Concerning: '97 XK8 Coupe Re-Animation Project

Howdy everyone. I'm back!

Have the engine running nicely on the coupe, but it would overheat after a time, maybe 20 minutes or so. No heat inside (though the A/C works fine).

Replaced thermostat. I believe it's a 180 degree unit...Went into Advance Auto and said gimme a thermostat (politely of course)!

There was no thermostat in place when I put the new one in.

Now it takes about 5 minutes to overheat.

Gets up to about 180 on the code reader dash, then skyrockets. I shut it down immediately or once when driving around block, almost immediately.

The lower hose doesn't seem to be terribly hot while the upper hose is quite hot.

No codes.

No splashing coolant.

Fans work.

Water pump looks like a new metal job...but who knows?

Water pump?

One way valves installed backwards?
Don't know if there are actually such valves, but I recall seeing them mentioned in the manual, but not a picture.

Air bubble (s).

Something terrible?

As always, any advice is always appreciated.

 

The missing tstat and possible new pump is an indication that someone was trying to fix the problem. Did you have a functioning heater before installing the tstat? It's possible that the both the heater core and radiator are at least partially blocked, or maybe the heater pump or solenoid are not working.

This is going to take some digging around, so I would start by inspecting the water pump and also make sure the tstat is installed correctly. That's the reference to the one way valve, I think. It's that little thing at the top of the tstat. Then refill and repeatedly squeeze the top hose with the pressure tank cap off to eliminate air.

 

I found some information that might help another owner fix their overheating '97, but after replacing the thermostat and water pump, have found no joy.

It turns out that my '97 Jaguar had a '98 or later coolant reservoir installed. (Of course!) The '98 reservoir has one of the hose fittings blocked off. You can still use it in a '97 but have to swap the position of the hoses so the open fitting and hose goes to the thermostat tower. The blocked off hose goes to the top of the radiator. TSB 303-15 details the issue. After swapping the hoses - and flushing the system with a chemical - my car took in substantially more coolant.

Also, another owner might be interested in knowing that the radiator drain plug is on the passenger side of the car. Find the Lower A-arm bushing (it will hit you in the face) then look or feel forward for the little rubber (screw) plug. Photos and description are also in the "stickies" but this might save someone some time. I spent about an hour hunting for it as it's fairly small.

However, my car still overheats and the heater doesn't work. I'm reaching my boiling point!

 

Chill out , well do the fan test in the morning . The X100 and X308 has a separate electric water pump to bring in hot water for the cabin core / matrix , we'll leave that alone for now and focus on the engine block cooling .

 

Another possibility... The original water pump used a plastic type impeller. Know to come apart. I'd try looking at the thermostat again to see if it has any pieces of plastic from the impeller stuck in it. You said the pump looked new. Could have been a reason the thermostat was removed. FYI, removal of the thermostat tends to do the opposite of what you might think. Could make it run hotter. Water rushes too fast into and out of the radiator not allowing radiator to do its job, to cool. Just a thought. An avenue to try without much cost. By the way, same material could be caught in the heater valve, pump, core. Goof luck, Rich.

 

Having just gone through an overheating experience myself I feel your pain,
Is the fluid in the expansion tank getting hot?, you can run with the cap off, it should eventually overflow, if you want to see if pump is working you could try what I did by accident, turn engine over with the main cap off on T tower the effect is quite dramatic, but lets you know circ pump is working. FYI my cooling fans start to hit in at 208F and rapidly bring it down. Drove home yesterday 6hrs 375mls and monitored temp all the way Hwy consistent at 202F with little fluctuation.
Jeremy

 

+1 with Richb. Did you replace your pump? I went through the defective water pump scenario. Curiously I could watch the temp drop as I increased RPM at idle. Guess that was from what's left of the blades moving more coolant at higher speeds.

John

 

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Fuses are the same as the above pic , just the the numbering of the pins on the relay module .

Yes on the plastic impeller and the upgraded steel on as the old one breaks .

The following test is quick and simple one that verifies correct fan operation .

Remove the coolant temp sensor .

Remove the O- ring .

Reinstall the connector and turn the key on but don't start .

With a heat gun or hair dryer heat the sensor carefully if all plastic like your engine .

Watch for the one fan to turn on first and as the sensor gets warmer look for both fans to turn on .

You can swap the right fan connector to the left , but have to swap the right fan motor to the left as the wiring may not reach .

This test the fans and control relay module and it's commands from the ECU . To test the AC mode is a different test . And the temp sensor can be calibrated in a ice water or boiling water bath with the sensor completely removed .

