Strange engine temperature guage behaviour

Sugar Free · 15 Oct 2009 at 13:54

Lately my engine temperature guage has been acting a bit funny. It'll sometimes drop to the baseline (50 degrees) and shoot up to the normal range (90 degrees) again after a while.

It doesn't go above the normal range.

Any ideas? Broken temperature sensor? Broken coolant system?

The car is a mk5 golf tdi.

Dangerous Dave · 15 Oct 2009 at 13:57

Could either be the temperature sensor or the thermostat being stuck open. The Golf has several temperture sensors around the cooling system but only one feeds the gauge a garage with Vagcom/VCDS will quickly be able to tell you if the temperature sensor is faulty.

My money would be on the thermostat personally.

cm1179 · 15 Oct 2009 at 14:00

my mk4 golf used to do exactly the same, i wouldn't worry about it

paradigm · 15 Oct 2009 at 14:10

cm1179 said:
my mk4 golf used to do exactly the same, i wouldn't worry about it

My leon does exactly the same. It is usually a duff sender.

Sugar Free · 15 Oct 2009 at 14:16

Hmm, so it's not really worth bothering about then?

Matt82 · 15 Oct 2009 at 14:19

find out if its getting hot or cold or not then see what happens

if the gauge isnt working, how willy ou know if your car is abuot to volcano on you?

dalin80 · 15 Oct 2009 at 18:08

VW temp sensors are made of cheese so it wouldn't surprise me ifg its on its way out.

could also be a sticky thermostat, might as well have them both done to save having to bleed the coolant system twice.

*Moangroan* · 15 Oct 2009 at 18:59

I would go for the coolant temp sensor. Your car I think has two. A black one to the right and backside of the block and a grey one near the bottom of the rad. I would opt for the black one. Probably about £25 from vw.

Fuzz · 15 Oct 2009 at 19:24

the sensor for the gauge is usually a "one wire" sensor unit if that helps.
There will probably be at least one more.
One so the ECU knows what temperature the coolant is at (and this will be a two wire sensor) and possibly one for the radiator fans if the ECU doesn't control them internally.

Dangerous Dave · 15 Oct 2009 at 20:02

There are four temp sensors in MK5 Golfs cooling system, they monitor the temperature leaving the block, entering the radiator and leaving the radiator and the one for the dash/ecu which doubles up as the temperture of coolant going into the block.

I have heard of a few diesel mk5 Golfs needing the thermostat replaced as it has stuck open.

dalin80 · 15 Oct 2009 at 20:50

Scubascorpion said:
the sensor for the gauge is usually a "one wire" sensor unit if that helps.
There will probably be at least one more.
One so the ECU knows what temperature the coolant is at (and this will be a two wire sensor) and possibly one for the radiator fans if the ECU doesn't control them internally.

very few are one wire anymore as more and more gauges are fed by the ecu rather then there own sensors.

Fuzz · 15 Oct 2009 at 21:15

dalin80 said:
very few are one wire anymore as more and more gauges are fed by the ecu rather then there own sensors.

Fair enough, Golf III is one wire.

But go put this into google "web" and click on the first picture suggestion.

"golf IV wiring diagram"

One yellow wire ! (assuming that a "KLR650" is some sort of Mkiv golf of course, I have no idea.

)

Bluelion · 15 Oct 2009 at 22:17

Had the same thing on my mk4. New sender and voila all fixed, not that expensive and easy to do on the mk4 to boot.

Happy · 15 Oct 2009 at 22:34

paradigm said:
My leon does exactly the same. It is usually a duff sender.

As does my Ibzia, I was hoping it was something that can be ignored.

Matt82 · 15 Oct 2009 at 22:54

my friends mum has a mk4 v6 4mo. the temp guage hadnt been working for a while then one afternoon whilst sat idling on out driveway it volcano'd, no fans on, it had roasted itself. i suppose with a gauge you might have seen, but being a woman she would have prolly ignored it anyway

topbanana · 16 Oct 2009 at 09:04

Could be a number of things. Worth checking as it might be the water pump

[TW]Fox · 16 Oct 2009 at 10:14

Happy said:
As does my Ibzia, I was hoping it was something that can be ignored.

Why would you want to ignore it instead of fixing it :confused:

Happy · 16 Oct 2009 at 16:56

Because if I was going to be spending any money on it, there's a very long list of stuff that's more important than a gauge which sometimes doesn't work.

*Moangroan* · 16 Oct 2009 at 17:22

Happy said:
Because if I was going to be spending any money on it, there's a very long list of stuff that's more important than a gauge which sometimes doesn't work.

TBH the temp gauge is an engine saver.

Happy · 16 Oct 2009 at 17:44

But all it does is drop down to low for a couple of seconds then rise back to normal, it does this maybe twice a week. If it's gets more serious where it doesn't move etc, then I'll get it fixed. Basically I loath spending anything on it as I'm saving for something else... reliable.