Ron_H

This thread is not about a leaking radiator, though that's how my problem began........or so I thought. I noticed what appeared to be water leaking a slight bit from the passenger side plastic side tank after I crawled under the car and removed the underpan. I reasoned that the side tanks were simply old and leaking and getting worse. It started as a once a month refill up to the seam in the expansion tank, and now it has degenerated into a once a day refill and getting worse by the hour. Today I found a puddle of water under the car after leaving it in the parking lot of the food store in San Francisco. I filled up the tank, and three spare gallon water jugs I had with me for drinking water and headed back down the Peninsula toward Sunnyvale (about 45 miles away during a hot, dry, sauna like day. I made it half way before stopping to refill the tank and noticed some water from under the car at rest. I resumed my trip and arrived back in Sunnyvale. I had left the cap off in the city and lost about half a gallon at the half way point when the red warning light and coolant light illuminated. After filling to the top (Bill Ball's recommendation) I replaced the cap but only one click so as not to over pressurize the radiator. In Sunnyvale, I added another half a gallon.

However, and here is the question: To this point, I had assumed the water had been dripping on my belly pan and running off to the side or rear of it, since I could never detect any spillage under the radiator unless the car was parked with the rear higher than the front. Under those conditions, I would park it hot, and return to find a puddle under the spoiler. Today, however, I left the car running while I refilled it. I then looked under the car to discover no water at all coming from the front, rear or side of the belly pan. It was dripping heavily from the center tunnel just behind the cats and I could hear it hiss as it hit them. What is that all about?? And after the engine has been turned off, the flow seems to cease, though a full gallon had drained in the parking lot in San Francisco. It seems to be coming from a place where there is no water lines at all. I reasoned that it might be coming from the transmission lines and following them down until it simply drips off of them, and originates from the cooler in the radiator. Does that make sense?
I plan to put the car on a lift after it is really hot and observe the path with the belly pan off. Maybe the radiator is not leaking at all.

Any thoughts?? Anyone experience this situation in the past?? Maybe the menehunes have been fooling with my car at night because I didn't leave any offering of food for them at night? Many thanks to the person who can identify this mysterious leak.

Landseer

First thing I might do is pull the airbox and inspect the various heater hoses.

Mrmerlin

this sounds like a Heater control valve and or short hose, replace these first dont keep driving the car till the coolant leak is fixed, its possible that ahose will burst or otherwise cause a massive drain all at one time and then you might have the heads warp

smudaaar

I' wouldn't drive the car...... your going to **** your heads up! they are going to warp or....much worse things could happen!

Ron_H

Yes, I have thought about the heater hose and checked it a couple of months ago. It was in good condition then but the minor leak was still draining the coolant system. Just today I thought about that hose again since that seems to be the only thing that makes sense and the only source of coolant liquid that could find its way down to the tunnel. I will take off the air box tomorrow and have another look. I know all too well about losing the heater hose and immediate drain of the coolant system; it happened on a remote road to Boise, ID once just outside Rome, Oregon. I looked in the rear view mirror to see clouds of steam and water flying out behind the car and the heat guage started rising. I shut off the engine immediately and parked alongside the highway until I could call a tow truck to take me 100 miles into Boise. Luckily nothing happened to the engine. That incident happened all of a sudden, but this is slowly getting worse. The heater valve assembly seems the likely source, and I have a spare one and a spare hose which I carry ever since my incident in Idaho.
Thanks for responding to everyone.

Lizard928

my vote is for the heater hose, or valve itself. I have seen the bodies seperate and leak slowly, getting worse over time as more and more glue gets washed away.

Mrmerlin

dont use used parts to fix the car please replace these parts with new freshies

Ron_H

The heater valve itself is an Audi steel part. I tossed the old plastic Porsche part long ago. I wouldn't think a steel part would be defective but am about to tear into this area this morning. I'll report my findings.

Fogey1

Does your AC work?
Is it coolant or water? If it was coolant you heard hissing, you'd have probably smelled it.
Any chance it's condensate from the AC evaporator drain?

Will

Mrmerlin

using an Audi part may be part of the problem

Ron_H

The reason for that part is it is all steel, and is almost identical in concept and size to the plastic part by Porsche. Porsche saves weight in some strange places. I think they assume their cars will always have a pit crew around to service them between races instead of driven for 200,000 miles on the highway by mere mortals. I have a spare Porsche plastic part; I might install it just for grins along with the new hoses and sit back to see what happens. At least, as you imply, I'll have the part Porsche spec'd in there.

Mrmerlin

you could also have a cracked coolant bottle.
If the bottle is damaged make sure to replace the cap as well

Ron_H

The coolant vs water issue is moot because I have been putting in tap water for the last couple of weeks since it simply flows out again. I know, I know......unforgivable sin. I expected to install a replacement radiator this weekend though and fill with coolant; that radiator leaked also and will be sent back.

I haven't ruled out the bottle, but it seems to hold water overnight. Of course with pressure and heat, it could be leaking. I think that's the next item to replace after the heater valve and hoses. Today I let the engine build up to normal operating temp with the cap on and tight to build up pressure. The only leak I could detect was the slight one at the side tank. Nothing from under the car. I will install a new valve and hoses anyway, and not operate the AC at all until that is accomplished. The AC DOES operate very well and responds immediately when I acutate the AC switch. I reason that the heater valve thus does function, but may be leaking. I will definintely check the bottle too this afternoon, since I have to drive to a client's house about ten miles away. giving me plenty of time to build up to sustained heat. That will be the last drive in this car until this issue is resolved and the hoses/valve are replaced.

Bill Ball

Hi Ron:

You say it's dripping all the way back by the cats. That's where the heater/evaporator box drain is. Normally that is for condensation produced on the AC evaporator coils. If you were not running your AC, then it's something else....

That box holds the heater core too. If the heater core has a leak, then it would come out that drain above the cats. If your engine cooling system still has any antiftreeze left in it, then any of this drip that reaches the ground will be colored and smell/taste like antifreeze. This could happen even with the heater control valve closed, as these valves are notorious for leaking a little anyway. Also, I would expect you to detect the telltale odor inside the passenger compartment too.

I hope you don't have a heater core leak, as you know what replacing that entails. At this point, only the location of the drip points to that. I would expect more signs such as sweet smelling steam inside the passenger compartment, so I'm banking on being wrong and hoping it's just a heater hose or hose clamp up in the windshield cowl.

I have some time late next week (Thursday or Friday) and would be glad to come down and look at this with you. Let me know.

Ron_H

Bill, I have never noticed any sweet odors in the passenger compartment, but I think I will fill the bottle with antifreeze to explore your theory. However, It would answer some questions and narrow the alternatives. I also need to replace or repair that radiator.