Good for you!

They are wrong, and you are fortunate to have recognized the issue before it was a more painful lesson.

The single most important tip I can give you before start working on the V12 is to have a camera or cell phone handy, and take pictures of anything you're going to touch *before* you touch it and during as you reveal hidden areas. Trust me, you'll be glad you did.

 

I too have an '88 V12 coupe, and I found my instruments reading the same as yours. However, this was on the test drive after I had replaced the thermostats with 180F ones with jiggle pins, had the radiator cleaned and converted to a full dual pass, upgraded to twin electric fans, replaced all the hoses, replaced the coolant temp sender, and bled the system properly. Fortunately, I had my hand held IR thermometer with me. So, I pulled over to take readings off the thermostat housings and nearby hoses and everything was within spec for 180F thermostats.

My fuel gauge also read 3/4 after I filled the tank. I ended up having to pull the cluster and clean the contacts as outlined in Kirby's book. However, as Greg in France says, this is very delicate and detailed work. After all, the temp gauge is really only a suggestion as you have found in Kirby's book since it can't give you actual numbers throughout the engine.

I'm not suggesting that you skip replacing aged cooling system components as others have recommended, but don't be discouraged if your gauges still read the same after you complete these tasks. As Doug suggests, I highly recommend an IR thermometer having been in your shoes.

BTW, after cleaning the contacts on the instrument cluster and adding another ground, the temp reads at the bottom of the N during normal operation and the fuel gauge gets almost to the top on a full fill. I suspect the contacts on the fuel sender are at their end of life. If I read Kirby's book correctly, I believe our '88 coupes have the upgraded fuel float. I guess I'll know when I eventually get to it.

 

I have a 1988 Jag Convertible and back in July, I had the same problem with the temp gauge needle always sitting half way between the N and the H.
And the car FELT like it was running way too hot.
So I got the following work done

1. Remove and recore and refit the radiator
2. Fan clutch was faulty so I had the fan system replaced with a twin thermo fan conversion
3.Replaced thermostats
4. Outside clean of oil cooler to remove build up of incoming debris
5. Replaced top radiator seal
6. Not sure what to extent cooling system was otherwise checked or cleaned or "bled"

Since then, for all the driving I have done (mainly city stop and start - and its been pretty constant), the needle on the temp gauge sits right at the very TOP of the N (but not above the N

Yesterday, I took the car for a run to the country and after clearing the stop start traffic in the city (with no issue with Temp gauge) and getting up to 100k speeds on the highway, the temp gauge needle started to climb and started heading BEYOND the middle of the top of the N and the bottom of the H. And I noticed this happened when going UP HILL.

I pulled over, opened the bonnet, left the fans running and checked the oil level and looked for any leaks - all OK.

Let the car cool - drove the 100km home and the needle sat just between the top of the N and slightly above - but never completely cleared the top of the N.

There was no up-hill on the way home - and the car did not heat up in stop start traffic

I am really bewildered that after all the work done, why the car got over-heated yesterday (What I did not do was check the radiator coolant level - for obvious reasons - but I am going to check that this morning) and why it did not overheat on the way home

******************** UPDATE ************** Checked coolant level this morning and I was only able to top it up with 1 litre. (I opened both cooling system caps - when I opened the second one in the middle of the engine bay, it hissed and gurgled as though pressure was being released)
I then checked the thermostats and they are both working OK. (Started the car and monitored the temp of the radiator hoses till I was able to confirm that hot water was flowing through both of them.

The only difference was the uphill climb on the way out when the car actually overheated

PS. My engine oil seem really really thin - I put some on my finger and rubbed it and it didn't seem that oily - I know there cars are meant to have quite THICK oil (correct?) Oil is totally see through with a slight oil colour tinge - so oil looks good in that way.

All comments, input and observations really welcomed

 

That is really disheartening that you did all of that and still are overheating when pulling a hill. There must be something else wrong. Did you put those Tefba filters in when you were doing the work? If not is it possible the radiator is clogged again?