Any questions , just ask

 

Thank you for all suggestions. I will report back in a day or two...or three...Had to stay out of the garage today to restore my normally pleasant demeanor.

 

Your first priority is the right fan motor as that is the one to turn on at the lowest temp and can swap fan motors to restore that .

 

I thought they were two speed in the 97 and therefor both came on.

 

Up to the intro of the variable speed fans (2002/3?), the fans are wired in series at 'low speed' and hence run at about half power.

This switches to a parallel arrangement (both fed with 12V from separate fuses) for high speed mode.

 

I have yet to return to the garage...However, the fans come on, albeit at quite a bit higher temperature than specified. The last thing I did before shutting down for the evening was run the temp to a level as high as I dared for a few moments and both fans came on at their highest speed. At a lower temp, it seems that only the left side comes on.

Wondering if the temperature sensor is faulty.

Also interestingly, at one point before I flushed the radiator, it seemed the temp was holding steady...this after replacing the t-stat and water pump. Should have left things alone...

My guess is that almost all of the problems stemmed from having the '98 reservoir attached incorrectly in my '97 and the radiator improperly filling / corroding (but hopefully not too much). The fact that the radiator now fills with significantly more coolant in one pour tells me something was very off.

Fingers are crossed. Will let you know. Thanks again for all the help.

 

The controlling temp sensor is a thermistor that responds the opposite of the old school sensors . A dirty connector on the sensor or ECU and I think there was a connector in between will increase the total resistance of the circuit that the ECU sees . This mimics a cold fluid temp and you may be biased in this way .

 

Tested the car in the daylight today.
Outside temp was ~50 F.
Idle speed only with very occasional revving to 2000.

Right fan came on low at 201.
Both fans came on low at 205.
Both fans switched on to high at 221.
(I) Shut off car at 225.

Inside gauge holding at about the mid point throughout the test.

Took at least 20 minutes to hit high temp.

Reader showed a miss on the fourth cylinder, but I didn't reset it. Believe that I dribbled some coolant on the coil and this code was no longer valid, as the car ran steadily.

After last test and before returning to this test, car didn't want to run more than a few seconds. Replaced fuel filter. Seems to run ok, but I did have a problem with one hot re-start (crossing fingers it isn't the fuel pump, though I am not sure how a fuel pump problem could lead to overheating. Lean condition??)

Thinking about revisiting t-stat. Possibly replacing the temp sensor - or at least spraying it with electrical cleaner.

Suggestions are always appreciated. I'm calmer now, but not sure that will make my car run any better !

Edit...Continued testing....

Temperature seems to have stabilized at 226 F. Also, the heater is starting to work. Guessing that air bubbles/corrosion in radiator is starting to dissipate as result of flushing, putting hoses in correct position and air bubbles bleeding out.

Question: Is this temperature still too high? What might I do to reduce temp further?

 

I forget, did you eliminate the pump? If it's only working with pieces of the blade, it'll look normal til you stress it with high outside temps, stop and go traffic, either plus ac.

It's so common with this year, I don't want to forget it. Heck it might even account for 226 temp.

If this is closed issue pls excuse.

John

 

I think that's it unless someone would like to add to the record.

I would like to know why the car is running at 226 and how to reduce it.

Also would like to know what is the absolute max allowable temp.

However, if 226 is it and that's acceptable, then thread closed successfully. My thought is that the '98 reservoir on the '97 car was at the root of my problems.

To sum up:

In response to Johnken's question, I replaced the water pump. Didn't or haven't checked it with the t-stat tower open, per Jeremys, but pretty sure it is working because of improving health of cooling system. I believe the radiator is clearing itself and the heater motor / core is freeing up. Gosh, I hope so because there is no way I'm going to attack the heater core and I'm not sure I want to argue with the hard to reach heater motor.

Also replaced the thermostat.

Re-routed the reservoir lines per Jaguar TSB 303-15.

Sprayed heat sensor with electrical cleaner.

All hoses except the Octopus have been replaced. Must admit that the Octopus is a little spongy, but - unless it is a problem - it will have to wait until more serious issues are addressed.

Thank you all for your advice.

 

My 97 never got over 215 and usually stayed below 207. I think if I had replaced the radiator the temp would have been lower. If my car were running at 226 I wouldn't drive it until it was sorted

 

Plan is to continue to cycle it to operating temp (maybe 205 or so) at idle or around the block...My gut feeling is that the stuff inside the radiator and heater core is loosening up. Will report if improvement is seen.

Suggestions always welcome.

 

Many have found the heater core plugged and backwashed using a garden hose. Someone may have put stopleak in the system and the radiator core is partially blocked.