How is that?
The hottest water would be on the outlet, not the inlet.

False.
The Expanding-Wax-Pellet on the under-side of the Thermostat is
the mechanism used to cause the Thermostat to open.
Therefore, the "back-side" or "bottom" of the Thermostat must have
a steady circulating flow Coolant passing it at all times.

When the Wax-Pellet expands from increasing temperatures,
Coolant is then allowed to flow through the Radiator.

When the Thermostat is "closed", a separate path must be provided for
continuous Coolant circulation throughout the Engine.

Continuous Coolant circulation is required to maintain
even Coolant temperatures in all of the various parts of the Engine,
at all times.

The Thermostat only regulates Coolant flow through the Radiator,
it does NOT regulate Coolant flow through the Engine.

Coolant flow is constant/continuous in the Engine Block and Head(s).
Coolant flow through the Radiator is intermittent or "cyclic".

 

geekoftheweek you are right. I did some internet searching and there are a few examples of the thermostat located on the inlet on the engine.

I went out and checked the thermostat location on my 2018 GMC pickup with a 5.3 V8 and my wife's Honda Civic both have the thermostat on the outlet.

The rad hoses are not a good location for a temp gauge.

I don't remember what year exactly the old man's truck was, but it had the 5.7. I guess I kind of made some assumptions I shouldn't have. In a way it really doesn't make sense, but it works.

 

There is nothing wrong with your new Gauge, or its Sensor.

Other than the Cylinder-Head or Engine-Block Coolant-Passages,
the only reliable readings will be from your Coolant-Bypass-Hose(s).

This function allows the continuous circulation of Coolant throughout the Engine
regardless of the Thermostat being open or closed.
It keeps the Coolant at a constant, even, Temperature throughout the Engine.

You may not have a separate, dedicated, Coolant-Bypass-Hose.
The Coolant-Bypass-Hose Function may be integrated into the Heater-Hoses,
where a Bypass-Style-Heater-Valve
either recirculates Coolant directly back to the Water-Pump,
or sends it to the Heater-Core inside the Car first,
and then sends it back to the Pump.

You need to know which direction the Coolant flows in if you use the Heater Hoses,
you need the Hose that is coming from the Cylinder-Head,
not the Hose returning to the Water-Pump.
The Hose returning to the Water-Pump
will be colder in the Winter-Months when the Car's Heater is on.

Installing a solid Brass-Tee-Fitting in this Line,
with the appropriate adapters,
will give you a perfect location for your new Temp-Sensor.

If you are not familiar with the Hose Routing on your Engine you may have to
take it to a shop that works on Minis and tell them what you are attempting.
Buy them Lunch and your likely to get a friendlier attitude.

Thanks. I understand this conversation. I don't know how the water travels around and through the engine. I do know where the pipes from the radiator reside and the out arrow on the thermostat connects to the hose traveling to the top of the radiator. There is no way to tap the heater hose. They are specific and closed most of the time. There is no bypass. That would be internal to the mini thermostat. I have no codes on the thermostat telling me it's not opening or closing as expected. And there is only one place to tap the hot water on the hose at the top of the radiator. I called Mini today. My only theory is that there is air in the system and I need to vacuum fill it again. It's been opened and refilled many times due to this mystery gauge problem. It appears full but maybe not.

 

How is that?
The hottest water would be on the outlet, not the inlet.

I know I'll never find where I saw the explanation for it, but from what I remember it had to do with how the coolant enters at a temperature too low to be able to be heated to the same temperature as it left. Having the thermostat on the inlet allows for a more consistent blend of internal circulation and cooled coolant is what it amounted to.

 

False.
The Expanding-Wax-Pellet on the under-side of the Thermostat is
the mechanism used to cause the Thermostat to open.
Therefore, the "back-side" or "bottom" of the Thermostat must have
a steady circulating flow Coolant passing it at all times.

