Hello,

Occasionally my ZF 5 speed has gone into 'protection' mode (tends to happen after coming off the motorway after about a 70 mile run and then 5 or so miles of A & B roads). Had the transmission fluid changed but this still occurs about 1 in 5 journeys.

Yesterday, after doing about 5 miles on a 'fast' A road, I had to do about 10 miles on slow, winding B roads - the transmission went into protection mode, then (for the 1st time ever) the 'transmission overheat' message popped up on the dash.

I pulled over and my IID Tool showed the transmission fluid temperature as being over 150 celsius. I let the transmission cool and then continued home without further incident.

This morning the outside air temperature was about 18 celsius, the vehicle had been left standing overnight, I took a transmission fluid temperature reading from my IID tool which showed 38 degrees celsius (so I'm assuming the transmission temperature sensors could be over reading by about 20 celsius ?). Hence I'm wondering if there could be a fault with the transmission temperature sensors rather than the common issue issue of blocked cooler or worse case - transmission fault ?

Grateful thanks in advance for any replies.

more likely a clogged trans cooler and / or lower rad. Very common No7 - 2003 V8 Vogue

I'd start with a temp reading at idle from cold. Mine stays in that 41c range quite a while. We need RRphil to jump in here. I believe normal temp is 100c so 150c is bad. How many miles? How old radiator? What is engine coolant temp and radiator temp? Best to check live values on highway and secondary highways. Also buy the thermostat retrofit to drop overall temps.

Yes, a faulty sensor is definitely a possibility, though the transmission fluid temperature should be about the same as the engine coolant temperature (100°-110°C) so it would have to be reading 40° or 50°C too high to activate the overheat message. You really need to calibrate the sensor signal somehow. Do you have one of those laser infra-red thermometer thingies that you could point at the transmission’s metal sump pan when it's reading hyper-hot?

The diagnostics kit (and the transmission ECU) measures the resistance of the PTC sensor in the transmission wiring loom, which sits in the fluid

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Really grateful for the prompt replies.

Drove (carefully) a 150 mile round trip today (75 miles each way). IID tool showed transmission fluid 130 degrees after 1st leg of journey, 4 hour cool down then read 120 degrees when I got home. If I hadn't had the IID tool I'd not have had any indication today that anything was wrong.

IID tool indicates that engine temperature is OK, as is radiator temperature (only replaced last November).

L322 currently has covered 141,000 miles and had 'gearbox kit', new torque converter and 'bearing' fitted under previous ownership in 2013, 102,000 miles - apart from that, the receipt only states 'Remove Gearbox, strip down, replace parts listed, refit (£1322.76).

I'm going to get the transmission cooler and thermostat replaced next week, along with new filter and fluid. Do you recommend new transmission to transmission cooler hoses? If so, grateful if someone could recommend a supplier.

Again, ever so grateful for the advice.

Cheers,

Eddie

If you have a new radiator then that is ruled out. How do you know it isn't just the transmission cooler thermostat? RRPhil will know if they fail opened or closed. If no one knows I'd just do the transmission thermostat first and see how it changes. Mine cracked from age and was replaced. Plus they are relatively cheap.

Get this sorted yet?

Yes I replaced my transmission cooler which was almost blocked.Radiator was only a few years old but when I had temps read on live feed it was flicking up and down which pointed to the temp sensor also.Got mine from Jpat transmissions for £100 there is a YouTube video which shows you how to fit

I think Rangeyman has replied to the wrong post.

No, not sorted yet. My excellent mechanic is collecting the L322 tomorrow, will test transmission fluid temperature sensors as advised by RR Phil.

Also had delivery today of transmission oil cooler, thermostat, mounting plate, transmission oil, filter and gasket. So hopefully will have issue sorted next week.

Also being done - front and rear diff oil, transfer box oil and engine oil & filter & MoT.

Wrong post??? When you have your cooler changed ask for it back and stick a hosepipe on the water side it should run through clearly mine just sprayed in my face.That will just confirm wether it was a problem.If I remember it rightly the temp switches around 110 deg so if you are getting readings of 130 it is the temp gauge if the cooler is working fine.If you are changing everything it is not a problem but it is always nice to know what is the main culprit.

My sincere apologies Rangeyman, I misread your reply.

Was it hard to replace the temperature sensor loom?

Hope you have a great weekend!

http://www.roverparts.com/resources/videos...ing-light/ A good video here which shows you how it is done only for me the rear speed sensor retainer screw was incredibly tight and is in a very difficult place I needed a special small ratchet screwdriver to get it out and almost thought it wasn't going to come out at all.Had to laugh when it does not show him taking it out.