Hi Everyone

Long-time lurker but first post.

Car is a 2002 3.0 auto. A few months back the dreaded fan control module failure happened. I'm still looking for a decent old-type replacement. To prevent the fans from continuously running in the meantime, my indy rigged up a temperature sensor switch attached to the rad hose. The best we could get was the fans now kicking on at an indicated +/- 85 degrees celsius according to the OBD test menu on the odo. During about-town operation the engine temperature is always between 86 degrees celsius and 88 degrees celsius now according to the obd readout (fans basically running continuously when engine is warm and on). I have not managed to check highway speed readings yet. Temp. dial is in the correct place and does not budge when warm.

I'm concerned if this means the engine is running too cold and causing inefficient combustion. No discernible drop in economy and car seems to have full performance. What confuses me when I think about it is what temperature the car would be normally running at on the highway if no fan issue. In other words the fans surely mimic highway driving conditions but around town (high speed airflow would be =/> than fan output?).

Are these temps fine? I've looked at other threads and temp values seem all over the place.

I'm also attaching a few pics of my exhaust ends which are starting to show some rust. This could be because I was laid up for a few months after surgery and the car was not washed in all that time and used infrequently for short trips, but I hope it is not a sign of incomplete combustion.

Advice will be appreciated, thank you.

 

Which I suspect is your thermostat rating, so the engine should always run at least that warm.....which would be considered 'fully warmed up' in most any car and the engine management system calibrated for that temp. I doubt that higher temp would bring any increase in efficiency. But, alas, I have zero X-type experience so take my words with a grain of salt.

The rust in the tailpipe is probably nothing to be concerned about. Water is a natural byproduct of internal combustion. Lack of use means the exhaust system doesn't get hot enough to burn away all the water so the innards become rusty.

Cheers
DD

 

Extracts from the Jaguar workshop manual

The thermostat is located in a housing in the upper coolant hose and allows rapid engine warm-up by restricting coolant flow through the radiator below 82°C (180°F). The thermostat also assists in keeping the engine operating temperature within predetermined limits. The thermostat begins to open at 82°C (180°F) and is fully open at 93°C (199°F).

The cooling fans are operated at slow speed when the engine coolant temperature is at 95°C (203°F) and are operated at full speed when the engine coolant temperature is at 105°C (221°F). A coolant temperature between these temperatures will cause the cooling fans to be operated at a speed which is proportional to the engine coolant temperature.

Note that the fans should always be running when the AC is on.

 

Guys thanks for the helpful info. Can there be any harm if the thermostat is not fully open due to fans preventing the coolant from going past fully open temperature?

Assuming the thermostat is kind of regulating things at approx. 87 degrees on my car, does this mean that combustion temps are kept ideal?

 

I can't see how or where any harm would be done.

My assumption is that the thermostat is rated at 88º....as that is a common thing. Since you're consistently running a bit below that rating....albeit just barely and still within the stated open-close range of 82º-93º...it might be that your thermo is a bit weak. Replacing it might bring the coolant temp to a higher level within that range.

I have doubts that doing so would result in any measurable or tangible increase in efficiency but there's nothing stopping you from giving it a try !

Cheers
DD