear it wind back down when it cycles back off. You cannot miss the sound of it cycling while you are driving and hear it clearly in the cab. If you are not hearing the fan cycle on and off while driving there is an issue with the fan clutch. 

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Thanks Scott iv. I don’t recall hearing the fan engage profoundly and loudly now that you mention it. I will investigate. 


What after market coolant temperature gauge do people recommend? I believe I would prefer the mechanical style and feel that the best place to deploy it would be the upper radiator hose, employing one of these:  


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It seems there are no detectable combustion gasses in the coolant. 


I am still suspicious of the fan clutch. It freewheels for 4-5 seconds at the end of the video. This could be because the fan was not engaged in its louder state when I turned the engine off. 

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I recently used that adapter with success on another classic vehicle we have.  Worked extremely well.  However, the guage I chose was based on its features of having an audible alarm if it got hot and also that it records the max temp, etc.  Unfortunately, the backlighting is so dim that during the day it is nearly unusable and I have to ask my wife what the temp is as I cannot lean down to the dash and stare while driving, while she can.  Here is that one:




On the fan, I'd call that inconclusive as the temp guage was showing less than half way, so the fan clutch was getting hit with warm air, but not too hot air which would cause it to thicken the silicone fluid inside and engage the fan aggressively.  So, since the guage was not showing too warm (typical for idling - no load) I'd not expect the fan clutch to be engaged.  The way to test that is to drive it till it's overheating, then pull off, immediately shut down, pop the hood and see if the fan has massively higher resistance to turning than when you check it stone cold.  If that's a no, replace the fan clutch.  Honestly, these are pretty cheap and after 40 years I'd replace it with an unresolved overheating issue as a logical step.

Edited by IdahoDoug
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No exhaust gas in the coolant is good. If no milky color in the oil or milky foam on the oil cap, then head gasket is not as likely. I disagree with Idaho Doug's analysis of when the exhaust fan is triggered. My 22re rarely gets past 1/4 way on the temp gauge. When it slightly creeps above 1/4" I hear the exhaust fan trigger.  When my exhaust fan was not working properly I was getting 3/4 temp gauge readings and higher. 

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Temp gauges are typically designed such that normal full operating temp is about at a gauge's halfway mark.  So it would be a safe assumption that above that mark the vehicle's cooling system would be designed to respond.  In a modern car, an electric fan would engage.  In this 40 year old design, the silicone is designed to engage the clutch.


Factory guages are also notoriously inaccurate. That your gauge shows 1/4 when the coolant is deemed hot enough for the cooling system to respond is likely due to the gauge itself being inaccurate.  It's decades old and that's not an unusual thing.  My gauge is actually still in line with the way it was intended - settling right at the halfway mark once warmed up.  It may be a fluke, or due to the extremely low miles on my Sunrader.  


In sum, you disagree because of a sample of 1 - your own gauge.  But the halfway mark is typically where temp gauges are designed to sit to make it easy for a driver to notice a difference in either direction and this is where all 4 of my classic Toyota's temp gauges sit when fully warmed up.


PS - if you truly meant "exhaust fan", then we may be speaking of two different things.  Toyota had exhaust fans that were electric fans that pushed hot air out of the engine compartment on some models.  This was in addition to the regular radiator fan and located farther back in the engine bay next to the engine.  If that's what you are discussing, please say so as that's worthy of discussion if he has one on the vehicle we're discussing.

Edited by IdahoDoug
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doug, you seem to be mistaken about how the toyota fan clutch works.  silicon doesn't get thicker with heat.  the front of the clutch has a bimetalic coil which changes passages inside to redirect the fluid to cause lock up. the temp it works at is kind of random, i think mostly due to age. new ones are really better than the ones originally installed 

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Not to start a pissing match, but my description was conversational, not technical.  Please dont be offended by this as obviously you didnt know. But here we go.

I've personally modified 3 Toyota viscous fan clutches by changing the silicone fluid to a higher viscosity.   I've also rebuilt a rare Vanagon Syncro viscous coupling, and developed and sold a kit instructing other Syncro owners how to do it to restore as new operation on a 30 year old component.


