4.108 Engine Temperature Sender

[SimonV]

The temperature sender that screws into the top of the head on my Perkins 4.108 is cactus. It has been sending a high reading for a while and now sends the gauge to full hot as soon as the ignition is turned on and I was able to get it to work for a bit if I tapped it with a hammer. I have tried to remove it (brass in cast iron head) but it won't budge. I have tried it with the engine cold and hot, soaked it in WD40 still won't budge. I'm concerned if I put too much pressure on it will snap off quicker than a Jewish foreskin. If someone tells me its a left hand thread I'll cry.

[gordwedman]

No, it shouldn't be left hand thread. Since you are going to replace it no harm done heating it up really hot with a propane torch. Try turning while still hot. Brass is not too sturdy as you say so there is a chane it might snap if you use too big a wrench. Then you have a hole that needs plugging...

[cburger]

You might give this a try: PB Penetrating Catalyst

[BruceS]

Simon that sender unit is around 1" so I'd think you could put a fair bit of pressure on it. If you have the right sized long socket or tube spanner so that it has equal pressure all around it, it should give I'd think.
Needless to say I wouldn't be using an open ender!!!....

[SimonV]

Originally Posted by BruceS

Simon that sender unit is around 1" so I'd think you could put a fair bit of pressure on it. If you have the right sized long socket or tube spanner so that it has equal pressure all around it, it should give I'd think.
Needless to say I wouldn't be using an open ender!!!....

Now I am back at a marina in civilization I will risk putting in some extra effort. After the Australia Day weekend.

[GILow]

Simon, if it won't come out it may be simpler to fit the new sensor inline in the cooling system elsewhere. (Choosing a place where you get an accurate reading of course.). What you are experiencing used to be a common problem with old European alloy head engines and we found it was sometimes simpler to fit a new sensor in the radiator hose immediately after the thermostat. The reading was practically the same as the reading from the thermostat housing and it saved the risk of shattering the thermo housing itself. (which happened to a few engines over time. )

Good luck.

Matt

[donradcliffe]

A 6 point combination wrench and a 2 pound hammer should do the job.

[GILow]

Originally Posted by donradcliffe

A 6 point combination wrench and a 2 pound hammer should do the job.

Ha, ha. Strangely enough, this combo is often referred to as "The American Screwdriver" in workshops in Australia.

I hope that temperature sensor is threaded into something strong.

[SimonV]

Originally Posted by donradcliffe

A 6 point combination wrench and a 2 pound hammer should do the job.

I was about to ask what that was. Now I know it's a ring spanner. But there is no room to swing a hammer abd I will be standing on my head.
Matt. The sender is tapped into the rear of the head (cast iron) and hard up against an injector. If I bust if off it will mean pulling the head.

[donradcliffe]

A shot of PB Blaster a day for 4-5 days should loosen it right up. I you still can't get it to move, hand the spanner to some young ocker and tell him its easy.

[BruceS]

OK you made me go check. That one on mine has been a problem some time in the past and has been drilled and tapped and a stainless bolt inserted through the centre of it. The new sender has been put in almost alongside the thermostat housing near the heat exchanger. (other end of the head) Made you day? & good luck!!

[GILow]

Sounds like this could be a common problem for that engine just like the Renault engines we used to rally. We ended up leaving the old sender in place. Let us know how it goes, I've got my fingers crossed for you. Nothing like the sickening feeling of a spanner suddenly freewheeling TOO easily to make you wonder if there was another way of fixing something.

[GILow]

I suppose if the engine is raw water cooled, leaving the old sender in place would not be an option? I guess it would corrode eventually. Leaving in place was not problem with engines full of anti corrosives such as we used on the Renaults.

[SimonV]

Bruces. Huston we have a problem. The location you mention at the front of the engine where your present sender is located is all ready in use by another pipe which has a low water/over heat alarm fitted. The fact your old one is still in place but modified to seal, concerns me even more that mine may twist off. At least now I may have a plan. If I do need to drill and tap whats left, it should only be fine brass swarf and I can't see that being an issue in the closed fresh water system.

[cburger]

Originally Posted by donradcliffe

A shot of PB Blaster a day for 4-5 days should loosen it right up. I you still can't get it to move, hand the spanner to some young ocker and tell him its easy.

Second this, spray the base of the sender over a period of several days
and give it a try, the product is made for this exact application.