Removing temperature sender

[Dave O]

I’m completely new to this forum and relatively novice so go easy! I’m trying to get my 1978 spitfire 1500 back to a driveable condition (it’s last MOT was 1987 and it sat in dry storage for a very long time). Have got the engine running but I noticed the temp gauge staying at cold despite running the engine for 10-15 minutes and decided to renew the sender having checked the cable  to temp gauge was fine. Thought it would be a simple replacement but having drained out the coolant, cannot get the old sender to screw out. It appears to have completely seized. I’ve tried using penetrant spray (WD40specialist product), Crack It release spray and even tried EvapoRust soaked in tissue and clamped onto the sender inside and out for 24 hrs. I’m worried I’ve now rounded the hexagonal nut and caused a bit of damage using grips. It’s made of brass and I can see small bits of brass coming off whenever I try to undo it with my 18mm socket. Have also tried using a manual impact wrench (whacked with a hammer a few times). Should I now be investing in a propane torch (never used one) to heat it, and how can I grip the hex nut now it’s rounded? Any advice or tips welcome. PS have supplied photos.

[Josef]

Path of least resistance at this point might be to just replace the water pump housing. One on eBay, or breakers such as Spitfire Graveyard and Spitbitz are worth a call https://www.ebay.co.uk/itm/225089997171?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=Ksh36BaPRvq&sssrc=4429486&ssuid=en_MztWYTyu&var=&widget_ver=artemis&media=COPY

If you don’t want to go that route yet, taking the housing off and gripping the sender in a vice is worth a try. Also possible to completely destroy it by drilling it out and using a tap to clean the brass remains out the threads, though there’s a risk of damaging the threads in the casting, or them being so rusted to be of no use.

[Peter Truman]

It should give being an all brass sender screwed into a cast iron water pump body. Original Equipment Smiths senders as fitted to my Vitesse had a steel sender body with crimped on internal brass bulb, now they were difficult, they rusted in.

Try a small set of Stilsens, or Footprint wrench's, I have one of each around 7in long that would be great on that they would lock on and just bite tighter as you heaved, or maybe a Mole wrench, but that might slip

[Pete Lewis]

its a good case to have used a 6 hex not a bi hex socket then not so easy to round off the corners 

maybe one of the multifit one from many suppliers even amazon one  size fits all sockets will grip ???

 

[Colin Lindsay]

File two opposing flats down to the next spanner size, Imperial or Metric, and that should give a better grip with a spanner, which you can whack with a soft-faced mallet until the sensor loosens. 

[DerekS]

Another old trick is to try tightening the offending article, very carefully and just a smidgen, you dont want to shear the top off. If it moves you've broken the grip and can ease it by loosening/ tightening till it frees up. Doesn't work every time but something to remember. You'll get it!

Derek.

[chrishawley]

Had a comparable instance yesterday removing the brake pipe union from a caliper. Pipe sheared off at the base and nut rounded off.

In this instance I got a result by driving a ring spanner onto the nut - what started off as a 7/16 A/F nut had a 10mm persuaded onto it with hammer blows. Spanner was scrap afterwards but a sacrifice worth making.

Then heated the area using an ordinary little butane 'decorators's'  torch. Well cooked. - about a minute. Then with an extension tube over the spanner applying lots of torque but aiming for minimal movement in both directions. Once it 'cracked' it was still a fight but eventually got there by reheating and working backwards and forwards with an increasing range of movement.

Heating things, if the part in question is ammenable to be being heated, really does work. And I guess nobody likes sacrificing tools to a job - but in this case £3 -5 for a new spanner to save a caliper worth £££s seemed worth it

[Wagger]

I use my 'Metrinch' ring spanners for this sort of thing. They grip on the flats, not the corners. They were a leaving present year 2000 and are very useful for rounded nuts and bolts.

[GrahamB]

I have found these effective but the price seems to have increased significantly since I purchased a set.

[Dick Twitchen]

Second Graham's recommendation.  Found them invaluable restoring the GT6 and working on a variety of old Land Rovers.

Dick

[johny]

Im a great believer in penetrating oil (dont think which one matters too much) but its got to be repeatedly applied for days if not weeks before attempting the undoing. Squirting it on and trying straight away is not using its full potential....

[Dave O]

Thanks for all the replies so far - some great ideas. I’ll try a few out and let you know…

[Graham C]

Hello Dave

Can suggest you stop removing the sender and test it. The sender is a very simple device, two thermocouple disc at the bottom of the brass housing held in place with a spring connected to the terminal which is isolated from the housing by a a plastic insert.

You should be able too apply heat to the sender, less than 87c and with a multi meter attached to the terminal and the negative to the engine a DC voltage should be read.

Hopefully this will confirm if the sender is working or not.

If working then the problem is elsewhere.