Prior to that, I was Worldwide Powertrain Planner for GM, and worked on our first AWD system which used viscous couplings on all 4 hubs.  Yes, heat changes the viscosity of silicone fluid, and this property helps the Toyota VC fan clutch come close to full lockup when needed when things get very hot.

You are also correct these age and do not respond as new, and the deterioration causes it to lockup less and less.  Which is why I suggest he get a new one to restore as new cooling.  Ironically, one of the mods I will inevitably do is to drain and refill my Sunrader's fan clutch with a slightly thicker silicone fluid - trading off a bit of mpg for a lot more cooling.  

Hopefully I have not offended with my "over answer"  - it's easy to do on a forum where the posts take on a back and forth quality that would not happen if we were sitting around a campfire. Which one day I hope we do!!


Regards, Doug

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Hello Friends, 

Current possible solutions to my overheating situation are these: 


- I have ordered a new coolant temperature sending unit. Perhaps the one from 1988 suddenly began giving inaccurate readings after I got all of this work done. 


If I don’t want to use the original temp gauge in the dash and was more keen to get an accurate numerical readout, why wouldn’t I just poke a sensor from a mechanical water temp gauge in that hole instead and forego the stock gauge on the dash?  Has anyone done this? Are there adaptors that need to be employed? 


- If I wanted to have both the stock gauge operational and have an additional gauge with exact degrees, where would be the best place to mount the sensor for the mechanical gauge? I have heard of people splicing them into the upper radiator hose and also have heard there are water necks that have a port in them for a sensor. My water neck does not have a port but perhaps I could acquire one. 


Again, the increase in heat of my engine was a sudden onset. It did not get anywhere near this hot before I had the work done.  I suspect it has something to do with the new radiator (CSF  - apparently known for meticulous quality control), the new thermostat, or perhaps something to do with the removal of all Air Conditioning components. Is there a relationship/point of connection between the AC system and the cooling system of the 22re? 


And lastly, I ordered a new fan clutch and am planning on replacing the old one with this new one. 


Here’s a picture of what I believe is the temperature sending unit for the dash gauge. 


Again, many thanks for your thoughts and reflections. I am indebted. 


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To have BOTH a factory guage and a digital aftermarket one is wise on a 40 year old.  But wait on that. Once you install the new factory guage sender and the new fan clutch - see where you are.  I expect all will be right with the world.  

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  • 3 weeks later...



I replaced the fan with a flex fan from LCE engineering as it sounded like it might move more air. Some have said I should switch this out for a new clutch fan. Any experience here with the LCE flex fans? 


I replaced the sending unit for the gauge on the dash. 


I put in a 170 degree thermostat. 


Same issue. Overheating on grades (see photo documentation). 


I spoke with a man at 22RE Performance in Chico, CA. After hearing my overheating story he asked me, “you didn't put a CSF radiator in there did you?” To which I answered, “Yes. A three-core one. Top dollar.” 


“That’s your problem”, said he. 


So… I am now zeroing-in on a different radiator option to the CSF as that fits with the timeline of this story and the title of this thread.


This was a SUDDEN ONSET overheating situation, initiated by the installation of the CSF radiator.


I am in discussion with the fine people over at Mishimoto Radiator and am looking at their all-aluminum “race radiators” - about as pricey as the CSF but I think maybe a solution for me. The other option I was considering was finding a radiator repair place to flush, clean, and repair my old radiator and have that one re-installed. Another option is to get one of the OEM $119 dollar, plastic/aluminum radiators.


THree options I have before me at present. 


Does anyone have any thoughts on the most bomber radiator for the 22RE (auto trans) that is NOT a CSF? I’d love to hear some thoughts on this. 


I’m including a picture of the gauge after my most recent test, climbing Siskiyou Pass with the new 170 degree thermostat, sending unit, and flex fan. 




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put the right thermostat back in. it isn't the problem, but the wrong one can cause problems.

  the flex fan will decrease your milage. also noisy . go back to fan clutch. 

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p.s.  if that gauge reading is from within the last few days, i think it's not out of line. it's hot out

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I plan to put the fan clutch back in and will probably do the same with the Thermostat. But what radiator, team? I will be removing the CSF as I truly believe that is the cause of this sudden onset problem. Who’se got an idea for a decent -ideally way-more than decent- radiator? 



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