 

Hi Workworkwork
Thanks for your empathy - much appreciated - No until now, I had not understood that there was such a thing
I am taking it back to teh garage tomorrow that did all the work and will ask about those filters - They sound good -
But I wonder why it only overheated going uphill?

 

Proper bleeding is important. If the repair shop doesn't know the correct V12 procedure ...ask them...you may have some air pockets.

Cheers
DD

 

Redgear,

Sorry you are experiencing this, but here are a few of thoughts:

One would be that the system wasn't bled correctly and there are air pockets in the system.

Two is that in replacing the radiator they didn't renew or replace the foam that insures that air flow goes through radiator rather than around it.

Additionally, the type of thermostats used in the replacement could be an issue.

Your banjo bolt or air bleed tubes could be clogged.

If you aren't at the bottom of the N going down the highway after all that work, there is a problem.


Edit - I see Doug beat me to the bleeding issue. If you haven't done so, reading the entire cooling section of the Palm book is very helpful in understanding what it takes to sort out the system.

 

I can tell you one thing that was well and truly properly bled....

Was my bank account

 

I was actually in the workshop when they were re-fitting the radiator and I asked why they were using the old foam as it was filthy and looked as though it was disintegrating - so I asked them to put in new foam - maybe the new foam lets too much air through if it is not "the right" foam - but these guys only work on Jags and they seem very knowledgeable...

What is the characteristic of the thermostat are we talking about -- the temperature at which it opens, or the manufacturer/quality of the thermostat - or something else?

What is this banjo bolt - and what is th effect of the bleed tubes being blocked - does the system self-bleed during operation?

You are absolutely right on that point - Its been very disappointing

OK - Good advice - WIll do!!

 

If this were the case, why would the problem only show up now, which was when the car was doing a fair bit of ascending ( going up a hill

...Although, as you said, if the needle is not at the bottom of the N, after all that work, then there is something not right.. but I have been driving in really bad stop-start city traffic and it has never budged above the top of the N."

 

Most every thing else is well covered. I might have missed something and therefore one or more of these comments are redundant.


1. The engine is working harder going up hill to overcome gravity. Even slow stop and start isn't likely to be creating as many BTU's as the former. However, a cooling system in proper shape should be able to handle that. Something is possibly amiss.


2. Use the IR to read real temp's in real time.


3. The guage on my lumped XJ wuzza 6 rides at about 100C. The LT1 was designed for that.


4. Air flow. Not only leaks at the side of the radiator, but the air dam under it.


5. A really hot engine makes no bones about it, it gurgles furiously!!!


6. If ion a spot, pop the bonnet to the safe latch. Best at less than high speeds.
The added airflow can make a big difference. Exhausting hot air from the engine bay isn't the best feature of the cooling system in these cars....


Carl

 

Jeff Isbell wrote a book on the cars, A lab like dissection fore and aft.


Carl

 

Remember, though, dear ol' Kirby has a very limited definition of "overheating". That is, if the coolant temp is running higher than thermostat control range, you're overheating.

If you have an 88ºC thermo the temp should ideally 'hover' at 88º as the thermostat continuously cycles. If the coolant got hot enough where the thermostat was constantly fully open....say 95º or so....Kirby would call that 'overheating' because it is out of thermostat control range.

At the other end we have overheating defined as 'boiling over'....about 130ºC at 16psi

Although the temp gauges can vary from car to car, 'top of the N' would probably be about 92-94ºC or so (about 200ºF) in most cases.

"Above the N" might mean as little as 95-100ºC ....which hardly raises an eyebrow in most circles. We've been indoctrinated to panic.

The important thing is that the temp doesn't keep climbing up-up-up with no end in sight.

And the really important thing on a V12 is full *flow* throughout the engine. 100ºC won't hurt anything if the flow is 100%. OTOH, 80ºC could be a disaster if the system doesn't have 100% flow.

