Ron_H

Bill, looking at the workshop manual, I see that I must remove the entire dash to access the heater/ac unit. This is not such a bad thing, since I have been putting off refinishing my dash. It was resprayed when I installed it but never coated with a satin matte finish like I used on the rest of the re-dyed upholstery pieces. So the dash reflects lots of sun and puts reflections in the winshield which is maddening. I just keep putting off respraying the matte coating because I have to do it while the dash is in the car. This may force me to complete this nasty job with the dash out of the car which is ten times as simple.

However, I am praying, (well, OK, hoping) that the problem is not in the heater core.

nosnow

When looking at the heater vavle check the outlet on the top of the passenger head. On my 86.5 the pressed in outlet came loose. It would hold due to pressure from the hoses ect but when there was pressure in the cooling system coolant would leak out, when the pressure equalized the lead would stop.

Bill Ball

Yes, taking the dash out is necessary to replace the heater core, but getting the box out involves some additional pain. Plus you would need to acquire a replacement core. Let's hope you find the leak elsewhere. Let me know if you'd like me to come over.

Bill Ball

I've seen this fitting come out on more than one car. JB Weld seems to work well for this repair.

Lizard928

if you wish to exclude that circuit, simply cap the two ports which normally run to the heater core. And then see if you still loose coolant.

Ron_H

Here's the latest on my situation. I just drove the car 25 miles in today's sauna like heat. Not a drop from the central tunnel/firewall, but I kept the AC off both ways. Yesterday up to San Francisco and back I had the AC on both directions and it was pouring out from around the cats. Seems like I may need a side tank repair at least, but that's not the major leak at this point. I hesitate to actuate the AC for fear of making things much worse. It sounds like the heater valve and hoses at least must be replaced and that stubby heater valve in my car appears to be swollen so it must be replaced regardless of any other fix. But Bill, you appear to be right on target, and I'll have to struggle along without AC until I can find time and cash to tear into the core. I estimate at least half a day for R&R dash and console plus painting dash with matte SEM paint. I haven't a clue how long to expect a core replacement to take.

Fogey1

Ron,

Your description above almost nails it down for AC evaporator condensate.

The evaporator and the heater core are separate items in the same box.

No reason to suffer without AC.

Bill Ball

Ron: Fogey is right. The heater core and AC evaporator are entirely separate units just housed in the same plastic box. Running the AC is not going to make the cooling system leak. I never meant to suggest that. I meant that either a perfectly functioning AC system OR a leaky heater core will drop water on the cats. If you weren't running the AC but saw water there, particularly water mixed with antifreeze, the the heater core is leaking. So, you have now shown you DON'T have a leaky heater core, as there was no dripping with the AC off. Your leak is elsewehere.

Enjoy the AC. I sure did today - vent temp in the high 30s while over 100F outside.

Ron_H

Then I shall immediately replace my heater valve and hoses. That's the only other place from which it must be coming. The amount of water that was dripping yesterday from above the cats was extremely high and expect evaporator condensate would be rather small, say a pint of so. This stuff was a gallon or two and dripping while the engine was still running. But why it didn't happen today is a mystery to me.

Bill Ball

Yes, the evaporator condensate would not be that much even if you lived in Houston (humid area). But turning the AC off should not affect the flow from the heater hoses or leaker heater valve.

I would pull the cover off the windshield cowl and look at the heater hoses where they clamp onto the heater core fittings. One of those hoses comes from the heater control valve and the other hose snakes down to a pipe under the coolant reservoir. Start the car and see if you find a leak in the cowl area.

Ron_H

Thanks Bill. I'll get this done tomorrow. I suspect the J shaped hose from the heater valve, but the stubby is also swollen as if ready to fail. I'll change them all.

Ron_H

Will:

I thought this was true since it was seeming to happen only when the AC was on and today it didn't happen while the AC was off. But the humidity around here today and yesterday was so low I don't know if there was anything to condense. It has been literally like a sauna around here. And the volume of water dripping under the cats was relatively enormous......yesterday.....but nothing today. I'll run it with the AC on tomorrow to determine if the dripping returns. Thanks for the suggestion.

Mrmerlin

Ron it would be a good idea to replace the HCV and short hose also the coolant bottle if its tan or brown and its cap B4 you continue driving.
This test drive thing is eventually going to cause a catastrophic failure that can result in having the car towed home or damage to the engine or both.
It would be better to borrow another car for the time being while the correct parts are procured.
Also consider replacing the coolant tank on the radiator, most of the rad shops can replace the side tanks as they have the correct tools, a new tank and seal is all thats needed to return the original radiator to operating condition.
Either way dont keep driving the car till it is fixed, your car is telling you something and you dont seem to be listening.........

Ron_H

I have another car to use. I'll register it and use it. I haven't been making test drives. I use my 928 as my driver and work car, and had not been using the Rabbit, but I agree that all of a sudden something will fail and I'll lose all the coolant and the heads. What I don't know is what part is responsible for all of this.

If I run the AC and drive in 100 degree weather the leak from around the firewall / tunnel / cats occurs and LOTS of water is lost as the car is running and just after it is shut down. The water bottle is then empty and must be refilled, although the cap was only on to the first click and not tightened; that means full pressure never developed. Then the system was refilled and the car driven WITHOUT the cap and it drained faster. The cap was replaced again after refilling and the car driven with the AC on and the leak at the cats was as bad.

The next day the car was driven without the AC on in 100 degree weather (not humid) and no leak occurred at the cats.

It seems the cap and bottle can't be at fault because coolant disappeared when there was no cap in place and thus no pressure built up in the bottle. I do agree however that the bottle should be replaced as prevention of future failure, along with the cap, which still seals well, though I'm not sealing it currently.

So, as Bill points out, the leak must be coming from the HCV or hoses or hose connections into the heater core, particularly since they are so close to the cats and behind the belly pan. I just don't understand why it happens so harshly when the AC is on and not when it is off? Some coolant is being lost at the side tanks, but not much. The catastrophe seems to be waiting to happen during a time if AC use, but coolant is excluded from the heater core during those times. And the amount of coolant leaking is far greater than what would condense.

JHowell37

My money is on one of the heater hoses. I just had to replace one the other day. Even with a functional heater valve, those hoses do get pressurized when the engine is hot, and coolant can spray out pretty rapidly when they leak, and depending on the direction the water is being sprayed, it can look like it's running down on the cats.

I did a write-up on radiator tank replacement, that received the Bill Ball stamp of approval if you're interested.