Water temperature sender Marina 1275

[jammmorris]

Hello. Any advice would be very welcome. I've recently become the owner of a '66 convertible which has a Morris Marina 1275 engine. The engine number had corroded (it was literally white powder) so I'm not sure on which model Marina it was from but pretty sure it was an earlier model '71-75. It has a retro-fit water temperature gauge which has apparently never worked. As I was doing a coolant flush and re-fill I naively thought that if I swapped the water temperature sender for a new one and wired it to the gauge it would be OK. How wrong I was. I snipped the wire (capillary tube covered with coiled steel) and then undid the old temperature sender. The first bit came out OK but the back part was firmly wedged in the cylinder head with no way to take it out (see pic). In desperation I thought it might be possible to have a better view from the thermostat housing area but as soon as I tried to back off one of the 3 bolts it sheared off with very little force! Anyway, I tried the guys at ESM and they were very kind in giving advice. Apparently the only way to get the rest of the old temperature sender out is to take the head off and get it professionally drilled out as no swarf can get into the coolant system. And, the new water sender gauge I got from ANG apparently won't work with the gauge I have anyway if the old one was a capillary style (see pic of the new one I bought) so it was a total waste of time. By this point the air was blue and I put the old sender back together as best I could. I have run it and it doesn't leak so I'm going to leave it unless someone who may have done this exact thing before could advise me how to get the rest of the old one out and swap it for one that will work?! Or should I just leave the damn thing alone and hope it never leaks or overheats?!
As far as the thermostat sheared bolt, well that's another story. Unfortunately ESM only do the 3 replacement studs as per for Minors whereas the Marina is bolts. I've looked at ANG but their thermostat looks a little different from the one I have. Does anyone know if all the A series engines are the same in terms of thread size and the hole placement? Just trying to figure out getting a replacement set of bolts the correct size. As a temporary fix (which I was relatively pleased with) I drilled into the remainder of the bolt which was more or less flush with the thermostat housing. I tapped a 4mm thread and inserted a 4mm machine screw and tightened it down. It seems very solid and I'm leaving the other 2 well alone. I'm pretty sure it's not going to go anywhere but it would obviously be good to have it sorted eventually. I'm not sure what kind of pressure/force the thermostat housing will be under- perhaps someone has an opinion if my fix will be OK?
Please go easy on me with the comments and advice! This is my first post and I'm learning as I go and today was a nightmare!

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[philthehill]

Bad luck with the sender and bolts.
As regards the temp sender - give the remains of the sender in the head a good soak with Plus Gas not WD 40.
Leave it awhile and then wiggle the remains to free it off.
You should not have to drill out the remains. What is left is only pushed into the head and its retention is by the threaded ferrule which you have removed. You can get at the inner part of the capillary tube remains through the thermostat housing. Again a good soak with Plus Gas is a good idea. Knocking the remains via the thermostat hole should dislodge the capillary tube from its taper seat in the head.
The thread of the temp gauge sender in the head is 5/8" UNF.
Clean up the taper seat of the transmitter with a wire brush in a drill.
As regards the thermostat housing bolts - they should be studs not bolts. The ESM items are correct.
Again soak the bolts with Plus Gas and leave it awhile. Try and undo the bolts gently. If the heads do break off you may have to drill out the remains of the bolts and fit the correct studs. The thermostat stud threads in the head are 5/16" UNC. With 5/16" UNF threads at the other end for the nuts.
If you can get the bolts out run the next size dia drill through the thermostat housing holes and smear everything with Copper Ease grease before assy.
Loctite the studs in place as one or more of the studs goes into the water jacket of the head and can weep anti-freeze if not sealed.
You do need to replace that top hose and hose clips.
Replace the cork thermostat housing gasket with the latest paper type. Better sealing and does not distort.
https://www.ebay.co.uk/itm/251750460431 ... BM0OyAzOZh
If your engine block does not have the strengthening ribs then the engine is a early Marina pre 'A' Plus item. If the block does have the strengthening ribs then the engine is the later 'A' Plus engine. Basically the ribbing is the only difference between the early and late engines.
Good luck and come back on here if you need further advice.

[Bill_qaz]

Don't despair, good advice from Phil. If you have managed to drill through the broken bolt you could try an easy out in the drilled hole to remove the broken bolt after soaking with the plus gas.
I was changing my housing and half a stud came out with one of the nuts. unfortunately down the hole was not the remnants of the stud but the broken piece of tap that someone had snapped off the stud had been cut down and glued in.
I used a diamond tip hole saw to drill out the broken tap, the only thing that would drill it, then retapped the hole to original thread.

[jammmorris]

Wow, wasn't expecting such good advice so quickly. Thanks so much Phil and Bill. I'll definitely give that a go and hope I don't break anything else. If I remove the old temperature sender does that mean the Morris Marina replacement I bought will fit? If so do you know how I would then wire it up and which type of temperature gauge I actually need to make it work?
Thanks again, excellent advice.

[philthehill]

The replacement temp sender will fit the cylinder head but the transmitter may not suit the gauge. The gauge and transmitter should be matched.
The gauge currently fitted is capillary operated, the gauge matched to the new transmitter is electrically operated.
This is the gauge you need:-
https://www.merlinmotorsport.co.uk/p/sm ... 0-00-cb-wt
You will need the matching temp transmitter:-
https://www.merlinmotorsport.co.uk/p/sm ... 1-cb-ts-18
You will also need a voltage stabiliser:-
https://www.merlinmotorsport.co.uk/p/sm ... g-cb-vstab
And an adapter for the head:-
https://www.merlinmotorsport.co.uk/p/th ... dp-5-8unfa

[jammmorris]

Thanks Phil, that's great.
I came across this on ESM, would this work by any chance? https://www.morrisminorspares.com/elect ... h-p1238407

Cheers

[philthehill]

Yes - provided your vehicle has been converted to negative earth.

