Hi all, I'm new here and hoping there is someone out there who can help!

I've had my 1999 XJR for a few years and on one long trip, it overheated. Topped it up and no further problems for six months. Then the same issue again and it became more and more frequent.

I was at one time told it was head gasget but its not the case.

The coolant blows out of the overflow from the header tank.

I've flushed the system, checked the water pump, replaced the thermostat and pressure cap and checked all hoses.

It seems better but still not right and now the fans don't seem to cut in!

Any ideas would be appreciated!

 

Hi Paulevans22:
Welcome to the forum! Be sure to check in at the New Members section to make the proper introductions.

Others will have more technical knowledge, but I can tell you from very recent personal experience that an original water pump on these cars will wreak the havoc you are describing. Assuming they used the same water pump on the XJRs as the regular cars, the impellers were made out of plastic and just disintegrate over time. The outside may stand up to inspection, but inside it isn't generating enough flow for the engine to keep cool, whence your overflow. Trouble is, if you let these cars overheat, it will wreck the head gaskets. Perhaps you've already swapped the water pump with one with metal impellers, but it was worth a mention. You can certainly read more (as I have just done!) in the archives…
Best of luck!
Scott

 

Thanks Scott,

I did take the old pump out and gave it a good inspection but it all seemed to be in good order. I did read up on the pumps falling to bits. Do you know if it is possible that the impellers can wear down without breaking up?

Paul

 

Hi Paul,
If the fans are not cutting in then either things are fine or you are on borrowed time.
Check the temperature sensor, disconnect and place a jumper in the plug to see if the fans come on. If not, go back to the relay and fuses. If it does then you probably have a faulty sensor.

As for the pump, yes it is possible for the impeller to wear away over time. By the way, OEM jaguar pumps all have plastic impellers as the TSB confirms.

Hope this helps,

On a side note, where in France are you.

 

The recommended way to rule out a blown headgasket when there is coolant blowing out of the system is to do a exhaust gas test. It is a device somewhat like a turkey baster containing a liquid which changes colour in the presence of exhaust gases. This is held to the neck of the header tank.

With regard to the fan system, it may be defective or it may not be sensing the temperature.

How is the temperature gauge?

The unfortunate part of the temperature detection on a AJ27 SC is that the temperature sensor is in a high part of the system. If the coolant is low, it cannot sense the temperature because the coolant is not flowing past the sensor. Therefore, you have to completely bleed the cooling system. This is not hard, but it takes time and attention to detail. You will likely have to do it several times to get the airlocks out.

Can you see coolant flow in the header tank through the filler opening when the engine is running? Start with the engine cold and cap off so that coolant doesn't come rushing out because you opened a pressurised system.

 

Thanks Jim,

Looks like I'm in for a busy weekend and will try that out. I did check the fuses but didn't think about the sensor.

I'm in the middle of Brittany, been here 12 years and wouldn't change it now. Especially when the car is up and running again with not much traffic here!

 

Plums is correct about the coolant level and the temp gauge. If the level is a little low the temp sensor will not get a correct reading, and the system needs a burp. I had a problem with cooling hoses blowing off, and it was due to the fans not coming on. My problem was just a fuse, but it did cause me a lot of heartache before figuring that out.

 

Thanks Plums,

The first thing I did was to have the gas test and there was no exhaust gas present. Temperature gauge is reading slightly above normal when it starts to blow but the coolant is not boiling.

There is a flow in the header tank and I've been pretty thorough with bleeding the system including the supercharger unit.

Looks like as with Jim's message, the sensor could be an issue.

Thanks again

Paul

 

The temperature gauge on these cars is just a glorified idiot light.
It works as normal from cold to operating temp. (middle of gauge), then doesn't move again until temp hits about 215 F, which is usually too late. A number of members have fitted the Realgauge kit, which is sold by a forum member; look up thejagwrangler on the net.
Does the problem occur in traffic, or on the highway?

 

If the coolant is not boiling* yet you are blowing coolant out of the overflow where would you suggest that pressure is coming from?
Sure sounds to me like a failed head gasket over pressurizing the cooling system.
Do you have any rough running issues when starting a cold engine? Steam from the exhaust?
* You could have a localized hot spot(and boiling you'll not see) somewhere in the cooling system, either from air in the system or a restriction.

 

In addition to failed head gasket, it could be a sticking thermostat.

Just because it's new doesn't mean it's working properly.