I have a 1988 N/A Mark III. The radiator fluid overflow sensor goes on every 2-3 weeks and I need to add maybe a pint or 2 of fluid. I checked and changed the oil several times and it doesn't have one spec of condensation or water in it. The temperature gauge is spot on. The engine runs perfect and there are no issues at all. No leaks, no nothing. Nothing coming out of the tailpipe either. I also don't see any wetness near the waterpump and it isn't making any bearing noises or anything. The car has 100K on it. I have owned and have been driving the car for over a year with no problems at all. Any suggestions as to where my radiator fluid is going??
I am thinking it could be a few things...
#1. Maybe the head gasket is going and the fluid is leaking slightly into the exhaust jacket and burning off.
#2. Maybe I have a high pressure leak in one of the hoses that only acts up when I am driving the car.
#3. Could it be a faulty radiator cap?

Do a leakdown test, and remove all doubt. Easiest way to find the problem.

This is how it all starts. No doubt the coolant is blowing past the head gasket and burning out the exhaust. Problem is, it's also washing your lube off the cylinder, probably #6. Shut it down till you can get the head gasket done.Read the facts at the link below:

http://www.suprasonic.org/public_html/sonictech/mk3/mk3_pmtn.html

Yep, did the leak down test today. BHG.
The mechanic at the gas station that did the leak down test quoted my $1700.00 to do the head gasket with no warranty.

Yikes! Do it yourself and spend less than half that!

That is what I intend on doing. I am taking Friday off from work to start ripping it apart. It is a NA car and my son doesn't beat on it so we are going to use a stock gasket with new head bolts. Hopefully we won't see any damage to the block or head. It really hasn't had a drastic BHG yet. It has had heat spikes and it did overflow out of the radiator overflow bottle a few times.