When the Wax-Pellet expands from increasing temperatures,
Coolant is then allowed to flow through the Radiator.

When the Thermostat is "closed", a separate path must be provided for
continuous Coolant circulation throughout the Engine.

Continuous Coolant circulation is required to maintain
even Coolant temperatures in all of the various parts of the Engine,
at all times.

The Thermostat only regulates Coolant flow through the Radiator,
it does NOT regulate Coolant flow through the Engine.

Coolant flow is constant/continuous in the Engine Block and Head(s).
Coolant flow through the Radiator is intermittent or "cyclic".
.
.
.

So that would explain the gauge temp going up and down. However, even when the coolant in the surge tank is hot the gauge can still say 0 degrees. And when I measured the resistance of the sender after driving for about 20 minutes this morning it was over 1,000 ohms indicating a temp under 100 degrees, but not true. If I measure the temp with a scan tool of course it is giving me the water temp at the thermostat which is a digital signal handled by the brain. There is another tap on the oil filter which is water cooled but I'm not sure if it's for water or oil. It's also really difficult to access.

 

If your Gauge ever reads "0" degrees,
(and it's not actually below freezing cold outside),
you probably have a bad Ground connection to the Sensor.

You may not have an appropriate place to mount your Temp-Sensor.

Does your Car "only" have an "Idiot-Light" for Engine Temps ????
That's unusual in modern Cars.

There are Gauges which plug into your Diagnostic-Port and get their
info from the ECU via the Car's "CAN-Buss" Data-Link,
but you'll pay dearly for that convenience. ( starting at ~$150.oo ).

 

If your Gauge ever reads "0" degrees,
(and it's not actually below freezing cold outside),
you probably have a bad Ground connection to the Sensor.

You may not have an appropriate place to mount your Temp-Sensor.

Does your Car "only" have an "Idiot-Light" for Engine Temps ????
That's unusual in modern Cars.

There are Gauges which plug into your Diagnostic-Port and get their
info from the ECU via the Car's "CAN-Buss" Data-Link,
but you'll pay dearly for that convenience. ( starting at ~$150.oo ).
.
.
.

I have a Foxwell with software loaded into it for ODB2, and Mini. So there are some generics and also codes unique to Mini. The usual running temp I’ve seen is anywhere from 100C to 107C (212-224F) It goes higher but the fan kicks in and brings it back to about 220. I have checked the meter, and then measured the resistance on the sender to see if its working. I’ve tested the ground. All the gauges have the same ground. In fact all the gauges and the other electronics have the same ground and the same power source, protected by a 10AMP fuse.

 

What is a "Foxwell" ?
Are You talking about a stand-alone CAN-Buss Temp-Gauge ?
Or a brand of Diagnostic-Code-Reader with extra features ?

 

It’s sender is located in the coolant line with the hottest water traveling to the top of the radiator after the thermostat.

The gauge does not read until the engine is hot. When the engine is at running temperature the gauge does not read consistently and in fact only reports accurately when the car s at idle in the garage after driving.

All of this could have been settled from what was said in the first post. People seem to think when an engine is running at speed there is water in the top tank of the radiator, just like at idle. Take off the radiator cap some time (while car is cold so there is no pressure) and rev the engine to normal driving RPM. Look at how much water is in the top tank, you'll see very little if any. Let the RPM's back down to idling and magically the water comes back up in the tank. Nothing wrong at all just the way it works out.

If this car is new enough to have a ECM there should be 2 temp sensors, like in most engines. One for the ECM and another for the temp gauge.

 

What is a "Foxwell" ?
Are You talking about a stand-alone CAN-Buss Temp-Gauge ?
Or a brand of Diagnostic-Code-Reader with extra features ?

A Foxwell is a scan tool with software installed to read the odb2 codes and reset them. At the moment i have no codes to reset. The only thing soecific to the mini is the software.

