Coolant Level Warning Light Problem...

[Rob Thomson 6]

Hello chaps,

 

There's something wrong with my coolant level warning light. It comes on only at high revs, only when the engine's under load, but not every time I drive the car. When this happens it comes on at about 4k rpm and then goes out as soon as I lift-off/dip-the-clutch to change gear.

 

Does anyone understand how it works? Mine's the Phase 2 black header tank, and my memory of the sender is that it's just a couple of metal prongs that stick up into the coolant. Presumably there must be a device between the sender and the warning light that deduces the coolant level from the resistance between those two prongs?

 

Any ideas...? It's starting to get on my wick.

 

Before you ask... it's got loads of water in it!

 

Thanks, Rob.

[DrSarty 90 1 Cars]

There was a really interesting thread about 'how it works' recently, started by Damir IIRC. It all revolves around a green thing.

 

In your case, I suspect it's a conspiracy.

 

 

 

 

 

 

[jimistdt 1]

It works by means of a reed contact, there was an interesting thread on here by Damir all about it, it was initially suspected that magic was involved, turns out its magnets, sometimes I believe the sensor can be affected by electrical currents close to the sender....(interference was the word I was looking for there)

[Grim.Badger 15]

The older phase 1 tanks had two types of sensors; one that was prongs but another that was a float inside a tube, the float could get jammed up with silt and give false readings. I'm not sure if phase two cars also had two types of sensor but this is possible. Another potential problem could be corrosion on the prongs, they can be cleaned up with vinegar and a quick rub down.

As far as I know the system works because when the coolant level drops the water is no longer completing the circuit and the dash light comes on

[GLPoomobile 958]

Rob has a Ph2, so it won't have a reed switch, or a "green thingy". Like he said, two prings that stick up in to the tank.

 

I don't know how it works, but I've read loads of times that it is interference from the ignition components. Anthony or Graham (forget which) usually talk about this and say you need to move the sensor wiring or the ignition wiring (presumably the amp wiring, since the coil is no-where near on a Ph2) as far apart as possible.

[chris-stdt 0]

Mine comes on at 3k and like yours gos off when you lift off

 

Its only been doing this since the headgasket went and its not low on water it just pressurerises the system abit ??

[jackherer 543]

Rob has a Ph2, so it won't have a reed switch, or a "green thingy". Like he said, two prings that stick up in to the tank.

 

I don't know how it works, but I've read loads of times that it is interference from the ignition components. Anthony or Graham (forget which) usually talk about this and say you need to move the sensor wiring or the ignition wiring (presumably the amp wiring, since the coil is no-where near on a Ph2) as far apart as possible.

 

Its interference from the HT leads, usually when they aren't clipped into the holder on the cam cover. If they are routed correctly and its still doing it the leads may be faulty, even if the engine is still running fine they can still be leaking RF.

[Rob Thomson 6]

Hello chaps,

 

I'd forgotten I'd posted this, going senile at the age of 29 and three-quarters. Not good...

 

Ok, I'll check the ignition. In my mind's eye the HT from the coil to the dizzy swings around somewhere near the sender so I'll try moving that out of the way. I also suspect the leads are getting old, it misfires randomly ever now and then in a way that reminds me of my old Mi16 when the leads were f*cked.

 

Chris-stdt, I've been worrying about head-gasket problems for a while now but am now fairly convinced that I don't. That's one of the reasons this light's getting on my tits because whenever I see it come on the first thing I think is that it's just blown all its water out through its breather....

 

Anyway, thanks chaps, great service as always.

 

Rob.