seized temp guage sender

[vegas602]

I need to replace a faulty temperature sender on my 1968 340, which added to the hard to get to position, it has well and truly seized in solid. Its had as much force applied as we dare, but simply cannot budge it and due to its location, soaking it with plusgas seems a waste of time. Has anyone any tips for removal please?

[PPV]

Is this in the thermostat housing? When I removed mine after removing the three screws I just kept on tapping the item with a little plus gas around the seal and eventually it came out. Take care though as the housing may be corroded and hence be fragile.
Best of luck.

[BookerME]

Did you manage to get it out OK?
Mine's on the underside of the inlet manifold and very, very difficult to access. I can just about get a spanner on it (for some reason it's an odd size too) - but it won't shift at all. It's really a silly, silly place to put it.

I'm a bit stuck as to what to do. It looks like the inlet manifold will have to come off so I can get it in a vice and maybe some heat on it. That means the water & air hoses, carbs, air filter etc. will all have to come off - not a job I'd relish really.

If you did replace it OK did you have any issues sourcing the correct part? I've read that there's different types with different resistance and therefore give different readings on the gauge.

Cheers, Mac.

[PatK]

Hi, there seems to be a little confusion here between the thermostat and the temperature sender. I have just managed to remove my temperature sender. It is of brass construction and located on the water rail just to the left of the thermostat housing. It does not have three screws and has it's own brass thread, I think that a 18mm ring spanner fitted mine, which was seized into the alloy water rail. I held the water rail firmly in a wooden jawed vice, close to the thermostat housing and applied a lot of heat from a gas blow gun. After approx five minutes I put the ring spanner on and thumped it with a dead blow hammer and then it slowly began to turn and eventually came off. I think that mine was the original ( 1965, 3.8l car ) and when I wire brushed and cleaned it up, it said " Smiths Industries " on it. Mine has a black material surrounding the brass terminal, but there are some out there with red material, which I think may give a different temperature reading, Ken Jenkins will probably know which is the right one. Hope that this helps. Patrick.

[BookerME]

Thanks Patrick, I was sort-of hoping you may have come up with a magic solution but you’ve confirmed my initial thoughts.
I’m also talking about the temperature sensor, not the thermostat or the automatic choke. It looks like I’ll also have to take the inlet manifold off and get it in a vice. I’d worked out it needed an 18mm spanner (the one I’m missing!) as none of my imperial spanners would fit and also it was larger than 17mm and less than 19mm. I just about got an adjustable on it after taking off the distributor cap but to no avail, it won’t budge.
Also, thanks for the advice on the colour. I’d read as much – though I won’t know what colour mine is until I get it off.
Mac.

[PPV]

Sorry, I miss read the heading and immediately thought of the sender for the auto choke which tends to fail readily. The temp gauge sender tends to be robust though and is fitted into the water rail. Hope you get it out Ok.

[BookerME]

Update – and success!

Sorted! Mine was just a duff electrical connection. I cleaned both the male and female connectors on the wire/sender unit under the inlet manifold, reconnected the wire, let the engine warm up and now the gauge works.
That saved me a considerable amount of unnecessary work!

And for info to others, in case you find yourself in this situation, I’ll also share what I found out.
The sender itself is a semi-conductor that responds to heat. As it warms up, its electrical resistance reduces, thus increasing the voltage of the circuit. Below is an extract from the manual that explains it.

Also, a retired engineer told me how to test the sender.
Remove the wire from the sender, turn on the ignition and touch the wire (briefly) to earth – done far easier with help from someone to watch the gauge. If the needle moves, it’s the sender – or in my case a duff electrical connection between the wire/sender due to corrosion.