 

If this car is new enough to have a ECM there should be 2 temp sensors, like in most engines. One for the ECM and another for the temp gauge.

Unfortunately CAN has done away with the second sensor in most cars. The PCM tells the dash to light up the light or move the gauge these days.

 

The gauge sender goes directly to the gauge and is located in the top radiator hose. It screws into an aluminum connector I placed at the connection of two hoses.

I did some looking around online hoping somewhere along the lines someone found a better way to do this. Unfortunately it seems the only thing I could find was this type of setup which is a crap design. If you are putting a temp gauge in your car you want it to work all the time... not just when the thermostat opens.

In the old days there used to be an extra plug somewhere on the engine that you would simply take out and screw your new sensor in and everything was good. If you haven't already done so try a Mini forum and see if anyone there has ideas. They will at least have a little more information on the car and possibilities since the site is dedicated to them. We all will just guess and come up with ideas that will probably not work and just cause more frustration.

 

I did some looking around online hoping somewhere along the lines someone found a better way to do this. Unfortunately it seems the only thing I could find was this type of setup which is a crap design. If you are putting a temp gauge in your car you want it to work all the time... not just when the thermostat opens.

In the old days there used to be an extra plug somewhere on the engine that you would simply take out and screw your new sensor in and everything was good. If you haven't already done so try a Mini forum and see if anyone there has ideas. They will at least have a little more information on the car and possibilities since the site is dedicated to them. We all will just guess and come up with ideas that will probably not work and just cause more frustration.

Thanks. There is only one place for the sender to go and that is in the top radiator hose. I have some work to do this weekend and will look the system over one more time. It's always a mess. Coolant everywhere. And this gauge problem should not be a problem. It's really too simple.

 

There is only one place for the sender to go and that is in the top radiator hose.

You don't mean in the rubber hose do you? If so how is it getting the ground it needs to complete the circuit?

This brings up another question, are you trying to measure the radiator temp? If so that is usually done with a bulb type sensor like they use for add on electric fans that gets pushed into the radiator fins.

 

Unfortunately CAN has done away with the second sensor in most cars. The PCM tells the dash to light up the light or move the gauge these days.

But he is adding a gauge not going through the ECM

 

I would be willing to bet,
that if you looked at a bare Mini Engine, outside of the Car,
you would find that there are at least one, and maybe 2, threaded holes in the
Cylinder-Head, or Block, that would work just fine, possibly only requiring an
adapter to change thread sizes.

Also, keep in mind that, the Sensor doesn't necessarily have to be in direct contact
with the Coolant.
You can get accurate temperature readings by simply drilling and threading a hole
into the Cylinder-Head.
Just don't put it too close to the Exhaust-Manifold.
.
.
.

 

But he is adding a gauge not going through the ECM

Understood that part. I thought you were referring to the days when there was a sensor for the PCM and a separate sensor for the factory dash gauge / light. Just pull the factory sensor and put yours in instead...

 

I would be willing to bet,
that if you looked at a bare Mini Engine, outside of the Car,
you would find that there are at least one, and maybe 2, threaded holes in the
Cylinder-Head, or Block, that would work just fine, possibly only requiring an
adapter to change thread sizes.

It would seem there should at least be somewhere probably buried under plastic or otherwise no easy access place to do it... it would also seem that there would be a better kit somewhere. Maybe I didn't dig deep enough only checking the first page of a couple different searches, but this type of setup was all I saw. I would kind of like to take a look at one just out of curiosity now.

 

You don't mean in the rubber hose do you? If so how is it getting the ground it needs to complete the circuit?

This brings up another question, are you trying to measure the radiator temp? If so that is usually done with a bulb type sensor like they use for add on electric fans that gets pushed into the radiator fins.

The sender has two wires. GND and signal. GND is a common location shared by all the gauges and other electronics I added.

 

A lot of engines have a drain plug for draining the coolant low down on
the engine block. If your engine has one it might a usable location for
the sender.