Rosesbabe

Looking for some help on where to start on this one.....

Returning to my work parkade after 30 min trip when I was using my A/C for the 1st time this year (don't know if this has anything to do with anything?) - saw my thermostat go thru the roof and the temp warning light go on as I entered the dark parkade. Got to my parking spot 3 flrs down and on turning off the engine saw huge steam cloud from my passenger rear end of the hood. Massive loss of coolant (see pics) - seems to be from around the fill point at the rear end of the engine compartment. Walked back up thru parkade to trace the leak time - seemed to start 2 block away. I had therefore been losing coolant for a good 5-6 mins in the time it took me to get to my stall.

Took a few photos in order to see under the car for an obvious leak or hose break. Nothing stands out as odd. My 1st reaction is to panic and think the sky is falling. I have 2 questions. Where to start on identifying the leak source? Does anyone think I may have caused major engine damage running it dry for this long? Reluctant to start it. Will head home now and come back maybe tomorrow with some distilled water to see if I can figure it out.

Thanks in anticipation

SeanR

Check the right rear of the engine.

There is a heater control valve that has 2 hoses (small) attached to it, I'm guessing one of them burst.

Leon Speed

Maybe it was just the overflow on the coolant tank. In that case there's no leak.

If you suspect a head gasket leak, check if the oil looks like a milkshake. Pull the plugs and see if there's any coolant in the cylinders.

If all checks out, fill the coolant tank and see if it leaks again. And fix the overheating problem!

Jim bailey - 928 International

There are NINE different hoses in the cooling system ALL are pressurized when was the last time those 23 plus year old hoses were changed ? The most common one to burst is the short hose from the rear of the passenger head to the heater valve , to view you must remove the aircleaner. There is no point in putting water in because it is just going to rush out. That little short hose is a stepped hose bigger on one end than the other you might find something at an auto parts store that you can cut out a section for a TEMPORARY patch. Consider replacing the other hoses as well. The front radiator hoses which are easy to see often get done the others tend to be forgotten.

Mrmerlin

if you replace the short hose on the right rear cylinder head also replace the heater control valve

Rosesbabe

Thanks for the quick response. I will take a look at the oil and check out the rear hoses. As I will investigate the repair away from home, can it all be accessed from above? Assuming it is a hose break for the moment (merely my wishful thinking) any concerns about what damage I might have done running it HOT and dry? Anything I can test for once I get some coolant to stay in there and before/after I start her up? In the interim, I will go thru her records to check exactly which hoses were replaced by the PO. Just assumed it was all of them. Appreciate the help.

SeanR

It can be replaced from above, if you had a major failure like that you'd have known it way before you got to the parking garage.

Pull the air box off and look directly down from there and you will see the heater control valve and the hose that broke (i suspect) is right there on the block side of it.

Replace it, fill the car up with fluids. Take the rad hoses off and fill the radiator from there............ From the temp stat ...........hell, I'll take a pic so you can see easier.

brb.

SeanR

Hope this helps

SeanR

Ok, i need more lights in the garage, I didn't know I had that much gunk down there........

Good luck with the repair.

When you refill it, make sure you turn your heater to full hot as you "burp" the system. Squeeze the front hoses ( pictured) so it helps get the air out of the system.

Once you have hot air, you know your t-stat is opening up and you should be good to go. Check the coolant level after that too, or you will get a warning light and that is worrisome while driving.

Rosesbabe

Decided to get my baby home to work on her - got her towed back yesterday - Tow driver managed to convince me on inspection, to start her up and drive out of the parkade because his truck was too tall to get in. Other than my main warning light on - sounded all OK. (phew!!) Took all of 1 min to get out and shut down. No obvious hose splits or leaks when I took the air box off, and yes, a run thru the POs' records suggests only the front hoses have ever been replaced. I do see a sticky however under the clamp on the short hose that could indicate it was not original equipment. Only sign of a leak is a dribble of green fluid that remains ontop of clutch housing directly under, so I think I am close. Heater valve has some evidence of old water from crustation on it. Looks like getting in and out to do the replacement is going to be a bitc... I mean "tricky" back there. Any tips?

nosnow

It is actually pretty easy to do the heater valve and the short hose. All you have to do is take the entire airbox off as mentioned above.

I suggest while you are in there to bite the bullet and do the heater hoses, the small hose from the Y-Pipe to the coolant bottle (this could have also been the culprit). Due to the complete utter bitch of the last hose I usually change the coolant tank as it is only an extra ~120 and ensures I won't have to go back for many years if at all. Of course in both my cars the tanks were solid orange and no longer clear due to age. Don't forget to inspect/replace the radiator cap.

morganabowen

The same thing happened to me yesterday, and I missed the San Diego run I'll take a look at it tomorrow. This thread helps me

Rosesbabe

I am playing detective here and would appreciate some feedback on my thought processes. I am having second thoughts on the idea that I may have blown a hose, since I haven’t found a split hose or one perished enough to have dumped that much coolant. I will take the advice and replace the old ones back there anyway, now I have the air box off, but I am now thinking that it may have been the overflow kicking in and I have an overheating problem.
I am wondering about the possibility of the system not having enough coolant to begin with. How do you know how much you have in there? Do you measure in the expansion tank? If you add coolant to the expansion tank, does it fill the system or can it just sit in there, blocked by an air plug? The PO replaced the original belt fan with an electric and did not install it adequately, resulting in some wobble and bearing wear on the fan. Job #1 for me was to replace it with another. If the PO cut the main upper hose to install the thermostat and did not fill the way SeanR suggested (thanks for the help by the by) could it be that I have been running all this time with too low a coolant level? Friday was the first warm day when I have had the car under load + A/C since I purchased last fall. If the system was being stressed for the first time and had inadequate coolant, would it have boiled, expanded and dumped to the overflow?? The dump would reduce the coolant level even further, leading to increased heat. It would explain why the coolant trail got bigger and bigger from where I first traced it on the road. Also, if there was air in the system, could the thermostat installed in the upper radiator hose be fooled if not submerged and not be triggered?

Cheers

Mrmerlin

coolant level should run at the seam in the tank.
To fill your system you only have to fill it from the coolant tank nothing special here as the system is a self bleeding system( note the small hoses to top of the water bridge and the top of the radiator,) fill the system and let it run with coolant cap off and the heater switcched to full hot, till the fans come on.
Once this stabilises install a new cap and drive the car for about 5 miles with heater on, this should purge any air out of the system and then let it cool down and then top up as necessary.
If your getting bubbles in the tank then chances are good that you have a blown head gasket or cracked head

Tails

It could be an air lock which may have been caused when you turned on your airconditioning.

The cabin heater is controlled by the vacuum operated heater controlled valve and if you have had no heat on for a while and you turn your A/C on this bring the heater valve into the circuit to control the outlet temperature into the cabin by mixing the cooled and heated air to achieve the cabin temperature you have set on the temperature slide.

When the car is parked the water level in the heater core drains partially out of the core and this is what my have caused the air lock.

Fill the system up with correct water/coolant mixture and bleed air from system and check operation of cooling systme.

Tails 1990 928 S4 Auto