Today: 'Greg' and 'Grant' got my 1990 XJS V12 Finally Running after being laid up for 16 years, so First of all Well Done Guys and Thank You Very Much, I'm Very Grateful.

All I knew was the Car wouldn't Start and didn't have a clue what could be wrong, which was complicated by the fact that the Car had an Immobiliser, which would not respond to a signal from the Key Fob and so I suspected that was what it was.

But Greg and Grant nailed it straight away as being Blocked Injectors and so off with the Fuel Rail and then while I'm about it, put in a New Set of Spark Plugs.

Which is a nice little job as I'm sure you all know, especially No1 and No2 plugs on A and B Bank, which I don't think had ever been changed.

Replacing the Spark Plugs took me Two Days because I had never done it before and can only compare it to 'Building A Ship In A Bottle' as everything is crammed in tight with little or no room to work.

And lining up the Air Con Motor to get the bolts back in, turned into a 'Nightmare' as its such a tight fit in its mountings, that it was one hell of a job (at least it was for me)

Cleaning the Injectors took about a Week, because I wasn't prepared to pay £24 for 12 small rubber 'O' rings, which I eventually found on sale for £4-43p and seemed to be just as good as the expensive ones but time will tell.

Putting it all back together was also lots of fun and gave me a real feeling of achievement.

So all I had to do was turn the Key and She would Start, except She wouldn't!

The Injectors wouldn't Fire and the Spark Plugs wouldn't Spark.

At that point I was totally lost and right out of ideas, not that I had any in the first place!

Greg came to the rescue and knew just what to do and told me to clean the plugs on the Silver 'Thingy' down by the Headlight Nacelle (Resistor Pack to give it its proper name)

As soon as I had done that, I followed Greg's Instructions and Flicked the Throttle Capstan Round while one of the Injectors was inside a glass jar and it started squirting Petrol Straight away!

So all I had to do was turn the Key and She would Start except She wouldn't because the Plugs wouldn't Spark.

Over to Grant in 'OZ' who ran through some tests, where eventually we found that I had put the wrong push in plug in the wrong Transformer.

So all I had to do was turn the Key and She would Start, where to my utter amazement, that is exactly what happened on the first Click of the Key and She ran like a bird.

But then I saw wafts of smoke from the Top of the Engine from residual White Spirit that I'd used to clean out the 'Vee' and She had only been running for about a minute before I switched her off.

So I went and got my Camera as I wanted to take a Photo of her running to show Greg and Grant but fortunately it was raining and you'll see why that was in a moment.

My Plan:

(1) Start her up

(2) Grab Camera Take Photo

(3) Switch her off quick before She started smoking again.

But when I went to Switch her off, the LOW OIL Light was ON! so I switched her off Quick.

She had only been running for about a Minute and I'd even Checked the Oil the previous day.

But somehow the Oil Cooler had developed a major leak, so when I shut her off I pulled the 'dipstick' which showed an Inch of Oil the first time but when I re-dipped it NOTHING! All the Oil had gone!

So I was very lucky that I shut her off when I did and even much more fortunate that it didn't happen on the Road (not that She is ready for the road just yet)

I've had Oil Coolers go before and trying to get the Pipes off, is the Job from Hell and in fact its almost impossible as the Corrosion tends to Weld them together, not to mention also Very Expensive and makes changing a Radiator a Walk in the Park.

But the Previous Owner of my 'Scrap XJS' had the very same problem and as such had a Tube made up to By Pass the Oil Cooler altogether and as I have still got that Tube, I was thinking of doing the same.

As compared to replacing the Oil Cooler including all the Oil Pipes that you need to have made up (unless you want to use OEM) which will cost you a Fortune.

Fitting this Oil Cooler By Pass Pipe is a very cheap and easy fix.

So my Question is what are your Thoughts on running an XJS V12 Without any Oil Cooler?

The Picture is of the By Pass pipe that I am talking about.

 

In a word ....No.
These cars need all the help they can get as either originally designed or after market enhancements to run within designed operating temperature ranges. Keeping the oil temp in check helps the internal lubrication and cooling system prevent metal/aluminum overheating - the #1 killer of the V12 engine.

 

+1 on the "No" advice.

I have an oil temp gauge in my XJS (sender is braised into the sump)

Oil temp regularly gets up to 200deg F, so who knows what would happen without the cooler.

