Folks, to divert the subject slightly, I've read in a lot of posts about XJS's that the shroud flaps get hard and brittle, as mine are. They would be easy to replace but has anyone a recommendation for what material to use? Would 1/16 silicone rubber be OK? Thanks

 

I think that probably, if all is Ok at 70°F, and the engine starts getting really hot at 110°F, it is an airflow/heat transfer problem principally. FWIW, I think that 110°F as a shade temperature, eg 125° in full sun, will tax ANY system on an XJS V12. But, While I think the engine temps at 210°F will not result in any damage, clearly the margin of safety is very thin indeed! If the temps come down as soon as you spped up a bit, that would confirm a top quality electric fan setup would improve things.

Undoubtedly a top quality electric fan setup will improve slow speed/traffic halt cooling, as this is the time the mechanical fan is at its slowest speed. There is (I have read) a very effective twin electric fan drop-in system available from a US supplier (possibly V12S, I have forgotten) that comes complete with new shroud, extra transmission cooler, all wiring etc etc, all ready to put in with no fettling needed other than removing the original fans. Quite expensive at (I think) about 700 USD. But it does the job, apparently. In your climate, if I had the cash, that is what I would do!

My radical "bumper slot" is just about impossible on a facelift car, so I think it is a question of living with it or spending the cash on an electric fan system - either one you make or a ready-to-go one. Grant Francis in Australia has a twin fan setup from an Ozzy car that works a treat and is cheaper than the option above, maybe such a system can be bought in the US and fixed in relatively easily?!

Greg

 

Your symptoms are very similar to mine. You are basically running out of margin. The hottest mine got was right at the end of the "N". I was getting around 235 IR readings on the to hoses. It took around 10 minutes for the aux fan to stop running after I shut down in that condition. Now that I am "fixed" I never get further than half way into the "N", I'm reading 195 IR on the top hoses and my aux fan shuts off after less than 60 seconds. You're going to have to start thinking about a cooling system refresh.....

 

Thanks for the advice guys. I'm sure a good fan set-up would solve the low speed/idle concern. After I purchased the car, the first thing I did was address obvious cooling concerns: radiator, stats, flow, fan clutch, fan switch, etc. Other than a new water pump, I'm not sure what else could be refreshed. I suppose that could be a concern, however, the coolant flows well. The stats were not physically measured however. Therefore, I am somewhat concerned they may not be sealing the bypass completely.

Thanks again, I did not mean to interrupt this thread. So I can readdress in new one.

 

Check for debris between the condenser and the radiator. There is about 3/4 inch between them and leaves/junk will build up between the 2.

 

Yes, that was cleaned when the radiator was removed to be rebuilt. There was some debris there.

 

Mine is doing the same... over N in stop and go at stop lights... normal cruising....
read on jag lover that our over flow (expansion tank) is in the fender behind the front drivers side (US LHD) wheel...
traced the pipe back and yes in goes through a hole in the bodywork into the fender...

so I checked my water level... it is low.... added half a gallon distilled water and have to leave the car and com back to work (it was lunch time) will see if it takes more later... and if that cures the warm at lights....

if so I will have to inspect the expansion tank...

 

That is quite a bit of water, but if it keeps doing it check out your fan. Even if it runs the stock fan is pretty crappy and even a 20 dollar ebay fan can do a better job.

Get a IR thermometer and check the actual temps to see what "above the N" really means

 

had the better half pick up 2 more gallons of distilled water
went home after work... checked to see how much more water it would take to filler her up... took 90% of the next gallon... so about 1.4 gallons down on a 5.4 gallon system.
check 12 hours later and level was normal no leak... (non running hours)

I drove her to work this morning (it is cool out though)
the temperature did not even get to half way in the normal
it is a short drive... though but before it would get to half way really quick and then in stop and go it would heat right up to 3/4 on the gauge and make me very concerned...

so at lunch I went out and checked the coolant level put .4 gallons in this time green coolant was visible when the other tank showed I had filled it... last time it showed clear fluid (water) it is mixing...

drove across the parking lot parked not under a tree and dropped the hood (conv top) put it back up... GEZZZZ! the passenger side rear quarter window worked... put the top up and down about 4 or 5 times.... every time the passenger side rear quarter window worked... but not the drivers side... ahhh.... I WILL WIN...

 

Check that the tube from the wing tank to the overflow tank is not blocked. If it is, you are effectively pressurising the system above the rad cap limit. Also check that the overflow tank in the space behind the LHS front wheel baffle is not leaking or broken.

