[brumac2]

2005 Passat TDI wagon. 163,000 KM

The temp gauge works has started to act up. It seems to work about 50% of the time and this is reducing. When the car is started it either works or it remains in the "cold" position as in it doesn't move at all for the duration of the drive. If it decides it wants to work it works normally. There are no overheating issues at this point that I am aware of. It seems to be an electrical or connection issue. Any advice on this would be appreciated.

 

[Wav99]

It's probably a bad coolant sensor. This is a very common problem on the ALH's and I wouldn't be surprised if it was the same part.

 

[chittychittybangbang]

Removed double post and moved to mk4 - the Passat is a B5 but it's a 4th generation car so it can be confusing.

A bad coolant temp sensor is the most likely thing. A sticking thermostat is not as likely. If you have a VCDS you could check the coolant temp that the ECU is seeing to confirm a bad sensor and not a bad instrument cluster which is also less likely.

The bad news is that it's at the back of the engine against the firewall. The good news is that it's an easy fix and the clip on the plug is facing you and not the other direction. The plug for the sensor is in a silver heat shield envelope. There's a clip holding the sensor in. Have some G12 coolant handy to replace any lost coolant (do this in a cold engine or else you could be scalded) and bleed the air out afterwards.

Here is an article on bleeding the air out (at bottom)
http://www.myturbodiesel.com/1000q_how_to/b5/coolantflushpassat.htm

Here is a pic of the sensor on the coolant flange. After you remove the plug there's a clip holding the sensor in. The part number is VW# 059 919 501 a (it looks like there were 2 types of sensors and this part number is shared with other TDI). There should be an o-ring as well, wet it with coolant before installing.

 

[brumac2]

Hey Chitty

Thanks for straightening me out on the posting. Just getting my feet wet in all of this.

The photo sure helps to have a clear idea of where the part is but it makes me wonder if a ham handed hacker like me can get my hands in there to find the clips and change this part by brail or would I have to pull the engine to get at it. I will have a look in the day light tomorrow and see what I can do. Thanks again.

 

[Adamgolf]

Try using a mirror for a better look.

 

[brumac2]

I can see the silver insulating jacket you mention but just can't get a clear view of what is what and can't get my hands into the space with enough room to move with any dexterity and vision to start trying to take things apart. The dealership says that it is a one hour job ($120 per hour) plus parts.

The shop says that they usually replace the thermostat at the same time as the temp sensor but I don't know if that is make work project for them or practical necessity. The information you have given me certainly helped me deal with the Service advisor as his first statement was that it was a $500 job and the sensor was a $200 part. When I said it was a $25 part he then back tracked saying he was thinking of a different model.

Is there some trick to making enough space between the firewall and the engine to work efficiently in that area on the back of the block?

Thanks again for all the great ideas and advice.

 

[chittychittybangbang]

I wouldn't replace the thermostat unless there really was a thermostat problem. Again, this is all just a guess based off the sensor actually being bad and causing your problem.

The sensor's plug is a standard VW plug. Pull the locking tab (it faces you so it's not that bad) away from the sensor and wiggle the plug off. Then pull the C- clip holding the sensor off and the sensor should come out. Replace lost coolant and bleed air.

1 hour is reasonable. LOL on the $200 part. Don't be surprised if they charge you $175 worth of coolant

 

[bigshow]

I can see the silver insulating jacket you mention but just can't get a clear view of what is what and can't get my hands into the space with enough room to move with any dexterity and vision to start trying to take things apart. The dealership says that it is a one hour job ($120 per hour) plus parts.

The shop says that they usually replace the thermostat at the same time as the temp sensor but I don't know if that is make work project for them or practical necessity. The information you have given me certainly helped me deal with the Service advisor as his first statement was that it was a $500 job and the sensor was a $200 part. When I said it was a $25 part he then back tracked saying he was thinking of a different model.

Is there some trick to making enough space between the firewall and the engine to work efficiently in that area on the back of the block?

Thanks again for all the great ideas and advice.

In all fairness it must have been a mistake because there's no way the dealer would mark it up an OEM part 8 times and 5 times the labor. Maybe they mark it up 2 or 3 times but no way 8 times. If the book value says this many hours is required that's how much they charge. They can't just drop it from 5 to 1 hour.