18 replies to this topic

[DClarke1954]

1275 engine Classic Mini, probably Stage 1 or better.

 

I have been trying to find why my temp gauge isn't showing any temperature at all.

Grounding the sensor wire makes the gauge show "H" and then some.    So gauge and wiring is OK but the sensor isn't  presenting a resistance value the gauge is looking for.

I've tried 2 different senders (maybe a mismatched sender/gauge combo).

 

But, today when running the engine after refurbishing and refitting the fuel pump I noticed that the radiator and pipework all rose in temperature together at the same time and at the same rate, in fact the top of the radiator felt warmer than the top hose and heater-hoses to the touch.

 

To me, this rather suggests that someone has omitted to fit a thermostat at all.

 

I had heard that removing the thermostat was a bad idea because it meant that the coolant flow was not as god & BLMC intended it to be and cylinders 3 & 4 could overheat as all the coolant took the short-cut round 1 & 2.

This may be fact, or just an "old-wives-tale".  Happy to pull the housing to check for a stat, but before I rush into it, is it a big problem or just an urban myth?

 

Cheers!

 

Dan.

[Quinlan minor]

For use on the road, a thermostat is necessary. Otherwise the engine will be operating outside its nominal temperature most of the time.

[Steve220]

Road car - It needs to get to temp quickly for tolerances. Fit a thermostat

[Spider]

It's important to run a thermostat, as the other guys have said, to get the engine up to temperature for it's correct operation. If you read all tuning manuals, they'll all start off with words along the lines of " get the engine up to operating temperature ".

It's also needed for the Oil, which won't lubricate properly until it's also up to temperature. This will also help no end from removing moisture from the oil that enters the crankcase from the breathers and reduce the formation of acids.

 

However,,,, given your description here, I think it may have a thermostat fitted.

It's best to first establish if the gauge is in fact working. I think I asked the question in one of your other threads - what brand / type temperature gauge are you running ?

 

I had heard that removing the thermostat was a bad idea because it meant that the coolant flow was not as god & BLMC intended it to be and cylinders 3 & 4 could overheat as all the coolant took the short-cut round 1 & 2.

This may be fact, or just an "old-wives-tale".  Happy to pull the housing to check for a stat, but before I rush into it, is it a big problem or just an urban myth?.

 

Old wives' tale.
 

[Steam]

You are working on 2 different issues, they may be vaguely related but not directly.
To establish what is going on with your temp gauge you should remove the sensor and see what it does when dunked in kettle hot water, mid range on the gauge is the aim here. You could also use a potentiometer or various resistors in place of the sender to work out what your gauge needs resistance wise from the sender. This thread is valuable

https://www.theminif...p-sender-specs/

The thermostat issue may be due to a blanking sleeve being fitted or nothing, you will have to check it. It may be easier to remove the top hose from the housing than battling with the tstat housing as tney can be a real pain to remove and refit sometimes.

[DClarke1954]

 

It's best to first establish if the gauge is in fact working. I think I asked the question in one of your other threads - what brand / type temperature gauge are you running ?

 

 

That is the $64,000 question, who knows?

The car seems to be a "bitsa" in many regards.  Yes, the gauge is working (as I said above) if I ground the wire the gauge flips to the top of the scale.  If I put a variable potentiometer on there I could mess around with it to find the gauge's top/middle/lower values.   What gauge is it?  No idea, it's the one in the dash cluster, who made it?  No idea, what model is it?  No idea.

I suspect it is a common one for a MK3 mini 1,000 with a binnacle dash that has Speedo, Fuel & Temp Gauges Rev counter (L-R).  Who made it, what is it? ask me another.  LOL

It looks like this one, but not quite as smart/tidy.  

I am going to fit an 88° thermostat anyway (because for a road car that's the sensible thing to do), and then address the temp-gauge conundrum later.  Thanks for all the help folks.
Good to hear that cooking cyl's 3&4 if you have no thermostat is an "old-wives-tale".

Thanks for the help.

 

Edited by DClarke1954, Yesterday, 09:20 PM.

[DClarke1954]

You are working on 2 different issues, they may be vaguely related but not directly.
To establish what is going on with your temp gauge you should remove the sensor and see what it does when dunked in kettle hot water, mid range on the gauge is the aim here. You could also use a potentiometer or various resistors in place of the sender to work out what your gauge needs resistance wise from the sender. This thread is valuable

https://www.theminif...p-sender-specs/

The thermostat issue may be due to a blanking sleeve being fitted or nothing, you will have to check it. It may be easier to remove the top hose from the housing than battling with the tstat housing as tney can be a real pain to remove and refit sometimes.

Hi Dave,

 

So far I have dunked 2 different part number temp sensors in water and brought it to the boil to watch the resistance values change, so I know the sensors work. 

