Water temp. sender failure... ONLY at high temps?

[T350 Brad]

As some of you will know, I picked up my T350 on Saturday...

Car was returned to the garage on Monday as i'd got Water temp (and Oil temp) sender failure messages, despite, I believe, them being the 'updated' senders.

Dealer replaced both water temp senders, and oil temp sender, and returned the car...

... however, since getting it back, on the two journeys i've done where water temp has gone above 90(ish) I get the sender failure message

Like I say, this only seems to happen when temps get high, if they stay below 90 (i.e. on short / quick journeys) it's fine... has anybody got any idea what's causing this, should I have them re-replaced?? The reason why I'm concerned is that I want accurate readings especially at high temps so I can make sure fans are operating correctly (when dealer did the replacement they checked using diagnostocs and fans were fine) and avoid risking damaging the head gasket etc.

Any ideas / similar experiences gratefully received.

Thanks

Bradders

[VARLEYHYD]

Replacement sensors could be old stock, which did have issues. The water temp sender is at the top of the engine head under the airbox ,because of where it is I've heard they can get air locked causing the fault. Oil temp should be no problems but if the connection is poor or the wire is severed the change up lamps will default to 4000rpm

[anonymous-user]

Do you have the later header tank modification?

On my T350 I used to get this and I am sure it was down to air in the system which was a B*TCH to get rid of.
Basically it was explained to me that air/steam would hover around the sensor and screw the system. Always used to happen when slow/stationary, OK when travelling.

Doesn't happen on the Sag which has the later coolant system.

May be talking balls, but there you go.

sw

Edited by anonymous-user on Thursday 8th March 16:12

[T350 Brad]

It's an '03 car with the expansion tank modification!?

Mine's exactly the same, happens only when in traffic and temps rise... but, i've been told air was bled from the system on Tuesday when the new sensors were fitted...?

[anonymous-user]

I was told the same by dealer on several occasions.

took a decent indie an hour of patient messing around to sort.

sw

[T350 Brad]

Cheers for the heads-up...

... what was found to be the problem / solution in the end??

[anonymous-user]

bleed THOROUGHLY. There will probably be much more air in that you think.
As usual a bit of a pain in the arse.

Problem solved.

I was going to get the tank mod under warranty but swapped for a Sag.
No more problem!