Water Temp Needle

[GlanzaV]

I've just got a new job and it involves a longer commute, and since last week I've noticed a little problem. (I've done a search but would like some suggestions as nothing seems to match my situation)


I start the car and get no beeps from the coolant level sensor or anything (I have had it once a month ago or so but it was very cold ~3deg)

On driving the water temp needle goes up fairly slowly as normal and sits bang on 90deg for about 30min or so along the motorway. I then look down and the water temp needle has dropped to about 75deg, it'll sit like this for maybe 5min then rise back up to 90deg again.


My first thought was perhaps a sticky thermostat but I've never had a VAG car before with all these fancy sensors so I'm not sure it's definately that? I do have and EM light but no VAGCom at the mo (but it's been on since before this prob -- last time I had it cleared by a local mechanic it was overboost and secondary air pump errors.)


Can I assume it's the thermostat? Or should I get someone with VAGCom to check it over?


Cheers

Adrian

 

[Feel]

I would say it's the temperature sender, I had the same on my LCR. This is not the infamous "green top" sensor, it's one that's fitted in the thermostat housing.

 

[GlanzaV]

Hi - A bit more information for you:

On the way to work today ambient temp was 1deg car was frosted over so I had the heaters on HI and blowing out at about the middle setting. My commute is a long motorway journey so I'm mainly off boost (~15inHg vac) at about 70mph (~2750rpm)


Car took a while to get up to operating temp, then same again, temp went down to 70-75deg, but didn't seem to want to come back up. I went on boost for about 30sec to go past traffic, as expected the temp needle started to climb back up slowly, then 5 min later it dropped back to 75deg. It sat like this until I hit some traffic and it climbed back up to 90deg and sat there happily until I reached work.


Does this still sound like the sender?


I popped the connector off the coolant bottle to check the contacts last night but they looked fine. I'm still tempted to say thermostat because I had the virtual same problem with my last car and changing the thermostat fixed it -- but then it didn't have a million and one sensors on the engine to go wrong too!


Any input greatly appreciated.

 

[Feel]

Nope, you looked at the wrong sensor.

If it was the thermostat, it would either overheat (thermostat doesn't open), or take ages to get up to temperature then stay at 90'C once it was up to temperature (thermostat stays open).

It's the sender for the temp gauge.

 

[GlanzaV]

Ok cheers mate. Now just to be annoying, could anyone help me out with part numbers or prices for the temp sender?


Cheers.

 

[Feel]

I can't help there - I got lazy and got the dealer to do it.

 

[ais.smith]

I've had the same problem recently, gauge dropped off down to about 70, waited for a bit, then came back. I've run VAG-COM pretty recently and just had it serviced, so it seems very unlikely to be anything major. Guess it's probably the same temp sender.

Try this site for part numbers:
http://www.vagcat.com/

 

[GlanzaV]

Well I changed the temp sender at the weekend -- It already had the upgraded green sender fitted when I bought the car but decided to replace it anyway since it was an easy job.

The net result -- no changed, on the way to work it did the same thing as per usual. Gets up to temp fine, sits at 90deg for a while then drops to 70deg, after about 15min rises back up to 90deg.

I'm back to my original thought that the thermostat is sticky. Unless anyone else can think of a different reason?

 

[sandro123]

im suffering the same problem, its not be worring me too much as its running cold and not hot. My car is due a service so if i can ill wait til then and see whats up. unless someone suggests otherwise.

 

[SEATCOOBER]

mine has been doing this too, only dropped off to about 80 deg, mine seems to go back up when i turn the blowers off after the windscreen has cleared!!

 

[GlanzaV]

I have only noticed this problem since the end of the summer -- ie when I have my blowers on (usually have them at 25deg blowing at the window about half power.)

I'd rather not have the problem at all though. Going to try and flush the coolant out at the weekend and change the thermostat at the same time. Anyone know how much coolant I'll need to refill?

 

[footlong]

The thing with coolant/ antifreeze is, you can't use too much. i fill up with water, take the top return hose of my bottle with engine running and put coolant in as the water pumps out-end result, i put about1.75l in (i think). make sure you by good quality coolant though, the extra few quid are worth ith in this instance.

 

[stevegti6]

change the temp sender mine done the same should sit on 90 deg common fault acording to the steeler

 

[ttothec]

i had this problem on my old polo 1.4 16v... that turned out to be the thermostat

 

[GlanzaV]

change the temp sender mine done the same should sit on 90 deg common fault acording to the steeler

Well I changed the temp sender at the weekend -- It already had the upgraded green sender fitted when I bought the car but decided to replace it anyway since it was an easy job.

The net result -- no changed, on the way to work it did the same thing as per usual. Gets up to temp fine, sits at 90deg for a while then drops to 70deg, after about 15min rises back up to 90deg.

I'm back to my original thought that the thermostat is sticky. Unless anyone else can think of a different reason?

I've changed the sender mate -- no change! I'm going to hopefully change the thermostat and flush my coolant at the weekend and I'll let you know if there's any changes.