Mrmerlin

check all of the clamps on the heater hoses at the rear of the engine bay and also the ones that connect to the heater core under the black cowl cover

Ron_H

I printed it out and have it handy. After I've received the side tank replacements I'll jump into that job. My passenger side tank has a relatively minor leak but needs immediate attention.

And I'll also be inspecting all of those clamps today or tomorrow. Unfortunately, I have to work for a living today. But it is cooler and our heat wave seems to have passed for now.

SharkSkin

Ron, two things worth noting that may affect how you interpret the symptoms.

1. With the AC on, the heat load on the engine cooling system is higher because the AC takes heat from the cabin and dumps it out right in front of the radiator. The difference could be enough to account for running OK without AC vs boiling over with AC.

2. I'm not an expert on the later climate control system, but doesn't it choose between running AC and metering hot coolant to the heater core to achieve a setpoint? If that's the case is it possible that you have a leak downstream of the valve that is only apparent when the system calls for heat?

Ron_H

Yes, on point 2. I have just returned from a trip to Santa Clara (Lafayette St.) and then to my garage in San Jose. When I returned to Sunnyvale, without running the AC at all, zero water is missing from the bottle, no water was seen under the car near the cats, and only a damp trickle from the side tank on the passenger side was evident with the car idling and at full temp (not even close to the first white line above the bottom), and no water was detectable from the hose where it goes into the heater box under the black plastic cover which I removed to monitor that hose. I stomped my feet, I scratched my head, I cussed and spit. I still can't figure this out, and said to myself to repeat the trip with the AC on and watch it spill out just above the cats. I didn't do that because that may prove disastrous. Hey, I never had a car with AC anyway, and thought it was just one more thing to go wrong; if I wanted to cool off, I opened a window. Who needs it anyway? Dead weight. I'll just drive nude.

Here's the puzzling aspect: Today I turned on the heater to full hot and watched the heater valve hose and the one to the heater core under the cowl cover. It certainly got hot because I touched it before the heat was on and then after to monitor the flow. NO leaks during a brief period while the car was parked by my office and the engine idling. I could have let it run a bit longer than five minutes, but I honestly think you have the clue: it happens when the AC is on. Otherwise whatever leak there is doesn't occur upstream of the AC/heater core.

By the way, Ador tried my caliper bolt but concluded that I might have to scrap the caliper to get it off because drilling it out seems the only solution and that will ruin the caliper. I have another idea: weld a nut on top of the caliper retaining bolt and then put a socket on it. Now all I need is a welder.

Ron_H

Update:
I drove the care about 25 to 30 miles yesterday afternoon (approximately 85 F and very dry). I didn't use the AC. I didn't use the climate control at all and kept the button all the way to the right, so theoretically, the heater core saw no coolant circulation. Upon returning to Sunnyale, NO coolant was missing from the reservoir, NO water was running out of the side tank, NO coolant was dripping from the area of the cats. Of course I was a bit warm and kept the windows down even on the freeway, but the leak wasn't happening.

Tomorrow I shall replace the hoses to and from the heater core and verify the connections, though they seem to be dry now.

Dave's theory seems to be true so far. After the hoses are replaced and I acutate the AC, I'll know if the problem is likely in the heater core area.

Bill Ball

So, running the heater does not produce a leak, but running the AC causes a pool under the cats. Dave's theory is certainly feasible, although surprising, as I would think heater alone would still leak. Anyway, after you see the pool form, back the car away and check whether the pool has antifreeze in it or is just evaporator condensate.

Ron_H

I didn't run the heater alone long enough to cause a significant leak; just long enough to fee the hoses into and out of the heater core housing become warm enough to cause a leak to develop. When I detected none, I shut it off. I need to add antifreeze to the coolant because I have long since exhausted the antifreeze in the system. It was leaking so badly it made no sense to keep adding expensive antifreeze. I'll put some in tomorrow after I've changed the hoses to/from the heater valve.

Nicole

Ron: If it turns out your heater core is bad, I have one in my garage that you can have.

Ron_H

Thank you Nicole. Maybe we can have a "dash removal" party. I will need to R&R the dash, pod and console and refinish it also while I'm in there. It will have to be after the Monterey Historics though, as I will be quite busy until then and will be staying in the Niles district of Fremont for awhile during August, so we'll be neighbors. In fact, why not organize a 928 group to storm the Historics on Sunday; Porsche is the featured marque and we should display a strong showing of 928ers, don't you think?

SharkSkin

Sounds like it only leaks when the system tries to build pressure. I would think that if the core was leaking you would have smelled hot antifreeze in the air coming from the HVAC -- maybe not now, but certainly when there was still antifreeze in the system.

Ron, do yourself and the environment a favor -- put antifreeze in only after you have solved the problem. Having said that though, you might want to put some water wetter or other additive in to lube the WP seal while you get it sorted out.

dr bob

Bill-

My casual nickel is bet on the heater valve or the hoses or the reservoir itself. A pressure test in the iveway will identify the leak quickly. I need a couple 5/16" hose fittings and a pressure gauge to go on a little instrument-sized pressure regulator I have surplus in the shop. Slowly increase system pressure with it to find the pee stream aimed across the firewall. Or borrow/rent one from Advanced. It will let you know exactly where the leak is.

Herman K

Turned out to be the pressure switch (928-641-513-00 - Pet Illustration 105-05 # 8) center seam and a pin hole in the "Y" pipe Pet Illusrtation 105-05 # 52) The water would travel along the litlle hoses of the pressure switch like a wick and drip some where else.

Ron_H

Thank you Herman. I will check this out. It seems it would be a blessing if I don't have to remove the console and dash.

Mrmerlin

Ron for the dash leak its simple if you dont smell coolant with the heat or AC system on then the coolant is leaking from the engine compartment.
If OTOH you do smell coolant then the the chances are good that you have a leak inside the car

Ron_H

I've never smelled coolant in the passenger compartment, even when I actually used antifreeze. I will put som anti freeze in tomorrow and that should help pinpoint the leak.