When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Well as per usual, I can’t leave well enough alone…… my AC was not working. So I ran through all the usual checks. Everything looked good, checked system for a leak and it passed, pulled a vacuum for 45 minutes, charged it up….still wasn’t working. Last thing I decided to do was change out both Coolant sensors. The brass sending unit and EC1 right next to it. Well needless to say I broke off the bed sending unit in the coolant block. Obtained another one and got it installed. AC started working.
The temp gauge was running just slightly higher than the other one that was in it when I bought the truck.
This morning I noticed that it was leaking coolant from the sending unit where it threads into the coolant block. So I remove the sensor, clean stuff up a little and reinstall.
I just took it to the gas station and when I turned the truck back on the temp gauge started to rise near the red for a few seconds, then dropped right down to the middle where it normally sits.
Im starting to think that the sensor was never the issue but rather the wiring may have had a loose connection that I fixed.
My next question is to why it’s now spiking when turned off and then back on again…. I know there wasn’t a huge air pocket in there… Not really possible from swapping the sensor. I know there will be heat soak when the coolant stops flowing also
I ohmed out the sensor I put in and it was .553 Ohms.. The FSM says it should be 2.3kOhms.
Here are three pictures. First one is when I turn the truck back on. The s cons one is about a minute in, and the 3rd picture is when I hit the gas.. I took it for a short drive and it will stay where the 3rd picture is.
It's called "Heat Soak". When you run the truck for a reasonable length of time, obviously, the truck will warm up. It's controlled by the fan, controlled by the fan clutch. It maintains a normal temperature while driving, in other words.
If you stop, the heat in the block and head(s) then goes into the coolant, as it should. Thus, the coolant gets really hot, the thermostat opens up wide, and the coolant slowly starts to cool down. It gives up the heat to the air, mainly from the radiator, but also the metal parts of the engine with coolant in them, and the coolant hoses. Again, normal. There just no air flowing through the radiator, nor coolant flowing around in the rest of the engine.
You then start the truck, The hotter-than-normal coolant now starts to flow over the sensor, causing the indicated temperature of the truck to rise up to a high, almost too high, but not quite. It cools very rapidly, as now, the engine is running, the fan is sucking air through the radiator, and the cooling system is functioning perfectly normally.
If you look under the hood within about 5 or 10 minutes of stopping the vehicle for a while, after it gets good and warm, you will see the recovery tank much fuller than normal. This is due to the heat it's absorbing forcing coolant out of the radiator. If you then start the engine, you will see the level of coolant in the recovery tank drop rapidly, as the engine cools down, and the radiator draws the coolant back out of the recovery tank.
In other words, heat soak is a perfectly normal event. Something that will help reduce the occurance of heat soak showing up on the gauge, is to get one of the Toyota 2-stage thermostats. It will allow the hot coolant to flow faster, thus lowering the appearance of the heat soak on the gauge in the gauge cluster. IMHO, when you put the new sensor in, you allowed you to see the high rise in the coolant temperature. The old gauge didn't react fast enough, or to high enough a temperature, something like that, to see the effect of heat soak. Alternatively, you just never noticed the effect. I used to live in Yuma, AZ, and saw this effect in my 87 4Runner, which I have since sold off, all the time. By the same token, in Yuma it was often over 110°, soooooo...
It's called "Heat Soak". When you run the truck for a reasonable length of time, obviously, the truck will warm up. It's controlled by the fan, controlled by the fan clutch. It maintains a normal temperature while driving, in other words.
If you stop, the heat in the block and head(s) then goes into the coolant, as it should. Thus, the coolant gets really hot, the thermostat opens up wide, and the coolant slowly starts to cool down. It gives up the heat to the air, mainly from the radiator, but also the metal parts of the engine with coolant in them, and the coolant hoses. Again, normal. There just no air flowing through the radiator, nor coolant flowing around in the rest of the engine.
You then start the truck, The hotter-than-normal coolant now starts to flow over the sensor, causing the indicated temperature of the truck to rise up to a high, almost too high, but not quite. It cools very rapidly, as now, the engine is running, the fan is sucking air through the radiator, and the cooling system is functioning perfectly normally.
If you look under the hood within about 5 or 10 minutes of stopping the vehicle for a while, after it gets good and warm, you will see the recovery tank much fuller than normal. This is due to the heat it's absorbing forcing coolant out of the radiator. If you then start the engine, you will see the level of coolant in the recovery tank drop rapidly, as the engine cools down, and the radiator draws the coolant back out of the recovery tank.
In other words, heat soak is a perfectly normal event. Something that will help reduce the occurance of heat soak showing up on the gauge, is to get one of the Toyota 2-stage thermostats. It will allow the hot coolant to flow faster, thus lowering the appearance of the heat soak on the gauge in the gauge cluster. IMHO, when you put the new sensor in, you allowed you to see the high rise in the coolant temperature. The old gauge didn't react fast enough, or to high enough a temperature, something like that, to see the effect of heat soak. Alternatively, you just never noticed the effect. I used to live in Yuma, AZ, and saw this effect in my 87 4Runner, which I have since sold off, all the time. By the same token, in Yuma it was often over 110°, soooooo...
Does this babbling answer your concerns?
Pat☺
Pat,
Thanks for the info. I understand heat soak and realize that its gong to marginally move the gauge. I guess I didnt specify that I was a little concerned with the actual gauge or the replacement sensor itself. There are a few other things going on with the 4runner that I neglected to include in the post. First thing is I believe the TPS is out of whack because I cannot get it into base timing when I jumper the Pins in the Diag port(Plus it failed all the FSM tests), Its hard to start when cold or has sat all night and doesn't like to idle until it warms up for a few minutes, and lastly.....The temp gauge jumps to nearly operating temperature only after about a minute of run time from cold. I Have had a ton of Toyotas ....But only one 3vze... There are multiple issues that I am trying to sort out. First and foremost is the TPS. I have another one coming that I need to install to try and fix one issue at a tie.
