I am a new member. But anyway owned my 1986 Jaguar XJS V12 for 4 years. It has been in storage for a full year without being started.

I flushed cooling system, radiator flows great, thermostats were tested and work fine, installed in 12 o'clock position. Bled bleeder on top of radiator. All new plugs, wires, fuel, filters etc. When I aim my friend's infrared thermometer at thermostat housings,

I am getting 280-290 degrees on driver's side housing and 270-280 on return radiator hose (so thermostat is opening.?)

On the passenger side I have around 190-200 degrees and return hose is 190.

Why would it be running so hot on the one side? Bad oxygen sensor causing leaning??

Any ideas?

A Jag lover

 

Check to see if there is a miss on that bank. I had the same prob. i replaced all my plug wires and it fixed it right up.
also there could be some stuck air on that side still.

 

I am not 100 certain, but I think I read about XJS running hotter on driver's side. this is due to a triple core design of radiator, which somehow cools one side slightly better then the other. However, 290 degrees is 143C, which would make your engine boil. Are you sure, the difference is so big and does your coolant boil?

 

It has all new plugs and wires. I am shutting it off when it hits these temperatures. I don't want to damage engine, so not sure what would happen if I left it run. Just in my experience it seems so hot, yet the temperature gauge reads slightly below the middle. All fans are coming on and functioning properly.

 

mines hasnt boiled before.
and yes thats right the drivers side does run a tad bit warmer. but yours is running way to hot. id be careful. what does the temp gauge say? is it at the middle of the "N" or is it higher?

 

could be air. these things are such a pain to figure out cooling probs.
are you getting puffs puffs at left the tail pipe?

 

No puffing of white smoke or anything. Just drove tonight for 15 minutes. Temperature gauge goes right up to the middle and no higher. Pulled in gas station and tested again with infrared thermometer. 275-290 degrees on drivers side thermostat housing, and 210 on passenger side thermostat housing.

 

You might have partially blocked radiator, I think one of the cores is bad.
These are triple core, and one side gets more cooled then the other, due to some blockage, perhaps?

 

The puffing shows if there is a miss, i always know when i have one when the rear end is not a perfect steady exhaust note on the pipes. always is on the left bank.

Thats still really hot.

 

Just to be certain you don't have any air in the system, remove the coolant temp sensor and check if there is coolant right there. If you see any air, top up with coolant through the CTS mount hole. This is probably unlikely but may as well eliminate the cheap / easy fix before moving on to the radiator.

By the way, the radiator isn't hard to remove, definitely not as bad as everyone makes it out to be. For my $.02 there's no reason not to pull it and take it to a rad shop to have it cleaned out and flow / pressure tested.

D

 

It is unlikely to be the radiator if the RH bank is running at normal temp. There is only one input to the engine from the radiator so both banks are getting the same water input temperature.

There is a pipe that runs along the side of the engine - this is the water outlet pipe and is connected to the engine in a number of places along its length, check the temperature at the back as well as the front. It has the thermostat housing connected to it at the front.

You can check your radiator by pointing the pyrometer at the output pipe it should be at least 30°C cooler than the input. I am a little suspicious - if you had a major temp issue the radiator output temp should be increasing which will cause the RH bank to also increase in temperature.

 

If you still have a LH overheating problem, bring it up to operating temp then disconnect ALL of the Fuel Injectors on the LH bank - start it up and re-check the temp on the LH bank, don't run it for too long a min or 2 will be ok, as the ECU averages the output of the 2 O2 sensors, it will make the RH bank run rich.

 

Thanks guys for all input! I removed radiator and had it tested and cleaned at a radiator shop. The car is running much cooler now! Thanks!

 

It is not easy to be right every time, but I do it anyways