Over temperature warning

[jonbarrett]

As you will see from my other thread my water temperature gauge has failed and I am trying to fix it. If I was driving the car and the cooling system started to fail will I get any other dashboard warnings like a big red flashing light before I do any damage.

I wondered whether the engine ECU would illuminate the engine warning light if the temperature got too high.

[FarmyardPants]

I don't think so. I got 120c on the gauge, ie the temp needle went on a foray into the oil pressure dial, when my rad sprung a leak. Nothing lit up or beeped, although a brown marking appeared

[marcus1970]

jonbarrett said:

As you will see from my other thread my water temperature gauge has failed and I am trying to fix it. If I was driving the car and the cooling system started to fail will I get any other dashboard warnings like a big red flashing light before I do any damage.

I wondered whether the engine ECU would illuminate the engine warning light if the temperature got too high.

Don't know, but if you have the laptop plugged in all the time the temp sender will show the exact temp on the diagnostics software - to 1/10 of a degree.

MB

[hugepiece]

I suppose you could always bi-wire the fans straight from the battery so you can manually switch them on for some peace of mind, then you could potentially leave them on all the time. I know it's not a visible warning or anything but it's some added protection just in case??

[marcus1970]

hugepiece said:

I suppose you could always bi-wire the fans straight from the battery so you can manually switch them on for some peace of mind, then you could potentially leave them on all the time. I know it's not a visible warning or anything but it's some added protection just in case??

If you take the temp sensor connector apart, both of the fans come on automatically, as a fail safe against the unit being faulty.

MB

[grass widow]

Our temp gauge is currently reading 20ish degrees above its true temp, we had it on the computer and it read 116 on the dial but it was only at 91. The fans kicked in at 92 and the second fan kicked in at 105, and after some revving we got a vent of steam from under the bonnet.

I asked how we would know if it was overheating for real and I was told we would have two needles in the oil temp, you would probably get a vent of steam out of the water reservoir and the heater would go cold.

[longbow]

grass widow said:

I asked how we would know if it was overheating for real and I was told we would have two needles in the oil temp, you would probably get a vent of steam out of the water reservoir and the heater would go cold.

By that time the damage will probably be done.

[hugepiece]

marcus1970 said:

hugepiece said:

I suppose you could always bi-wire the fans straight from the battery so you can manually switch them on for some peace of mind, then you could potentially leave them on all the time. I know it's not a visible warning or anything but it's some added protection just in case??

If you take the temp sensor connector apart, both of the fans come on automatically, as a fail safe against the unit being faulty.

MB

I think you can only do this once the car has started so probably not that practical. I'm sure from memory that if you try and start the car with this disconnected the MIL light comes on and the car either wont start or runs like a dog.

[Far Eastender]

The analog dials are hopeless. My car was always in the 105-110 range in traffic. When I fitted a digital dial and new temp sensor, it's now only in the 95-98 range and normally at 80C.

Edited by Far Eastender on Wednesday 27th June 13:10

[Steve_T]

hugepiece said:

marcus1970 said:

hugepiece said:

I suppose you could always bi-wire the fans straight from the battery so you can manually switch them on for some peace of mind, then you could potentially leave them on all the time. I know it's not a visible warning or anything but it's some added protection just in case??

If you take the temp sensor connector apart, both of the fans come on automatically, as a fail safe against the unit being faulty.

MB

I think you can only do this once the car has started so probably not that practical. I'm sure from memory that if you try and start the car with this disconnected the MIL light comes on and the car either wont start or runs like a dog.

If you unplug the temp sender, the car will run, but the ECU assumes the engine cold and fuels accordingly, which can kill your cats when the engine is warm. If you have no cats, you'll get awful fuel consumption. I'm not sure if there's a risk of washing the cylinder bores - I've only heard of this from an injector sticking open - so I guess not. Apparently the better way to jury rig things is to supply 12v in place of the input from the sender (this was the advice given to one of the Surrey guys by Andy at APM while we were away when his temp sender packed up). From this I assume that the voltage from the sender increases with temperature and the ECU reads 12v as engine being too hot and switching the fans on, avoiding overly rich fueling.

Steve.

Edited by Steve_T on Wednesday 27th June 13:21

[marcus1970]

Steve_T said:

hugepiece said:

marcus1970 said:

hugepiece said:

I suppose you could always bi-wire the fans straight from the battery so you can manually switch them on for some peace of mind, then you could potentially leave them on all the time. I know it's not a visible warning or anything but it's some added protection just in case??

If you take the temp sensor connector apart, both of the fans come on automatically, as a fail safe against the unit being faulty.

MB

I think you can only do this once the car has started so probably not that practical. I'm sure from memory that if you try and start the car with this disconnected the MIL light comes on and the car either wont start or runs like a dog.

If you unplug the temp sender, the car will run, but the ECU assumes the engine cold and fuels accordingly, which can kill your cats when the engine is warm. If you have no cats, you'll get awful fuel consumption. I'm not sure if there's a risk of washing the cylinder bores - I've only heard of this from an injector sticking open - so I guess not. Apparently the better way to jury rig things is to supply 12v in place of the input from the sender (this was the advice given to one of the Surrey guys by Andy at APM while we were away when his temp sender packed up). From this I assume that the voltage from the sender increases with temperature and the ECU reads 12v as engine being too hot and switching the fans on, avoiding overly rich fueling.

Steve.

Edited by Steve_T on Wednesday 27th June 13:21

If you unplug the temp sender I thought that the ECU assumes the car hot (ie doesn't want the car to cook) and so turns both the fans on?

MB

[Steve_T]

marcus1970 said:

Steve_T said:

hugepiece said:

marcus1970 said:

hugepiece said:

I suppose you could always bi-wire the fans straight from the battery so you can manually switch them on for some peace of mind, then you could potentially leave them on all the time. I know it's not a visible warning or anything but it's some added protection just in case??

If you take the temp sensor connector apart, both of the fans come on automatically, as a fail safe against the unit being faulty.

MB

I think you can only do this once the car has started so probably not that practical. I'm sure from memory that if you try and start the car with this disconnected the MIL light comes on and the car either wont start or runs like a dog.

If you unplug the temp sender, the car will run, but the ECU assumes the engine cold and fuels accordingly, which can kill your cats when the engine is warm. If you have no cats, you'll get awful fuel consumption. I'm not sure if there's a risk of washing the cylinder bores - I've only heard of this from an injector sticking open - so I guess not. Apparently the better way to jury rig things is to supply 12v in place of the input from the sender (this was the advice given to one of the Surrey guys by Andy at APM while we were away when his temp sender packed up). From this I assume that the voltage from the sender increases with temperature and the ECU reads 12v as engine being too hot and switching the fans on, avoiding overly rich fueling.

Steve.

Edited by Steve_T on Wednesday 27th June 13:21

If you unplug the temp sender I thought that the ECU assumes the car hot (ie doesn't want the car to cook) and so turns both the fans on?

MB

I distinctly remember the comment about wiring the sender connection to 12v, rather than leaving it open circuit, to avoid damage to the cats. It would obviously be worth confirming this with Andy, to be sure that I've remembered correctly and not missed out an important detail.

If you want to switch the fans on, you could go another way I suppose. The ECU switches the fans on by grounding out the earth side of the relay coils. You could leave the a sender connected and ground out the fan relays with alternative wiring, although I can't remember from the wiring loom diagrams how and where in the loom to do this.

Steve.

Steve.