In a perfect world every V12 would never stray from the middle of the N and *never* climb out of thermostat control range. The world is imperfect, though

Cheers
DD

 

Not sure, but air in the system can cause strange behavior. In any case, if unsure, it must be eliminated as a possibility.


Or not.

Have you used a hand held infra-red thermometer to get an idea what 'bottom of the N' and 'top of the N' really is....in actual degrees? On your car (but maybe not the next fellow's) it might be 80ºC and 90ºC respectively. In which case 'top of the N' is perfectly OK




Sounds good to me, off hand...but what was the ambient temp?

Cheers
DD

 

Xj "Whatta" 6? - what is a wuzza?
What is an LT1?

What should the V12 see as its ambient (ideal) operating range (obviously 82 C would be the lower limit as the thermos are rated to that



Sorry if this is a really obvious thing ...but, when you say "air dam", exactly what do you mean?



Carl, if you are referring here to when I said my engine was gurgling, that was the next morning when the car was stone cold and I removed the radiator caps to check the coolant levels. When I removed the main rad cap, there was a pressure release and gurgling coming from the cooling system opening

Carl that is a really, really good idea - so what you are saying is - if it overheats, pop the bonnet to the safe latch and keep driving - but not above ??kms/hr??

 

WorkWorkWork

Sorry I just missed this. I have my car stored in Overlea. Have just left there two days ago to come back to Uganda.

I have a similar problem. Unfortunately, I tried ordering the Tefbas, banjo bolt and hoses from V12 Performance. Doubt seriously if I'll ever see them. Check some of the other threads on Brian.

I'm planning on pulling and cleaning/rodding/recoding the stock radiator and following the steps in Kirby's book next May when I return stateside. I've got a private workshop in Overlea.

I also work with a very good private mechanic that will come to your place. I've been working with him for a while and can highly recommend him. He and I just spent several weeks doing all the major systems on my Porsche 928. PM me and I'll give you his contacts. For $900 he would have finished all this work and more.

Pete

 

FasterJags & V12's are no longer in business. If anyone orders anything from there web sites your wasting your time & money. FasterJags (Brian in Dallas, TX) has been gone for a few years, V12's went early this year, I think. V12's were way overpriced anyway. GTJ in Perry Ohio sold great stuff but priced themselves right out of the Jaguar performance parts market.
Lawrence

 

Redgear:


Yeah, I bought a very nice 83 Xj6 in 2001. I used it for a few business trips just fine.
Quirky AC, but all else neat. Then, on a hot day in CA's hot central valley, disaster!!!!
Went home on a flat bed. Diagnosis found 0 compression in all six!!!


Transplanted the engine and transmission from a 94 Cadillac Fleetwood Brougham.
Aka LT1 used in other GM cars and trucks.


Under the car's chin is an air dam. An important part od the airflow needed to transfer engine heat to the atmosphere. Many get smashed and gone. Parking bumps and curbs!!!


The same noises one hears in a tea kettle when the water reaches boil are heard in a car, only much louder.


Popping the hood/bonnet on a front hinged unit helps a lot to lower engine bay temps and allow one to get home.


Done in one way or another since the onset of the IC engine.


Note: After a drive and one shuts the engine down, the temps go up!!
No air or water movement!!!! No transfer to the atmosphere.


Cooling is all about heat transfer.


Carl

 

Lawrence,

Have to dispute your statement. My order was placed in July. Paid through the v12 performance Paypal account. Brian communicated via email. Cancelled payment on that account. Sent me another request from filmproductions. I sent him email, he replied immediately, saying it was a real request.

I paid via that account.

I would say is is inaccurate to say he has been out of business. When I went to write a report on ripoffreports, someone was scammed as recently as Sept.

He is still out there...

 

I bought a aluminum rad, electric fans, filters from FasterJags (Brian) about 6 years ago. I must say the sale went perfect, no problems, good prices. In the past few years though I read some horror stories about FasterJags , read some of the threads in forum archives. Maybe things changed.
Lawrence