93-97 Coolant Temperature Gauge Modification (9 Viewers)

[winstonclein]

2 more gauge temp mods done in Houston, TX.
1 on a 94 and another on a 97
Not hardcore tested (Houston's traffic 4th worst in USA and over 100* in 32 days in a row this summer so far), but working properly up to now.
Thanks!!!

 

[Dave 2000]

Nice one, you will not be disapointed! I climbed a sea level to 1000 metre hill a couple of days ago at a steady 70 MPH, temps outside 39 Celsius (102 F......ish?) and with the A/C on the gauge was showing just under 3/4 which is the highest I have seen, before mod the damn needle never moved past centre.

regards

Dave

 

[CO_Hunter]

RT, Thanks for an awesome mod!

I have found I am running warmer than I thought. Normal around town and highway will vary from 1/3 - 1/2 ( in town) to 3/4 (hwy) ambient 60's to 80's.

Climbing Monarch Pass (loaded with few hundred pounds) I got to the bottom of the red. Then slow moderate to steep 4 wheeling, it was bottom of the red as well and maybe a tad over (ambient was ~70). I'm thinking fan clutch (original) service may be in order, I do have just under 200k miles.

I have new hoses, thermostat (Toyota) last year, complete flush/backflush each of the last two years. Refilled with green.

I just took this pic idling in the driveway (ambient mid 70's).

 

[semlin]

is that with the engine warm? if so, it's way lower than mine at idle. is it possible you installed the t-stat wrong?

 

[CO_Hunter]

Engine was warm and running but I did have the hood up for a while when I was working on timing. I guess it is possible the t-stat is in wrong but doubtful as I'm very particular about my work. I'm intrigued by how you think an improperly installed t-stat may be responsible for the behavior? Seems like installing it backwards would cause an overheat. I have a thermometer on a multimeter which read about 163* on the top aluminum coolant tube.

 

[RavenTai]

that is about where 163 should be on the gauge, 163 is low for an 80 that is up to temp, it should be 180 to 190 or so, was the heat on? if the heat is runnign and its cold enough you can under cool the engine at idle, otherwise the thermostat is suspect, was it an OEM toyota?

 

[semlin]

Engine was warm and running but I did have the hood up for a while when I was working on timing. I guess it is possible the t-stat is in wrong but doubtful as I'm very particular about my work. I'm intrigued by how you think an improperly installed t-stat may be responsible for the behavior? Seems like installing it backwards would cause an overheat. I have a thermometer on a multimeter which read about 163* on the top aluminum coolant tube.

whoops, i need to press quote instead of edit. sorry.

i am thinking the o ring seal or that little toggle or maybe something stuck might be allowing limited flow that prevents the engine from heating up enough at idle to open the t-state. 163 seems way low.

 

[CO_Hunter]

The t-stat is OEM Toyota straight from C-Dan. I just checked it again with the hood down and got the same idle temperature. Heat was off. If anything, it seems it is opening too early. Odd that I seem to have both low temperature and high temperature issues.

 

[RavenTai]

You did put the tstat gasket on both sides of the tstat flange correct? In othere words the sheet metal sits in a slit in the gasket? You put thegiggler valve at 12 o clock.?

 

[CO_Hunter]

I can't recall for certain on the gasket but I would be surprised if I did it wrong. As for the valve, I'm certain it is a 12 o clock. So much has been said on that topic and was identified in the back flushing thread I used as a reference.

 

[semlin]

well your engine is behaving like a vehicle with a partly stuck open t-stat. it doesn't warm up properly at idle and then it overheats under load.

 

[CO_Hunter]

I did a bit more looking into this as it would be easy to test Semlin's idea. I let the engine run at idle and I checked the temp of the top hose by hand to see if it warmed gradually or quickly. The hose did not warm until the temperature reached what is shown in the picture. If was partly stuck open then it seems there would be a gradual warming therefore I don't think that is it.

I was thinking of changing the fan clutch oil so I took off the fan clutch to see if I had the blue hub or original (I'm the 3rd owner) and look it over. Not blue but I don't know if it is the original or an aftermarket, I did not take the fan off the clutch. Does this pic help? When I held the hub and spun the fan I could get about one rotation. If I kept spinning the fan it would essentially free wheel. Seems like this isn't right.

 

[Dave 2000]

RT, Thanks for an awesome mod!

I have found I am running warmer than I thought. Normal around town and highway will vary from 1/3 - 1/2 ( in town) to 3/4 (hwy) ambient 60's to 80's.

Climbing Monarch Pass (loaded with few hundred pounds) I got to the bottom of the red. Then slow moderate to steep 4 wheeling, it was bottom of the red as well and maybe a tad over (ambient was ~70). I'm thinking fan clutch (original) service may be in order, I do have just under 200k miles.

I have new hoses, thermostat (Toyota) last year, complete flush/backflush each of the last two years. Refilled with green.

I just took this pic idling in the driveway (ambient mid 70's).

