frugality
Top Post Dawg
This is just an FYI post for anyone replacing a coolant temperature sensor.
Long story short, my 2000 Golf TDI developed a problem where the temp gage needle wouldn't go up to the center 190 mark. Occasionally it was a little shy, and a few times it was a full two hashmarks low on the gage. I suspected a bad thermostat, because I've heard that VW thermostats are designed to fail in the 'open' position, and therefore err on the side of being too cool. However, in doing some searching here, I found that the temperature sensor may be the problem. Seems that the sensors were more prone to failure than thermostats are.
One suggestion came up on a thread that you didn't have to drain the coolant -- just pull the old sensor and be prepared to plug in the new one quickly as coolant starts to come out. This worked O.K., but I want to post a warning. I pulled the old one, and quickly jammed in the new one, only to find that the old one that was now in my hand didn't have the O-ring on it. It had stayed inside the casting, and I'd jammed the new one in with its new O-ring, so now there were 2 O-rings in there. So I had to pull it out again and fix things, and meanwhile I dumped a bunch of coolant. Still, with all that, I didn't lose enough coolant to have to top up right away. The level went from close to the sensor on the reservoir down to just above the hatched 'minimum' area.
The basic procedure:
* Let the engine cool. I waited 2 hours from being hot, and the coolant was bathwater warm. (and my hands did get bathed)
* Remove engine cover and accordion hose between MAF sensor and intake downpipe.
* Open the cap on the coolant reservoir to release any pressure in the system. Then close it again.
* Unplug the old sensor. This was kind of a bugger. I ended up getting it loose by putting a small screwdriver into the area where the release tab is, and then twisting the screwdriver to push on the tab. Having a look-see with a small mirror beforehand is helpful.
* Plug your new sensor into the wire harness.
* Remove the plastic 'C' clip that retains the old sensor. Be carful not to drop it, because it's plastic and you can't fish it out with a magnet.
* Hug your engine. With one hand you'll remove the old sensor, and with the other hand you'll plug in the new sensor, as coolant starts to pour out. You may have to fish out your old O-ring like I did, in which case you'll loose a couple cups of coolant.
* Replace plastic C-clip.
* Check and add coolant if necessary.
* Reinstall accordion hose.
* Start engine and check for leaks.
* Pat yourself on the back.
I'll have to watch for the next few days, but this seems to have fixed the problem. Twice now the temp gage goes right up to 190 and stays there. It's nice to have a quick, cheap fix.
Also as a side note, my 2000 Golf was made in 12/1999, so it should have had the blue, square temperature sensor. Later models have a rounded green sensor. However, mine was black, and was rounded -- sort of a D-shape. Maybe mine was different because my car was German-made.
My local dealer quoted $34 for the sensor, which they had in stock. I got mine for $14+shipping at tdiparts.com. I also got an extra O-ring for $1, and that was a good idea. I lost one down below the engine when I fumbled around removing the new sensor to get the old O-ring out.
***Edit to add removal/installation of accordion hose to procedure.
Long story short, my 2000 Golf TDI developed a problem where the temp gage needle wouldn't go up to the center 190 mark. Occasionally it was a little shy, and a few times it was a full two hashmarks low on the gage. I suspected a bad thermostat, because I've heard that VW thermostats are designed to fail in the 'open' position, and therefore err on the side of being too cool. However, in doing some searching here, I found that the temperature sensor may be the problem. Seems that the sensors were more prone to failure than thermostats are.
One suggestion came up on a thread that you didn't have to drain the coolant -- just pull the old sensor and be prepared to plug in the new one quickly as coolant starts to come out. This worked O.K., but I want to post a warning. I pulled the old one, and quickly jammed in the new one, only to find that the old one that was now in my hand didn't have the O-ring on it. It had stayed inside the casting, and I'd jammed the new one in with its new O-ring, so now there were 2 O-rings in there. So I had to pull it out again and fix things, and meanwhile I dumped a bunch of coolant. Still, with all that, I didn't lose enough coolant to have to top up right away. The level went from close to the sensor on the reservoir down to just above the hatched 'minimum' area.
The basic procedure:
* Let the engine cool. I waited 2 hours from being hot, and the coolant was bathwater warm. (and my hands did get bathed)
* Remove engine cover and accordion hose between MAF sensor and intake downpipe.
* Open the cap on the coolant reservoir to release any pressure in the system. Then close it again.
* Unplug the old sensor. This was kind of a bugger. I ended up getting it loose by putting a small screwdriver into the area where the release tab is, and then twisting the screwdriver to push on the tab. Having a look-see with a small mirror beforehand is helpful.
* Plug your new sensor into the wire harness.
* Remove the plastic 'C' clip that retains the old sensor. Be carful not to drop it, because it's plastic and you can't fish it out with a magnet.
* Hug your engine. With one hand you'll remove the old sensor, and with the other hand you'll plug in the new sensor, as coolant starts to pour out. You may have to fish out your old O-ring like I did, in which case you'll loose a couple cups of coolant.
* Replace plastic C-clip.
* Check and add coolant if necessary.
* Reinstall accordion hose.
* Start engine and check for leaks.
* Pat yourself on the back.
I'll have to watch for the next few days, but this seems to have fixed the problem. Twice now the temp gage goes right up to 190 and stays there. It's nice to have a quick, cheap fix.
Also as a side note, my 2000 Golf was made in 12/1999, so it should have had the blue, square temperature sensor. Later models have a rounded green sensor. However, mine was black, and was rounded -- sort of a D-shape. Maybe mine was different because my car was German-made.
My local dealer quoted $34 for the sensor, which they had in stock. I got mine for $14+shipping at tdiparts.com. I also got an extra O-ring for $1, and that was a good idea. I lost one down below the engine when I fumbled around removing the new sensor to get the old O-ring out.
***Edit to add removal/installation of accordion hose to procedure.
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