I think I screwed up. I ordered a gorgeous aluminum radiator from V12 performance. Fairly easy install, beautiful quality, all was good. Until I went to put in the banjo bolt on the passenger side. It leaked a little at first, so I removed it and went to put it back in again, but I think I stripped some of the threads because its not catching anymore. I know that the banjo connects to the air bleed system, but is that air bleed totally necessary? I.E. what would happen if i plugged the hole? That is probably a dumb question, but I'm terrified that I'm going to have to do the whole job again. Any ideas??

 

IMO - the banjo bleed is totally unnecessary and I will be deleting it when I install my new engine. The radiator top is not the highest part in the system and the banjo only bleeds air from ONE bank the Left the banjo would need to be in the RH end tank top to bleed both banks. Take a look at what Ford did with the cooling on the XJ40 V12, much simpler than the XJS and I have never heard of an XJ40 V12 overheating.

 

how much meat do you have to work with? Can you just stick a helicoil in it? Maye cut it and have a local welding shop add a new bung for you?

On a side note, is there any particular reason you got a radiator from v12 performance and not one of the common $200 3 rows that is now available? I can't really tell what the "Catcooler" offers over other rads that are significantly cheaper.

 

Coventry fan:
I think the bleed tube is important, and I would not eliminate it unless you reorganise the entire coolant circuit- which is doable as I have done it. As the rad is slightly lower than the highest coolant point of the engine, and as the header tank is FAR lower, without the bleed circuit I think trapped air can accumulate in the radiator to the detriment of the cooling.
greg

 

Warrjon
The banjo is in the RHS of the rad (ie A bank side). On the XJ40 V12, the coolant circuit had a header tank higher than the rad and higher than the engine. If you can arrange this in an XJS (as I have if you recall; but it is a far harder task with ABS equipped cars) then the bleed pipe and banjo AND the spout on the crosspipe can all be done away with.
Greg

 

Well, luckily I was able to get a corresponding metric nut, and clean up the threads on my original banjo bolt. I also grabbed a regular bolt and ran it in and out of the hole in the radiator to make sure that all the threads were as sharp as possible. After doing that, I was able to get the banjo bolt to bite and tighten down *sigh of relief.*

So now, need to bleed the system. In following all the instructions I've read, I opened the caps on the filler neck and the expansion tank. Then filled the neck and started the engine. To my surprise though, coolant started blowing out of the filler neck. Any ideas on that?

Pertaining to the radiator I picked, I liked the fact that it was totally direct fit. Everything that I've read seems to suggest that a lot of the 3 row ones end up needing modification. This one needed nothing, and is from Wizard Cooling who I have always heard good things about. Certainly more expensive, but YOLO...

 

I'm still convinced that the system has some kind of 'self bleed' setup already... But that is just me

 

The water pump is pushing the coolant out!
I suggest you bleed as follows:

1. park the car on a slope nose up, or jack up nose a bit
2. remove both caps and top up at centre cap until water starts coming out of the wing tank
3. replace wing cap and keep topping up the centre and replace centre cap when upright tube full
4. turn heater control to DEFROST
5. start the car and let it tick over for a couple of minutes
6. on the LHS (US driver's side) of the rad is a brass plug (at least on all OEM rads) roughly in the opposite position from the banjo bolt.
7. remove this plug and let air bubble out, squeezing the top hoses is a good idea to aid this process. If air is in the rad and no more bubbles, pour coolant into the bleed hole
8. turn off engine and top up into this bleed hole if necessary and replace the plug
9. remove centre cap and top up to the top of the upright tube.
10. remove wing cap and top up if needed
11. check centre cap level and wing tank level after doing a decent 20 mile drive after the car has cooled.

Note that there is an atmospheric catch tank behind the LHS front wheel in the wing cavity behind the wheelarch baffle. The overflow tube from the wing tank goes to this tank. It is very important to ensure this tube is free and not blocked. Remove the overflow tube from the top of the winf tank and blow though it to ensures it is not blocked. If it is blocked, until it can be fixed, run an overflow pipe down to the bottom of the car.
Greg

 

yeah it seems pulling the other cap off and filling to overflow does a pretty good job. My top hat seals leak and ive refilled coolant in various areas before and simply put the cap back on and driven with no issues from overheating due to air.

 

Thanks to Greg for the excellent instructions for bleeding the system. It took a few trys, but I seem to be in good shape. I finally got it to run on the interstate with the needle actually BELOW N, and it was in the mid 90's here in Virginia today. Can a little air in the system really make THAT much of a difference? It ran over N until I came home, let it cool, and topped up the system. I felt like I didn't really have to add that much, but it certainly seemed to make a huge difference in the temp!

So, assuming she continues to run cool, this weekend it's pads, rotors, calipers, and wheel bearings for the front. Also a good time to install these Kleen Wheels that I ordered the other other week. Hopefully this will help with the incredible amount of brake dust this thing produces. Thanks to everyone for their support!

 

l pretty much agree Daim.
I have been running xj12 or xjs since the 70's and have to this date never had to stand on my head nor perform a cartwheel in order to bleed cooling system and never had a cooling system problem.

 

I am glad it is sorted, great job.
When you do the new bearings etc, look very carefully at the stub axles. If you see circular marks where the bearing inner races were, and can run a finger nail across them and can feel a ridge, I really think you should replace them. If not, you will gradually hear knocks after the rebuild, and believe it or not, this will be the cause.
Greg

 

 

I have just tried to bleed my cooling system after having refurbished and adjusted AAV.
I have done it before, where I got a fair water flow out out the bleed screw on the radiator, but this time I failed to get any water out.
Compared to the above instructions I had both caps on, when I tried to bleed it. I had quite a lot of overflow from the central filler, and I did therefore put the cap on.
Will this prevent bleeding ? I was parked on a slope and I even tried to lift front left corner further to no avail...
The hose from the radiator in top left feels as if there's no water in it. That cannot be good...
My bleed screw cannot be removed, so filling the radiator from that point is not possible. It turns maybe 5 turns. LH thread by the way, and closed when screwed out, pretty weird.

 

going by my understanding of the cooling system of these cars, the highest point is the bypass pipe with the filler cap. The hose from the banjo screw/bleed pipe leads to the highest point. In the highest point is a one way valve, only allowing flow from the radiator to the cap... A typical sign of a bleed valve. The bleed pipe is higher than the radiator bleed valve. The B bank thermostat housing has a hose leading to the bleed pipe on the radiator. Again allowing air to flow to the highest point...

The bleed screw on the radiator is probably just a 'quick bleed' to make the radiator efficiently be bled... I really mist look into my repair and service manual... The X308 has a self bleeding system, which isn't really that far off of the XJ-S V12 setup...

 

My procedure for 1989 car is both caps off, radiator bleed screw out fill through crossover until coolant level is at each of the three points which are capped in turn.
Start and run car for two three minutes, turn off and then recheck at same three places adding coolant to fill once again, replace all caps and done.
I do not have the spigot valve on the crossover pipe nor do l have an atmospheric tank.

 

I was just preparing to change coolant in my six cylinder 1993 XJS. Planned to remove the lower radiator hose from the radiator and dump the coolant. Will open heater prior to dump. Will reverse procedure to refill. Is there any special action that has to be taken on the refill?

 

Thanks. I will give it another go, this time with horizontal car and open caps.