[jammmorris]

Thank you- one last question! How do I find out if it's been converted to negative earth please? This is a photo of the engine bay in case that helps (also can you tell the engine model from this image?).
Cheers

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[philthehill]

Look at the battery. If the Negative (marked with a - ) lead is attached to the body it is Negative earth.
I note that you have an alternator fitted. Most alternators are negative earth therefore I am certain you have a Negative earth electrical system already fitted.

[jammmorris]

You're a legend. Thanks so much.

[Bill_qaz]

Think you're correct Phil if you zoom in the battery is marked + and - and the + goes to starter side. His neg is to battery carrier.

[jammmorris]

Hi everyone. Thanks for all your help so far Phil & Bill. I've ordered the parts for the thermostat housing, just waiting for them to turn up.
I've trawled the MMOC forum about how to correctly wire up the water temperature gauge but the only post that sounded like it was close to what I needed has been removed so I'm afraid I need your help again! Would anyone be able to help advise me please (I didn't find the wiring diagram it came with very informative)? I ordered this from ESM: https://www.morrisminorspares.com/elect ... h-p1238407
I was told that I run one wire from the water temperature sender in the cylinder head to one of the terminals on the back of the gauge (not sure which terminal- does it matter)? Then I take a live feed to the other terminal. Might sound silly but where do I take the live feed from? I've read something about a voltage stabiliser from the speedo? Is there a spare terminal for this or do I take the feed from elsewhere? Just don't want to do it wrong and short something out. Then, there's the bulb that's in the back of the gauge. How does that get wired in?
On a separate note, as I originally ordered the water temp sender from ANG (before I found out the difference between the capillary and electrical versions) I was told by ANG that my engine is probably from a 1275 Midget because it has a capillary sender. I'm a bit confused as the previous owner definitely said a Marina (as were the wheels, brakes and axles)- is it possible to ascertain which engine I have from the image above?
Thanks again for your help, best wishes.
Andy

[svenedin]

Sorry to hear about these mishaps. The thermostat housing can be a real nuisance. It’s made of aluminium alloy but the block Is cast iron and the studs are steel. You didn’t do anything wrong, it’s just an unfortunate design. In the past I have had to completely destroy a thermostat housing totally seized on the studs. It will be good when you have it sorted as you do need to be able to get the housing off to change the thermostat. After all this trouble fit a new thermostat to be sure! Some owners swap the thermostat in Spring and Autumn so that in Winter they have a hotter heater and an engine that warms up better.

Stephen

[Bill_qaz]

I can't help with gauge wire as mines a capillary but to illuminate the gauge you wire the bulb to one of the wires that goes to the illumination bulbs of your speedo. Also the body of the gauge has to have earth, I ran a wire from the nut holding the gauge to the body.
Then when you turn your light on the gauge will illuminate.

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[StillGotMy1stCar]

On a separate note, as I originally ordered the water temp sender from ANG (before I found out the difference between the capillary and electrical versions) I was told by ANG that my engine is probably from a 1275 Midget because it has a capillary sender. I'm a bit confused as the previous owner definitely said a Marina (as were the wheels, brakes and axles)- is it possible to ascertain which engine I have from the image above?
Thanks again for your help, best wishes.
Andy

Difficult to make out in your photo. The Marina has the oil filter high up to the rear beside the distributor, screwed directly in to the block. The Midget oil filter is lower down below the alternator on a separate filter head assembly.

Regards John

[philthehill]

Your engine is a 1275cc Marina/Ital unit.
If you enlarge the photo of your engine bay the oil filter can be seen to the O/S rear of the engine.
The Marina/Ital engine was fitted with a electrical water temp transmitter/gauge not the capillary type.
You may find that the thermostat housing is not suitable as the angle of the top hose is different when a Marina 940 head is installed.
Have a read of this thread:-
viewtopic.php?t=71471

[jammmorris]

Thanks for the information, good to know what engine I have! Getting a bit confused- I'm hoping to keep the current housing as it seems hard to match it. Will the 5/16" replacement studs/nuts coming from ESM still be OK for a straight swap? I've ordered the paper gasket from ebay that you recommended Phil. I've got the PG spray ready!
Still a bit unsure about where to get the live feed from for the gauge? Or are you saying that might not work with my engine? Sorry, new to all this. Thanks very much.

[philthehill]

The studs will be a straight swop with the bolts already installed. Drill the holes in the housing to 3/8" and smear the studs with Copper Ease grease. Smear the new paper gasket with grease as well. Do not forget to cover the stud threads that go into the head with Loctite.
For a live feed for the gauge take a wire off the fuse box, the one that is live when the ignition is switched on.
The gauge will work with what you have purchased.
The wiring should be - fuse box ignition live - wire to gauge - wire to transmitter - earth return to battery.
Remember you have negative earth - so if the gauge terminal is marked negative that is the connection/wire to the transmitter which is fitted in the head in place of the capillary tube.

[jammmorris]

Ah, great thanks. Will give that a go!
Cheers again.
Andy