Header Tank Knocking

[DMT]

I have been irritated with the noise of the float/switch in my Header Tank banging as it hits it top limit when the car is knocked. When driving I don't hear it.

I had set it up so when the water level drops the switch closes and puts the warning light on.

I wanted to reverse the orientation of the switch so it is closed when the water is high enough so won't bang.

When working out the wiring I realise this new option would need a relay and would make it fail safe, as at the moment if the level switch fails, or the connection to the switch and earth is broken then the light won't come on.

Using the level switch to energise a relay and hold a it's N/C contact open to keep the light off is a better way?

The only negatives I can think of are, the cost of a relay, and that the water level when the switch opens now, will be lower than the level that the switch closed before, to say there was a problem.

I am thinking of using an ON delay relay, this would give a bulb check before energising.

What do you think?

Dave

[NeilR]

Float switches tend to use 'reed relays'.
They don't like the higher current of a relay / back emf's from relay coils, it will weld the contacts closed.

[DMT]

I am planning to use an electronic programmable delay unit. Do you think this would be OK?

[Wheelz]

I am planning to use an electronic programmable delay unit. Do you think this would be OK?

Yes.

[DMT]

Ta

[NeilR]

Yep, I would think it would be ok.

[sujitroy]

Be careful with a delay switch. Maybe the slightest delay could be too late.

[wilf]

Dave - what is jostling your car so much that it sends coolant inside the header tank surging enough to move the float switch? Would it be possible/easier to arrange a "soft stop" for the float - admittedly getting something like a small piece of foam or soft rubber glued in place, surrounded by coolant could be fun.

[DMT]

The noise is only when working on the car, but this investigation has highlighted the system is not fail-safe, and has no way of testing the bulb.

I thought of a soft stop, but it is not easy with the way the float is made, and if it came loose and went into the pump etc......

I believe the failsafe and bulb check out-weigh the delayed warning.

Thanks for the views Gents.

Dave

[richardthestag]

I do not know what type of tank nor level switch that you are using but do have a question.

If the switch is banging the top of the tank, how can there be enough of a head above the maximum coolant level for air into which the coolant needs to expand?

I share also the concern about the delay units. very useful to stop the ubiquitous flickering low fuel light but do you really need to wait "10 seconds" before you find out a hose has blown and all your coolant is in lane 3 of the m4?

As for bulb test you could add a switch under the dash to give the bulb a temporary route to earth for testing....

[DMT]

Hi Richard

The banging is the switch hitting it's end of travel not the top of the tank. I thought of putting something to soften the top limit of travel but was worried it would come loose and block somewhere.

The delay stops the relay energising on initial power up (ignition on), which means the light is on until it times out. I was thinking the light on for 2 secs was all I needed and not be annoying.

When the switch opens with low water the relay immediately drops off and the N/C contact brings the light on.

You are quite right I did buy the delay to stop the low fuel light from flickering, but thought this was a better idea. I might have to buy another if this works?

Thanks for all the thoughts. if I have an answer for all of them it might be worth doing.

Dave

[jbuckl]

Is this thread about fuel or coolant or both? Both seem to feature??

[DMT]

This is just about the header tank.

I purchased the electronic timer for the fuel light flashing problem but will use it for the coolant level mod and buy another for the fuel.