If that is Ok, I suggest you park on an uphill slope, or raise the front end, then switch the aircon to FULL DEFROST (right hand knob at 12 o clock) warm up the engine a little, and engine running remove the wing tank cap and fill the tank. Then replace the cap and remove the centre cap and fill there and replace. Then remove the rad top bung on the US driver's side of the rad and see if coolant runs out. If so, all well, if not put more in the centre fill until it does.

Also, while cold, check that the tube from the centre fill spout to the rad top on the US passenger side is not blocked, and ensure the banjo bolt it goes to is cleaned out.

If all this is done and Ok you should not need more than a pint or two from then on.
Greg

 

Bocagp45,

I recently purchased an 96 XJS 4.0L convertible 2+2

1. When you filled the system did you make sure the heater was on and calling for heat. This should ensure the entire system is full. You may still have air trapped.

2. I too live in Fla. Venice. With the 90degree days from a few weeks ago I had the same issue. In stop and go traffic it would overheat w/air con on ~3/4 gauge and the fan would not go on!! Highway driving no issue!!

3. I installed an auxillary fan because the factory aux. fan shaft was frozen/would not turn. The guys I think JapThug sent me a diagram that allowed me to be able to run the aux fan both manually and bypass system controls. After installing the fan 10" ~750CFM in traffic w/fla heat ....No Issues!!

4. An old trick I did with my Merc 560SL was to drill 5 ..1/4" holes in my thermostat. It also worked for that car!! Kept the water flowing all of the time. In colder up north weather this would not be recommended.

5. Don't know a lot about the XJS (Not sure what engine you have) mine is 4.0L. Is it possible to install the thermostats incorrectly (highway speed not an issue).

The group on this site is really great and they will help you get this resolved.

GOOD LUCK!!

 

Drove her to C-fil-A
waited in the drive thur...
temp just below the middle the whole time
with top down and ac on... then off then on... no change...
on returning to work and shutdown... electric fan running when I walked away...

<GRIN>

 

That tank in behind the fender you can ditch. My car has not had this since I put her back on the road, No overheating even in stop start traffic in 40°C heat.

 

late reply but for what its worth... I had all the same overheating issues, we restored the car from an engine fire barn find, so had all new hoses/rad/t'stats/etc replaced. The car ran well, really stable N even on 40c day in heavy traffic, could not understand what all the fuss was with the overheating... then we noticed the needle going high in slow traffic/mild weather. checked it all pored over these threads etc. then read the above comments on the overflow bottle. this being hidden away was not even considered as an issue. but having ruled everything else out, decided to check it out. I found the bottle half full of dirty water/mud, so this was cleaned out and refilled. while putting it back together noticed the hose connecting the header tank to the overflow..
What can go wrong with a hose you might ask?
For the sake of thoroughness I disconnected it from the header tank and tried to blow through it - no dice. on further inspection there is a short piece of steel pipe in line where the hose goes through the inner fender which was completely blocked right through. In fact I had to drill it out to clear it!
Where did the coolant go when the car got hot? I borrowed a pressure tester from a mate and pressurised the system while cold, then crawled under and nipped up 6-7 hose clamps 1/2 turn to stop the leaks, Presto no more coolant loss no more overheating, rock solid N on the gauge. Note none of these leaks were obvious in use.
Lessons learnt - For the system to work everything needs to be working and in good order, then it will work well, be thorough and methodical, don't ditch the overflow bottle, the system needs to recover coolant as it cools. Follow the instructions in the manual when topping up the coolant, Don't put Bars leaks in the system!!! (as per the manual)

 

It should be called BARS-STOP FLOW AND CLOG THE SYSTEM TREATMENT

 

I think that tank in the wing is nothing more than a rust trap and I would not be surprised at the number of owners who are not even aware of it's existence. Ditched it some time ago.
I am not sure when the "environmental catchment tank" first appeared but I ran a '73 xj12 for many years without a hint of trouble and it had no more than the header tank in the engine bay. The engine cooling system recovers all the coolant it needs as it cools from that tank unless there is a leak, in which case no amount of extra tanks will help suck back into the system.
After total fill the overflow from the system at operating temp. is only about 1/2 litre which is more than covered by the one tank.
Totally agree regarding Barrs leaks though.

 

I agree, I do not run an atmospheric recovery tank either.
Greg

 

This is my tank.

1ltr Moreys bottle (must scrape that off one day, maybe).

Beem that way for 10+ years.