 

that seems like a smart idea to have an oil temp gauge.
Maybe someone is brave enough or has experience proving that the oil cooler is not needed but I personally would not venture down that road. I'll keep doing everything I can to limit or control the engine heat rather than tempt fate by doing something that will increase the internal engine temps.

 

In principle I agree if the car is being driven as intended. But while you get the thing going properly and are mucking about getting it an MoT etc etc, using it on the road for short journeys if at all, just having it tick over at home, no harm will come.
greg

 

There was a bit of a discussion about this sometime ago, where there was quite a difference of opinion.

So I'm looking at this as a Temporary Fix in order to get the Car Mobile, to check for things like Stuck Callipers which will need replacing if they are and also Circulate the Antifreeze in my New Rad.

 

Hi Greg and (Grant)

Thanks for fixing my Car!

I just want to put the By pass on to shake down any faults that I might find and just get her mobile to drive her round the Garden to make sure that everything is working and above all turn her round on my Car Lifter.

As it is very difficult to do any work on her where She is

Thanks Again You and Grant both really made my day

 

Hi OB,

Really pleased that you got your V12 running, good luck getting it back on the road.

 

200ºF is about where you want to be...the broad rule of thumb (that I'm aware of) is 180ºF to 220ºF. I'm not sure if there's anything about the Jag V12 that mandates something different than that.

I *think* one of the reasons some V12s have the bypass oil cooler is to help keep the oil in that temperature range. IOW, prevent it from getting too cool. Greg has done a ton of oil cooler testing/research. He'll know.




Cheers
DD

 

What would those ranges be? I've never seen anything from Jaguar telling us.


Personally I disagree.

I think the biggest killer of V12 is dropped valve seats and engine fires.

The former is primarily caused by coolant flow problems, not oil or coolant temperature. The latter is primarily caused by fuel and ignition system problems.


Cheers
DD

 

Hi Paul Cheers

I cannot take any Credit myself, I just did what Greg and Grant told me to do from hundreds of miles away.

And King of France and The Wizard of Oz, went and worked the 'Magic' once again.

 

I think it would be interesting to have an oil temp gauge and see how much driving really *is* needed to raise the oil temp to a dangerous level without the cooler.

Cheers
DD

 

Hi Doug

Cheers that would be interesting, I wonder if Greg can come up with something?

Like maybe draining an Oil Sample out from the Dip Stick and measuring the Temperature after a Hard Run.

 

most V12 engines overheat because of overheated oil caused by cooling system problems!

most people after much cooling probs are taken care of , are satisfied,wrong!

but reading TWR race cars they finally(using all new components) still had some heat troubles, they finally went to 2 large oil coolers,(and some oil sump mods), before they could keep the engines cool!

 

Doug, OB,
With the oil cooler (bypass system) working properly, even in 35C ambient temps, oil temps in my car never exceeded 85C even when driven fast road. The temp drop across the cooler was 20C. The oil temps were measured as maximums all over the engine (oil filter, cooler in and out, sump, cam feed).


The easiest way to do it is temperature strips, which just stick to any cleaned surface wherever you like. Based on these measurements, my view is that in normal UK ambient temps, a cooler is probably not needed for sedate driving.


OB, as you have got your cooler bypassed, why not treat yourself to some Racetech oil temp strips Range B (71 to 110 C range) and put one on the filter and one on the sump and let us know what they read as you use the car. My betting is that the oil temps stay well below 90C in UK autumn weather.
Greg

 

Greg, are those temperature strips a use once only item or can you leave them in place and they will continue working?
A slight hijack here but my boat engine overheats (although the gauge is about 54 years old now!) and I was thinking about those strips for that as well as for the V12.

 

You can leave them in place indefinitely, as far as I can tell. They look like a mini thermometer about the size of the side of a matchbox. The scale goes dark as the temps rise and always stays dark, and thus shows only the highest temperature reached. But they go on working and will show a higher temp reached at a later time.


Greg

 

Ah, ok, so they won't actually show if you are running any cooler after running hot, only the highest temperature reached.
So if you think that you have fixed the problem you would have to put a new set on to compare the difference with the first set.

 

That is correct Steve, but for real time temp readings, the best way I have found is to buy a 10 quid digital reader such as this one I bought. Magic, just tape the sensor wire onto the think you want to measure. A really good piece of kit and hardly any dearer than a packet of temp strips.
Digital Thermometer 2 K-Type Temperature Thermocouple Sensor Probe | eBay


Greg

 

Hi Greg

Thanks but could I not get the same result (on the fly) by using my Hand Held LCD

Digital Thermometer Gun?