S90 overheating issue

[Pothole]

Hi all, I recently purchased a 1998 S90 Luxury Edition with Nearly FSH and 116000 miles up. The temp gauge went fully into the red on the way home the other day so I immediately thought 'thermostat'. I replaced the thermostat this morning and at first it seemed to be cured but after about 5 minutes of driving the needle is once more going to the red...it is a little inconsistent though (wavered between normal (straight up and down) and in the red a couple of times)...the other odd thing is the top hose gets hot but the bottom one is hardly warm? What's the likely cause? Blockage somewhere?

Edited by Pothole on Saturday 15th January 13:58

[mikealder]

I can't remember what type of fan is fitted to that model, if its electric then I would expect the top and bottom hoses to be the same temperature until the fan kicks in, if its an engine driven fan (even with a viscous coupling) the bottom hose will generally feel much cooler than the top hose with the engine running under no load (car sat still).

If the temp gauge is wandering about there are two probable causes:

Poor wiring contact most likely on the dash PCB behind the instruments
Broken temp sender which is easy to swap out

Mike

[Pothole]

hmmm. Fan is kicking in and going to high speed, but that's probably in response to the temp sender which is also causing the gauge to go to red...top hose is not so hot you can't hold it which I would sort of expect if it really was getting that hot...wonder where the sender is.

ETA: Thanks, btw!

Edited by Pothole on Saturday 15th January 17:31

[morgrp]

is the heater working? and is the temperature rising when under load then dropping slightly when backing off?

[Pothole]

Heater is working fine, temp gauge staying high, except for a few wobbles..it's the temp sender according to local mobile mechanic. £55 fix if he ever comes back!