Running Hot

[zaph]

TBH, thought the issue had been solved - see drinking water thread.

But again the, dial shot up to H on the way home from shopping this morning. Water/antifreeze was topped up at the begining of the week and levels have been fine throughout, havingh done around 70 miles or so, as has the temperature gauge. I cannot see any problems with hoses, or radiator - leaks etc, but I willl not discount this.

I'll check the current levels in a mo' .

So, what is it folks?

(Bearing in mind I am more familiar with Saabs)

• In need of a reverse flush through - is there a different procedure for this, please?
  
• Dodgy thermostat?
  
• Failing secondary fan switch - haven't seen or heard it working - where is it and procedure for checking, please?
  

Where does the overflow pipe from the expansion tank drain to - I have been unable to trace, fully? On the occassion she has dumped coolant, it has been very difficult to trace where it has come from.

Thanks in advance!

[randyreindeer]

Are you filling it through the expansion tank or through the filler on the Engine?

[zaph]

Are you filling it through the expansion tank or through the filler on the Engine?

Expansion tank.

[widnes_is200]

might be worth checking ure thermostat, take it out and boil in a pan , then ulle see if it opens all the time,

[MacRS200]

Does the overheating only happen when running around town?

If so I would suspect the fan or temp sensor, try running the engine at idle and see if the fan starts as the temp goes up.

[Mybikesacx500]

I remember years ago reading about similar symptoms, and it turned out to be a failing radiator hose that had delaminated internaly, and a flap of rubber occasionallly blocked the hose. OK, so thats unlikely, and hose manufacture may be different now, but thought I'd mention it, in case no other cause found...

[zaph]

Thanks for your replies.

Of course, Sod's law, the problem is intermittent!

I checked the coolant level, which was fine, and between the marks, before setting off yesterday morning for 10 mile trip down to Bedminster, yesterday, country lanes, and a bit of urban work - fine, until I got to Portway, which is a 50 mph road, and the temperature continued to shoot up reaching H, and fell back a click, but more or less as soon as I pulled into a Car Park, the temperature indciation dropped dramatcially to where it should be - basically, on the car, the needle points dirctly to 7 on the Rev counter. The trip home, same route, around 10 minutes later was uneventful! Drive to work yesterday afternoon, urban traffic, two hours later, - admittedly a short trip of around 3 miles - again fine. Long trip home - on purpose - roads clear and a typical 40 -50 mph 7 mile journey, again fine!

And again, this morning, cooolant levels as they were yesterday and 5 mile trip to order a thermostat - always handy to have a spare in any instance - fine - trip back fine!

Thanks for the info, on the delaminating hose/s.

As I stated earlier, I've never seen or heard the secondary fan kick in!

[sparkyhx]

Thanks for your replies.

Of course, Sod's law, the problem is intermittent!

I checked the coolant level, which was fine, and between the marks, before setting off yesterday morning for 10 mile trip down to Bedminster, yesterday, country lanes, and a bit of urban work - fine, until I got to Portway, which is a 50 mph road, and the temperature continued to shoot up reaching H, and fell back a click, but more or less as soon as I pulled into a Car Park, the temperature indciation dropped dramatcially to where it should be - basically, on the car, the needle points dirctly to 7 on the Rev counter. The trip home, same route, around 10 minutes later was uneventful! Drive to work yesterday afternoon, urban traffic, two hours later, - admittedly a short trip of around 3 miles - again fine. Long trip home - on purpose - roads clear and a typical 40 -50 mph 7 mile journey, again fine!

And again, this morning, cooolant levels as they were yesterday and 5 mile trip to order a thermostat - always handy to have a spare in any instance - fine - trip back fine!

Thanks for the info, on the delaminating hose/s.

As I stated earlier, I've never seen or heard the secondary fan kick in!

Lets start with the easy stuff

- by the sounds of it your not loosing water - so that rules out head gasket, and general leaks. but keep an eye on it

- air lock - quite common cause especially if you have filled it up recently -

- check the RAD for any cold spots when wam - this wouild indicate a blocked RAD - quite possible but probably wouldn't be intermittent

- check thermostat - your doing that.

- ensure fans kick in ok - if not then thats your problem

- guage/sensor/sender dodgy - less easy to check - auto electrician but the intermittent nature makes that hard

[ManicMark]

Hi isnt the fan on all the ls 400 range constant run off the belt not electric is on my mark4

[ManicMark]

Hi reading through the posts do your thermostat they do stick intermitantly, see how it goes from there.

[zaph]

Hi isnt the fan on all the ls 400 range constant run off the belt not electric is on my mark4

There is a second fan offside, placed in front of the rad on my LS400 -1992.

Thanks for the replies - symptoms have not returned since Monday - despite trying!

I too have thought of the air lock route - which would explain, if the secondary rad switch is ok, it is not cutting in.

I'll plan to do a reverse flush from the thermostat housing.

I'll keep everyone posted.

[Steve ( West Mids )]

On thee secondary fan try tracing the wiring back to the block ( I assume that is where the sensor is and disconnecting the wiring from the sensor and shoorting across it ( if 2 wires ) or to earth if it's one wire and seeinf it the fan comes on. If not then I would look for the fuse. If it does come on then suspect the sensor.