Hot Spot on my v12 rad

V12-Engine
1

Started my 87 v12 for the first time this year after an extended winter/spring/half of summer nap and there was a real hot spot on the driver side at the top front of the rad. Hot enough to smoke.

Shut down the car and let it cool off. Fluids are topped up.

Any ideas?

2

Maybe your rad is blocked and the only place where water circulates is the hot spot area ?
How was your engine temp reading ?

Aristides

3

I had a small amount of steam coming from the top right of the radiator, just under the shroud next to the banjo bolt. It would happen off and on???
Eventually I pulled the air bleed tube and banjo bolt off the top of the radiator and all were blocked. Can’t explain why but I haven’t seen the steam since and she runs with the needle behind the middle of the “N” and not the top of the “N”. I suppose I finally eliminated some remnant air pockets.
Trev

4

Thanks for the input.

Will monitor temperature situation. Past problems with car have resolved with regular use. Fingers crossed.

Wasn’t sure if this a common problem. Will let you know.

Viking1

5

Viking1,

You mention “driver side” but that could be either the left side or right side since the XJ-S was produced in LHD and RHD versions.  A better description would be left or right side to avoid confusion. 



Assuming that you are driving a RHD vehicle, I wonder if what you were seeing was a bit of steam and not smoke.   There are supposed to be a very thin crush copper washers (Jaguar part number C4146) on all three of the mating surfaces of that right side banjo bleed pipe and spacer to seal the coolant system.  It is possible that one or more of those washers are damaged or missing and leaking hot coolant when the system is hot and under pressure.   These are very thin copper washers, not ordinary ones you might find at a hardware or auto parts store.   I just measured a used one and it was 0.013 inches, very thin.   I usually buy a dozen or so of them at the same time through the local Jaguar dealership since Jaguar used them on a variety of coolant or oil fittings on my Jaguars.  Don’t use an ordinary washer because they are too thick and will block the hole in the banjo fitting inhibiting coolant flow. 



If you are driving a LHD XJ-S the steam could also be coming from the small bleeder Plug (CAC4723) that is supposed to have a small fiber washer (C930) beneath it.  If the washer is missing or torn, steam could certainly leak past the plug and escape.

Regards,

Paul M. Novak

1990 Series III V12 Vanden Plas

1990 XJ-S Classic Collection convertible

1987 XJ6 Vanden Plas

1984 XJ6 Vanden Plas

1969 E-Type FHC

1957 MK VIII Saloon

Ramona, CA USA

6

Thanks everyone for the input. The smoking has stopped (was on left drivers side) but I noticed that the smaller fan on the left side never runs. Car temperature gets to 80 Celsius and stays there.

Any trouble shooting tips for smaller fan on left? Is there a way to bypass the switch and see if the fan will run? Is there a common problem with these Fans?

I am not overly mechanical but can accomplish some things. Any input on getting this fan working appreciated.

Viking

7

Any trouble shooting tips for smaller fan on left? Is there a way to
bypass the switch and see if the fan will run?

If this is the OEM setup, the switch is on the inlet elbow on the water pump.
Just short those two terminals together with the ignition on and the small fan
should run. It has a bootstrap circuit that will keep it running if you turn the
ignition off, but once the switch breaks the circuit (or you remove the jumper)
it’ll stop and stay stopped until the ignition is turned back on.

Is there a common
problem with these Fans?

First, it might help if you tell us if your small fan has 4 blades or 6. Most
have 4, but I understand that some later cars came with a
higher-performance 6-blade fan.

My 4-blade fan failed. The commutator inside the motor came apart. It was
an odd pancake-style commutator, the brushes move parallel to the shaft
rather than radially. Whatever, I replaced that fan with a junkyard fan from a
Subaru, and later on THAT fan failed, so I replaced it with a fan from a
Mercedes. The Mercedes fan was intended to cool an entire engine by itself;
it was extremely heavy-duty and probably drew a ton of current. Worked
great, though.

I am not overly mechanical but can accomplish some things. Any input
on getting this fan working appreciated.

If it’s not running at all because your engine is staying cool, kudos!

– Kirbert

8

Fan has four blades.

Think I will monitor to see if it runs when the car goes for a good run and heats up a bit. Maybe the fan just hasn’t been needed yet. Smoking problem seems to be resolved. Maybe just dust and bugs in rad.

Thanks for the advice.

Viking1