As you say, I don't know if the sensors are compatible with the binnacle temp gauge, but I know that the gauge works because if you earth it it goes to "H" and beyond. 
Good call on popping the hose and not the housing, I can stick my pinky in there and feel if there's a thermostat in place or just an empty space.

My fear was (having read a mini spares site that said "you will destroy cyls 3 & 4 if you run W/O a thermostat") that I would damage my engine without one.  But folks are saying that's just bunkum. 

[Ethel]

It's possible there's a broken thermostat that's not closing properly.

[Spider]

 

 

It's best to first establish if the gauge is in fact working. I think I asked the question in one of your other threads - what brand / type temperature gauge are you running ?

 

That is the $64,000 question, who knows?

 

OK thanks.

That's a factory fitted Smiths unit. A GTR101 Sender should be the correct one, but all I've tried / tested in recent years all make the gauge read hotter than is the case.

If it is all working properly, even without a thermostat, you should see some temperature read n the gauge.

If you have teflon or any other sealing tape on the sender, take it off. These don't seal on the thread, but on the tapered seat. Any tape you put on has a good chance of insulating the body of the sender from earth, rendering it useless. Before you disturb the sender, disconnect the wire from it, and measure the resistance from the terminal sender to an earth (not the body of the sender to start with), with the engine cold, you should be reading something around 350 - 400 ohms.

[timmy850]

Is it wired in using the gauge voltage stabiliser?

[68+86auto]

Is it wired in using the gauge voltage stabiliser?

Unless the PCB has been modified, it has to have the stabiliser fitted to work. Always good to make sure someone hasn't modified it though.

[DClarke1954]

Is it wired in using the gauge voltage stabiliser?

If the voltage stabiliser is a common element to all gauges and required for them to work then as the fuel gauge works properly I would say "Yes".  :)

[DClarke1954]

 

 

 

It's best to first establish if the gauge is in fact working. I think I asked the question in one of your other threads - what brand / type temperature gauge are you running ?

 

That is the $64,000 question, who knows?

 

OK thanks.

That's a factory fitted Smiths unit. A GTR101 Sender should be the correct one, but all I've tried / tested in recent years all make the gauge read hotter than is the case.

If it is all working properly, even without a thermostat, you should see some temperature read n the gauge.

If you have teflon or any other sealing tape on the sender, take it off. These don't seal on the thread, but on the tapered seat. Any tape you put on has a good chance of insulating the body of the sender from earth, rendering it useless. Before you disturb the sender, disconnect the wire from it, and measure the resistance from the terminal sender to an earth (not the body of the sender to start with), with the engine cold, you should be reading something around 350 - 400 ohms.

 

I understand its a 1-wire sender and uses the body as the return path, sealant on the threads should NOT be the issue if the sender does indeed mate with the matching conical surface in the casting.  

The conical surface should be all that is required for both sealing and earth-return path AFAIK, is that not so?  So the presence of sealant tape should not matter.  But I have a GTR101 arriving today so I will swap it out pronto.
Thanks for the help, I am getting there slowly.  :)

[Spider]

Tape or other sealants aren't needed or desired on the Sender, especially in light of the issues you are having.

 

<EDIT: Smiths also specifically state not to use tape or sealant;-

 

https://www.smiths-i...tal-diagram.pdf

 

Edited by Spider, Today, 10:30 AM.

[NLinPEN]

 

 

 

 

It's best to first establish if the gauge is in fact working. I think I asked the question in one of your other threads - what brand / type temperature gauge are you running ?

 

That is the $64,000 question, who knows?

 

OK thanks.

That's a factory fitted Smiths unit. A GTR101 Sender should be the correct one, but all I've tried / tested in recent years all make the gauge read hotter than is the case.

If it is all working properly, even without a thermostat, you should see some temperature read n the gauge.

If you have teflon or any other sealing tape on the sender, take it off. These don't seal on the thread, but on the tapered seat. Any tape you put on has a good chance of insulating the body of the sender from earth, rendering it useless. Before you disturb the sender, disconnect the wire from it, and measure the resistance from the terminal sender to an earth (not the body of the sender to start with), with the engine cold, you should be reading something around 350 - 400 ohms.

 

I understand its a 1-wire sender and uses the body as the return path, sealant on the threads should NOT be the issue if the sender does indeed mate with the matching conical surface in the casting.  

The conical surface should be all that is required for both sealing and earth-return path AFAIK, is that not so?  So the presence of sealant tape should not matter.  But I have a GTR101 arriving today so I will swap it out pronto.
Thanks for the help, I am getting there slowly.  :)

 

Slow down a bit, you are making too many assumptions. Do not assume that the sender is actually properly grounded. You seem to have a multi-meter? So you can measure resistance? If so, please disconnect the cable from the sender and measure the resistance from the sender's connector to the car ground. That's the only way to confirm, instead of assume, that the sender is having proper ground connection.