Graham

[Colin Lindsay]

Graham's reply reminds me of the other test, earth the sensor cable to the block and see if the gauge goes to full. That will spot a duff gauge, and the sender could be ok?

[Dave O]

Thanks Graham and Colin. When I get a chance I will test it. Out of interest what would you suggest for how to apply heat to the sensor?

It did occur to me too that maybe the sensor is okay all along. I was making a presumption based on fact the temp gauge remained at 0 after running the engine for about 10-15 minutes. I had tested the cable and cleaned the contacts and these seemed fine. But later when I took off the thermostat housing there was no thermostat! Not sure if this was normal for 1978 spitfires or if someone has removed this sometime in the past. But I presume if no thermostat it may have meant the engine would not heat up so quickly and maybe I just didn’t run it for long enough…

Anyway because I’ve fairly butchered the sensor in trying to remove it I feel inclined now to replace it with a new one - I have a set of the Irwin bolt grips previously suggested that came through the post today - I’ll give these a go after a few days soaking in penetrating oils and report back.

[Pete Lewis]

as the 1500 is in some start of emmision controls of the day should have a 88C thermostat fitted (all others are 82C)    being leaner it runs hotter 

sorry who ever took  it out is on  a fools errand .

i agree with all the hassle and rounded corners its as well you persevere to a change it 

needs a GTR108  generic sender 

Pete

Edited September 11, 2023 by Pete Lewis

[johny]

7 hours ago, Dave O said:

But later when I took off the thermostat housing there was no thermostat! Not sure if this was normal for 1978 spitfires or if someone has removed this sometime in the past. But I presume if no thermostat it may have meant the engine would not heat up so quickly and maybe I just didn’t run it for long enough…

It could be that it failed closed and never got replaced. However more likely is that it was removed in an attempt to improve cooling because the engine runs hot. This doesnt help and as you say just extends warm up time🙁

[Graham C]

If you wish to continue removing the sensor when removed, stand it in boiling water and connect multi meter to the terminal and housing. This will just confirm if the sensor was working or not and if not then you still have a problem.

Good luck.

Graham

[Dave O]

Quick update - it’s out!

The bolt grips worked a treat! First tried the largest one which just ate away more brass but then hammered on the next down size and the torque bar did the rest.

Many thanks to you all I’m really pleased I joined this forum!

For the record I tested the gauge as recommended and it works. Haven’t a clue about the sender though it was showing volt readings all over the place even before I applied any heat.

New sender looks like the right one so hopefully it’ll all work

I guess now the challenge is cleaning up those threads - squirt of degreaser and a wire brush I suppose…

Cheers everyone 

[Pete Lewis]

and while you in there  make sure your new thermostat has a jiggle pin in its rim to aid filling /air escape  if its not got one a small drilled hole 2/3mm will work 

too many are sold with this important bleed omitted  and you will get refilling problems and air locks 

pete

 

[daverclasper]

On 11/09/2023 at 07:32, Pete Lewis said:

as the 1500 is in some start of emmision controls of the day should have a 88C thermostat fitted (all others are 82C)    being leaner it runs hotter 

 

Hi Pete. Something basic, that I'm not getting.  If an engine is running hotter, then I would have assumed that the stat opens at the lower (82C temp)?

[Pete Lewis]

thermostats modulate  thats they open and close as cooler water enters the head it closes and reopens when the setting is reached 

leaner engines of the 70s mostly run hotter 88c than earlier engines in uk are 82c  all pretty standard stuff of the era

if you look in the rad header /filler on a hot engine you will see the flow across the rad tubes flow and ebb as the stat controls the temperature 

its not just case of open or shut  but anywhere in  between 

Pete

[johny]

2 hours ago, daverclasper said:

Hi Pete. Something basic, that I'm not getting.  If an engine is running hotter, then I would have assumed that the stat opens at the lower (82C temp)?

I think also that as time went on they wanted the engines to run hotter to improve emissions and of course the easiest way to do this is use a thermostat that modulates at a higher point. I believe with modern engines this is now so critical that electronic controls are used to keep engine temperature within the closest possible limits...

[daverclasper]

Thanks chaps. So I was correct in assuming that the lower the temp the stat opens, the cooler the engine will run. Was wondering if its worth it, to check mine is the lower one, as do get fuel vapour problems if stuck in traffic, on very hot days in Vitesse.

Would this make a difference?

 

 

[johny]

Unfortunately its not as simple as that Dave as you can have no thermostat but if your rad is knackered or too small, airflow restricted, cooling system not clean or engine not running right and producing excess heat your car will still run hot. However yes IF you have excess cooling capacity in your system (unlikely in a standard 50 year old Triumph) a lower setting thermostat will keep the temperature down. Be aware though this is more likely to happen on days when the ambient air temperature is lower (winter) as of course thats when your cooling system has increased heat transfer capacity and the thermostat can start to close to reduce flow through the radiator....