Hello,
I have a 90BHP tdi passat with 165,000 miles up on the clock. I noticed sometimes when I start the car the engine revs up to 1200 revs and stays like this for about a minute or two. I also noticed when I wait for the heater plug symbol to disappear from the dash - it sometimes doesnt disappear until 20 seconds, when it should ony appear for about 3 seconds when starting the car from cold.
Has anyone came across this before?
Cheers,
Michael
{Year of car obtained from a forum search - will correct if wrong - DD}
Edited by Dynamic Dave on 06/12/2007 at 18:46
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Sounds like the coolant temperature sensor is up the swanny. Don't know the specifics on this car - there may be more than one controlling ECU / dash gauge / fans. I doubt the fast idle / long glow plug light is too much of a problem, but the fan not coming on when required might be.
On second thoughts, does this engine use a belt driven fan on viscous coupling?
--
RichardW
Is it illogical? It must be Citroen....
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When the engine's really cold it will rev higher for a minute or two, it just helps the engine run better for cold starts. As far as the glow plug light goes, the relay could be faulty. Have you tried the ignition twice before starting the engine? The light should stay on less the second time round as the plugs would already be hot. When was the last time the plugs were changed?
Edited by marty1979 on 06/12/2007 at 16:55
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Michael
I'd be inclined to suspect the coolant temp sensor too.
They're not dear; might be worth a new one on the off-chance - just get a new clip and rubber seal with it.
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Hello,
To answer your questions:
1) Not too sure about the fan belt - all i know is it is a belt driven fan belt and ive never heard it coming on while the engine is off!
2)Tried turning off the ignition twice but still the light stays on a bit longer than it should and the car can still rev up (the light disappears after i start the car as it should)
3) I have never changed the glow plugs ever
So its either:
a) need new coolant temp sensor
b)new glow plugs (although I have no problem starting the car it turns once or twice and then it starts no problem)
c)new relay
Where could I get my hands on a new temp sensor?
vagparts.com is a good site?
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Hi Screwloose,
I was reading this website here:
www.taligentx.com/passat/maintenance/coolanttempse.../
Here it says:
Symptoms:
"The coolant temp sender has failed if the coolant temp gauge in the instrument cluster lives up to VW's parts reputation (Varies Widely). If the gauge informs you that the engine is stone cold while you're running 85 mph, it's time to replace the sender".
Going by this info, my temp gauge seems to be working ok e.g. the needle stays in the middle when I have been driving it after 15-20 mins and stays in this position. It ticks over fine most of the time. If I drive the car for an hr (thats about 30 miles), then turn it off and drive it again after 3 hrs , the engine revs up a bit and can go to 1,300 or 1,400 rpm then goes back down again.
Based on this do you still think its the temp sender thats faulty?
Cheers,
Mike
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The gauge has a separate thermistor to the engine management one.
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Had similar problem myself, engine revved up and down wildly on start up.....new coolant temperature sensor was the answer!
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Thanks guys,
Ive ordered the part! My final question-where around the engine can I see the temp sender?
Is it under the plastic cover that hides the engine?
or
do i need to open the plastic housing in the corner with the umbrella symbol (driver side of engine)
THANKS!
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carlover
You will need to remove the cover.
I hope the new sensor comes with new seal and clip? It's in the water elbow on the N/S end of the cylinder head and you'll need a litre of anti-freeze to top-up with afterwards.
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Hi Screwloose,
It comes with a seal but not the clip! Ordered it on vagparts.co.uk!
Sounds like I can do damage if I replace it myself. Why do I need too add coolant?
Does fluid leak out after pulling up the temperature sender?
Maybe i should go to a garage!
Thanks!
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With practice you only lose a few tablespoonfuls; but having some top-up is a wise move. The clip is optional; be careful removing it if you don't have a new one.
Not a bad job; just go steadily. Under one minute for a pro.
Edited by Screwloose on 10/03/2008 at 18:02
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Thanks Screwloose!
Fitted new part and problem is gone!
Cheers,
Michael
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