I was driving my 1973 series 1 4.2 the other day. Everything was running smooth when I noticed the temperature gague all of a sudden was reading zero. I stopped the car and looked under the hood.

The only thing I noticed was that the expansion tank has a seemingly very small leak (small drops but no obvious flow) from the seam underneath. Anyway there was still fluid in the tank, and I topped up untill the tank was about half full.

Then I continued driving home for another 10 minutes, and the gague was fluctuating slowly between zero and normal. Mostly around zero.

Once the engine had cooled off completely I opened up the filler cap on the engine. The fluid level was about 5 centimeters below the cap. See the attached picture.

Now to my questions:
1. What can the cause of the abnormal gauge reading be?
2. Is the coolant fluid level in the engine block normal? If not, where should it be?
3. Is it safe to drive the car.

 

Either a wonky temp sending unit, loose wire at unit, or possibly gauge fault.

 

Welcome to the forum.

That filler spout on top of the engne is meant to be 100% full.

The header tank on the LH inner guard is where the expansion/contraction takes place.

With a known leak, it will always give grief. That needs repairing before any more diagnosis is done, simple.

The temp sensor is under the inlet manifold, basically behind the front carby, and has a single Green wire attac

As said, the wire/connector/sensor may be the issue, but IF that sensor is NOT making contact with coolant it will NOT give a reading, as it is designed to sense fluid, NOT vapour/steam/hot air.

Remove that sensor wire, ign ON, earth that wire, and note the dash gauge going full scale, which is a usual indication of a faulty sensor unit, about $10.

 

Thanks, and thanks for the advice.

I have been lurking around this forum for some time. Been wanting to buy an XJ S1/2 for 10+ years. Last year the oppertunity to buy an immaculate series 1 came up, and now it is mine. It has been more or less completely restored over the last 19 years, including a completely rebuilt engine. However the car has been driven no more than 7000 km during those years. I guess I will be seeing some recommissioning issues for the time coming.

Anyway, a new expansion tank has been ordered. Once fitted, to what level shall the tank be filled? I will refill the engine block to the top of the filler cap anyway as advised above.

 

Good.

About half way.

There is no hard and fast level.

Those 2 hoses on the edge of that snap look a tad tired and swollen?, so maybe address them whilst you wait for that tank.

Where do you call home???, since different markets have different items all over the car.

Add your abode through the "User CP".

 

It's been a while so thought I would update on the progress. Warning, Wall of Text, though.

July last year I followed all of the above advices. The temperature gauge was confirmed ok. The hoses were replaced with new ones. A new "original" expansion tank was ordered from SNG Barratt. (The old tank had definitely seen better days.) The engine block was filled to the top and the expansion tank about half way with coolant.










Then I drove the car without issues a few km. After sitting for about 45 minutes I fired the car up again. A huge cloud of white smoke came out of the exhaust. The temperature gauge didn't give a proper reading. Shut the car down and didn't drive it anymore.

This was a bit worrying since pretty much exactly the same thing had happened a few months earlier and less than 1000 km ago. The only difference this time was that I noticed a small amount of coolant penetrating at one of the cylinder studs/acorn nuts. The first time this happened the headgasket was replaced by one of the most reputable Jaguar workshops around here.





However at that time there were no obvious signs of the head gasket being blown, and both the head and engine block were measured to be completely straight. Could there perhaps have been some other cause behind the coolant leak both the first and second time? Also remember that the engine was completely rebuilt less than 8000 km (but many years) ago.

I had the car flat bedded back to the workshop. Their theory was that due to the engine rebuild, which may have included skimming of both the head and block, the studs could have been rendered too long in relation to the acorn nuts. Hence the acorn would interfere with threads of the stud during torquing, leaving limited force to compress the head gasket resulting in the inevitable leakage.

After remedying the nut/stud situation and extensive test driving by the workshop it appears as the problem has been solved. More test driving is to be done, but the outlook is very positive now. Unfortunately I don't have any opportunity to collect the car this year, so it will only be put to full test next year, when I hopefully will be driving it much more frequently.
New expansion tank.


New hoses.


External coolant leak.


The old expansion tank.

 

Quite an adventure , glad you escaped another head gasket replacement. The S1 overflow tank set up is interesting, seems much more practical/accessible than the S3 I am familiar with where its buried up in the wheel well.

 

Very well thought through diagnostics, well done.

Stretched head studs willl reek havoc.

Sounds like it is sorted, those test drives are usual a tad brutal.

 

I had that problem once.

The XK head (at least as used on the Series III XJ6s) has ample 'meat' to skim off. In my case the head had been skimmed a full 100-thou. That's huge. Additionally, I was using aftermarket chrome head nuts which were (I found out) a bit less deep than the originals

Long story short, the nuts were bottoming out and I wasn't able to properly torque the head.

The fix was using double washers under the head nuts

Cheers
DD

 

I am based in Sweden, where the car also has been located since new. Let me share a few pictures f it.

 

A very beautiful example, seems your patience has paid off!

 

Very beautiful indeed, every bit of it.

 

A really lovely car !!


Domed head nuts bottoming on the stud is a well-known syndrome and in the Series 3 Workshop Manual I had, it was mentioned. It especially needs checking out when studs have been replaced. Some are a little longer than the others to cater for the lifting brackets. Also the stud holes at the bottom of the water jacket can get filled with crud if the studs are removed for replacement and the threaded holes not cleared out. The new ones then don't go all the way down, thus causing the nuts to bottom.

 

Cant be many S1s on the planet that look that good, especially ones that are driven. It must have been well looked after through your winters to arrive in 2016 looking like that. Well done on your purchase :-)

 

MAAAAATE, that is one TIDY Jag.

They are just so special when kept as made.

It is a real credit to YOU and the previous owners/caretakers.

 

Sweet, love it.

 

The credit for this cars fantastic condition goes to the previous owner, and the appointed workshop. In the course of the previous owners 18-19 years of ownership a lot of things where restored. New interior, new chrome, new wood, stainless steel exhaust, rebuilt engine, restored IRS etc. The owner before that had taken care of any structural repairs and a full respray (which still looks great). The only major component that hasn't been restored (as far is known) is the auto gearbox, which works flawlessly anyway.

My task and intention with this car is to stay atop of any issues while making small improvements here and there. And, of course, to enjoy it on the roads during the summers.

I don't know much about the early history of this car, but I intend to do a bit of research into it. What I do know is that it came into enthusiast ownership already in the early 90's, after which it has been very well looked after.

 

I add my Ditto, very tidy, indeed.


A car to steward and enjoy.


Carl

 

I am a huge fan of S1 cars and this one is frankly magnificent.

The gear stick handle looks unusual?

Any chance you could post a picture of just under the dashboard/above the shelves? Mine has really cheap felt and is all torn up from various work on the car. Just wondering how restorers thought to make it nice again.

Wonderful car: thanks for sharing.

 

Beautiful car!!