Replace the pressure cap. Mine gave me a lot of grief. Also be sure your hose to the overflow tank is good. If it leaks the back suction created during cooling should draw coolant ffrom the overflow tank into the expansion tank, but if the hose leakss, only air will go back into the expansion tank. Finally, replace the coolant sensor. They are cheap, and notoriously failure prone. I like to keep a spare on hand.

John Rodgers 88 GL Driver

Marc Perdue wrote:

> Hi all, > > I've also been battling the low-coolant sensor issue. I was going to > get the nearest dedicated VW mechanics to bleed the cooling system, but > ran into a problem. These guys, C.J. Buggs in Fishersville, VA, had > somewhat jerked me around about my transmission when I got it, but they > finally got it in and it's been working fine, so I thought I would give > them a second chance. Good VW mechanics are not easy to find after > all. I set up an appointment to get the cooling system checked over, > took the van to them and left it first thing in the morning. Being as > they're located a good 45 miles from where I work, I was not able to go > to work while the van was being worked on (no transport back over the > mountain), but hung out with a friend instead. After not getting a call > from them most of the day, I went back at 2:30 only to find that they > had gotten tied up on a major engine problem and asked if it was a major > inconvenience for me to leave the van overnight. I told them it was a > major inconvenience for me to come there to begin with and that I > couldn't leave the van, so I left. > > Having made that short story long, I found that if I left the van to > cool overnight after the low-coolant sensor came on, the expansion tank > would depressurize and I could top it off with coolant/water. I did > this several times and the problem seemed to have gone away. It's come > back, but differently. Now when the sensor comes on, the level in the > expansion tank is not actually below the bottom of the sensor. Simple, > right? Just replace the coolant-level sensor. I'm going to. The funny > thing is that the light comes on after I go over a decent sized mountain > with a long grade up. Weird, hunh? Another thing that's different is > that when I had the problem before, even though the coolant was getting > low in the expansion tank, I would see changes in the level of the > coolant in the reservoir. Not anymore. I'm thinking that I also need > to replace the expansion tank pressure cap and probably the hose that > connects the expansion tank and reservoir in addition to the > coolant-level sensor. I haven't seen any signs of a coolant leak except > for right after my new tires were put on. That's been a few months > ago. At that point there was a small leak in one of the hoses right > over the spare tire. Apparently the larger spare caused one of the hose > connections to work loose a little. I tightened that up and haven't had > a leak since (that I could find anyway). > > My question is if you all think I'm on the right track replacing the > coolant-level sensor, the pressure cap and the connecting hose . . . > After the recent windshield washer pump purchase that was totally > unnecessary, I just wanted to try to avoid more such purchases . . . > > Thanks in advance, > Marc Perdue