View attachment 559316

Normal idle and runnig around town I would see a reading about half the needle thickness higher?

regards

Dave

 

[mudking82]

I have found I am running warmer than I thought. Normal around town and highway will vary from 1/3 - 1/2 ( in town) to 3/4 (hwy) ambient 60's to 80's.

Climbing Monarch Pass (loaded with few hundred pounds) I got to the bottom of the red. Then slow moderate to steep 4 wheeling, it was bottom of the red as well and maybe a tad over (ambient was ~70). I'm thinking fan clutch (original) service may be in order, I do have just under 200k miles.

I have new hoses, thermostat (Toyota) last year, complete flush/backflush each of the last two years. Refilled with green.

I just took this pic idling in the driveway (ambient mid 70's).

View attachment 559316

Interesting, as I have the same thing happening in terms of running cold seemingly. Your picture there is where mine runs almost all the time after it warms up. I don't think I have ever even seen the needle go to the halfway mark since I modified it. Just put a new radiator and t-stat in also, and yes, it is factory Toyota t-stat installed correctly, as was the previous one that acted the same on the gauge. Perhaps I should check out my actual temp sensor.....

 

[Gerard Bodde]

I have the same thing, cold when offroading but warm on the highway, would have thought that the airflow on the highway would cool it down more. I am considering adding an electrical fan

What I do not understand is why mine climbs closer to the red on the highway but around town she sits at the 3/4 mark. After the readings with the IR I feel better but still curious why it climbs on the highway.

I just thought I would post and see if anyone else had the same problem after the mod.

 

[TomH]

My needle is running about the same place as CO_Hunter. I replaced my aftermarket thrmostat with a Toyota thermostat and nothing changed.

Gauge performance was as expected when I first did the mod so it appears something changed that is causing the motor to run cooler.

After I made the post above, I did a fully loaded camping trip and the temp approached the high end of the gauge - as expected, so I really think the gauge is functioning properly.

I just have no idea why it would be running below the thermostat setting.

 

[91Chevota]

To anyone concerned:

I did the temperature modification using the 100 and 150 ohm combination on my 1991 FJ80, and I found that my temperature sensor was making the gauge read way off even though it was within spec. In checking, the 1991 temp sender and the 1993 on up are two different part numbers. It may be that this doesn't work as well for the early FJ80s.

Using my infrared temp gun, at mid-point I was at 161 degrees, and I hit the bottom of the red at 193 degrees. I turned off my fan to get it to peg hot, and when the gauge pegged hot, I was at 219 degrees.

I still think it is a great mod, but if you are going to do it with a 91-92 model you might want to consider using the later model temperature sender.

 

[CO_Hunter]

I guess I should have posted an update. I had saved my old t-stat as a spare so I pulled the new one out of the engine and tested both in boiling water. The newer one opened early, this was causing the lower temps. I put the old one in it now is pretty much in the middle and varies a little while driving, as one would expect. Even in cold weather it warms up nicely. So much for changing the t-stat as pm.

As for the fan, I found it was the origianl so I changed the oil to 10,000 weight and it sure did tighten it up. It's been too cool to test it out for high end temps but I suspect that will fix the problem. Never would have found these had it not been for this mod

 

[RavenTai]

To anyone concerned:

I did the temperature modification using the 100 and 150 ohm combination on my 1991 FJ80, and I found that my temperature sensor was making the gauge read way off even though it was within spec. In checking, the 1991 temp sender and the 1993 on up are two different part numbers. It may be that this doesn't work as well for the early FJ80s.

Using my infrared temp gun, at mid-point I was at 161 degrees, and I hit the bottom of the red at 193 degrees. I turned off my fan to get it to peg hot, and when the gauge pegged hot, I was at 219 degrees.

I still think it is a great mod, but if you are going to do it with a 91-92 model you might want to consider using the later model temperature sender.

There are actually three groups of gauges by part number, 91/92, 93/94 and 95-97, the mod was originally for the 95-97, it was later expanded to include 93/94 although there are physical differences between the 93 and 95 gauges they are electrically the same, or at least electrically similar enough for the mod to perform its function,

unfortunately I did not have access to a 91/92 gauge or vehicle to work with while cooking up the mod you have gone further than anyone else with that year group, the 3fe engine held over from the FJ62 is significantly different from the 1FZ of the later cruisers, uses a different sender, weather the later sender would bolt up on the 3FE is unknown.

 

[RavenTai]

I guess I should have posted an update. I had saved my old t-stat as a spare so I pulled the new one out of the engine and tested both in boiling water. The newer one opened early, this was causing the lower temps. I put the old one in it now is pretty much in the middle and varies a little while driving, as one would expect. Even in cold weather it warms up nicely. So much for changing the t-stat as pm.

As for the fan, I found it was the origianl so I changed the oil to 10,000 weight and it sure did tighten it up. It's been too cool to test it out for high end temps but I suspect that will fix the problem. Never would have found these had it not been for this mod

very cool