.I replaced the Gauge sender and the ECT with aftermarket variants from a local parts house. I think I might reinstall the original Gauge sender and see how the gauge in the truck responds. Also....Since I am a little foggy on the 3vze....is the Thermo time switch on the passenger side in on the coolant port next to the thermal vacuum valve? I need to crack my CSI and see if its spraying when cold.
I guess my question should have been.......... Have you ever had an aftermarket sender make the gauge do that, or was it more likely the gauge in the dash itself?
Thank you again for all the information and the in-depth explanation on heat soak!
It feels good to be back in the seat of another Toyota!!
I Apologize. I didn't realize you already knew about heat soak. I have a problem giving way more info than is required.
I wouldn't use aftermarket anythings unless forced to. The gauge going to "normal" within 1 minute or so after a cold start is a sure fire indication something in that circuit isn't right. I would go back to OEM wherever possible. Also, don't put anything on the sender's threads, such as teflon tape, antisieze, and so forth. The threads of the sender should be clean and dry before installation. Both the sender unit AND the place it screws into. If needed, you can follow the threads to ensure they're in good shape, and that the sender screws in correctly.
That gauge circuit isn't reading anywhere close to right. Is it OK once the engine actually warms up? Who knows, but personally, I wouldn't trust the circuit. Re-replace the parts one at a time. I would start with the sender, if it were me. Just me, though, you do you
Definitely get the TPS to align properly. It may not affect the way the temp gauge reads, or it may. I don't think it would, but I've been wrong before. MANY times
I don't think the TPS is the cause of the timing aligning properly. It's the distributor, or the timing belt, being off. Again, lots of things I am not a pro on. Check the distributor lines up correctly when the crankshaft is indicating #1 is at TDC. Make sure that it is #1 at TDC. It can be 180° out when it appears to indicate #1 is TDC. Easiest is to put a small straw in the spark plug hole, and let it do the work. Another way, and technically the "correct" way, is to pull the valve cover off, and the turn the crank until it indicates 0°. Check the valves of the #1 cylinder are both loose. If not, rotate the crank one complete rotation. Then check the distributor rotor is pointing directly at the #1 tower. About 10 o'clock. If it's just a little bit off, the distributor can be adjusted to bring it into alignment. If it's very much off, you may need to restab the distributor. Remember to ensure the crank is pointed right.
I'm doing it again, aren't I? Too much info. Sorry!
Pat☺
I Apologize. I didn't realize you already knew about heat soak. I have a problem giving way more info than is required.
I wouldn't use aftermarket anythings unless forced to. The gauge going to "normal" within 1 minute or so after a cold start is a sure fire indication something in that circuit isn't right. I would go back to OEM wherever possible. Also, don't put anything on the sender's threads, such as teflon tape, antisieze, and so forth. The threads of the sender should be clean and dry before installation. Both the sender unit AND the place it screws into. If needed, you can follow the threads to ensure they're in good shape, and that the sender screws in correctly.
That gauge circuit isn't reading anywhere close to right. Is it OK once the engine actually warms up? Who knows, but personally, I wouldn't trust the circuit. Re-replace the parts one at a time. I would start with the sender, if it were me. Just me, though, you do you
Definitely get the TPS to align properly. It may not affect the way the temp gauge reads, or it may. I don't think it would, but I've been wrong before. MANY times
I don't think the TPS is the cause of the timing aligning properly. It's the distributor, or the timing belt, being off. Again, lots of things I am not a pro on. Check the distributor lines up correctly when the crankshaft is indicating #1 is at TDC. Make sure that it is #1 at TDC. It can be 180° out when it appears to indicate #1 is TDC. Easiest is to put a small straw in the spark plug hole, and let it do the work. Another way, and technically the "correct" way, is to pull the valve cover off, and the turn the crank until it indicates 0°. Check the valves of the #1 cylinder are both loose. If not, rotate the crank one complete rotation. Then check the distributor rotor is pointing directly at the #1 tower. About 10 o'clock. If it's just a little bit off, the distributor can be adjusted to bring it into alignment. If it's very much off, you may need to restab the distributor. Remember to ensure the crank is pointed right.
I'm doing it again, aren't I? Too much info. Sorry!
Pat☺
Pat....NEVER say sorry for too much information. I do the exact same thing! I enjoy talking to people that have knowledge on something I am a little foggy these days. I have been away from the Toyota scene since 2017 and I have not really messed with anything 85-95 Toyota since about 2015....So my recollection of somethings are a Little unclear. So Please by all means....pour it on my man!!!
I did remember that the TPS being out of adjustment will not allow the engine to go into base timing. I adjusted the TPS and was able to get it in and set the timing to 10 degrees BTDC. It runs like a whole different animal now!
And I swapped the OEM temp sensor back in and the gauge Is not all crazy anymore. It takes the proper time to come up to normal operating temp and then it stays there. I think I need to snug it down a little more though. Every once in a while it will seep and drip coolant onto the crossover pipe. I am afraid to break another one off. ha .
Use the method I’ve posted several times on how to set the TPS using a timing light. My instructions were written for a 22RE, but it works on the 3VZE.
it’ll be vastly faster and much more accurate than the FSM. And if it makes you feel better, it’s the method that Toyota’s Tech Line (TAS) eventually endorsed, and used broadly by dealer techs back when 22R’s ruled.
curious, was the new temp sensor oem? If so we’re did you get?
06-06-2023, 11:45 AM
