Beginning July, I had an issue where I drove about for half an hour and the air would only blow hot, the viscous fan would not spin and the left side of the engine would shudder, thud and hiss every 30 seconds and the engine idle would drop to 400-500 RPM. This would persist until the air would begin blowing cool again and all symptoms would go away.

This issue has continued to date. Sometimes it occurs while driving, sometimes it happens when stopped for a light, but it does not do it all the time.

I brought it to the main dealer and they insisted all was functioning as designed, despite the fact the truck has never had the problem before July this year.

As the problem worsened, I brought it back to the main dealer for the other, probably related concerns I've mentioned in other threads here. Their diagnosis was a failed viscous fan would apparently would also affect whether the climate control worked as well.

Fan replaced and claimed all was in good order.

Started up the truck on the shaded service drive and the air was blowing hot and the newly fitted viscous fan was not running. I left it there for 15 minutes and nothing changed, engine heated up but no fan. Drove about for another 15 minutes with hot air, stopped and engine compartment very hot, viscous fan still not running and all other symptoms present such as shuddering, low RPM, thud, hiss, etc.
Started driving again and air began to blow cold. Stopped, air continued to blow cold, viscous fan was now operational and other symptoms had ceased. I've made various starts and stops for the last couple of hours and all is good so far, but then again this is no different than the last 3 months.

Thoughts?

 

Right, so new AC compressor dispatched over night as there's not much else, could be a compressor valve issue, likely, or clutch issue. Fingers crossed.

 

Well we've run into a problem which is getting more difficult to solve. New viscous fan fitted, check. New AC compressor fitted, check. AC turned on, hot air........ Main dealer further investigating but was told new viscous fan and new AC compressor were the only parts in the system which could cause this problem.

Any experts here care to chime in?

 

Blowing cold air now. JLR tech realised he hadn't pressed the harness connectors together all the way. Now to drive for a few days or so to see if all has been resolved. I will note the engine's a LOT quieter now.