1994 Audi 100 just sent all of the water out of the cooling system
04-11-2017, 12:37 PM
#1
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1994 Audi 100 just sent all of the water out of the cooling system
Last week the heater core sprung a leak as my son pulled into the drive way. I bypassed it and it ran fine, but was leaking water out of the temp sensor at the bottom of the overflow tank. I just put in a new tank and filled the system. a little water was coming out from an unknown source. I tightened the hose and it seemed to stop the water. the tank was still full, the car was running for about 25 mins in the drive way. The temp gauge was about 1/3 from cold (normal). It was indicating a temp warning on the dash, but temp was still normal. I decided to give the car a drive to make sure it all works properly and possibly cool out that flashing temp. as I got going, the temp rose a little. 4 mins in, it blew all of the water out of it. I restarted it and ran it about 30 seconds further to get it off of the hwy and get in a position to coast it home. Where did the water go? the tank was full and appeared to be holding pressure fine. the temp gauge was normal when I restarted it for those 30 secs. it never got hot hot (just past half way). when I opened the hood there was steem from everywhere, but it just sent all of the water out.
04-11-2017, 12:41 PM
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just to add, upper hose got warm, then the lower hose got warm. I heard it pushing some air out of the hoses while it was running (thunking noise). I don't think that the fans kicked on, but I wasn't babysitting it, I just checked it periodically to make sure it wasn't getting hot.
04-11-2017, 05:26 PM
#3
Sounds like there was air in the cooling system..which will cause weird overheating and thuncking noises as the air/coolant boils easily and will not circulate well.
As you have the heater core by-passed..you need to bleed the air from the by-pass hose..which can be fiddly..loosen a hose clamp and get the air out of the engine block..Audi 2.8 12v engines are tough to bleed sometimes...it mat take a couple of attempts.
See the link:quattroworld.com Forums: Bleeding the cooling system
As you have the heater core by-passed..you need to bleed the air from the by-pass hose..which can be fiddly..loosen a hose clamp and get the air out of the engine block..Audi 2.8 12v engines are tough to bleed sometimes...it mat take a couple of attempts.
See the link:quattroworld.com Forums: Bleeding the cooling system
04-12-2017, 03:55 AM
#5
After a while the thermostat finally opens and dumps coolant into the block..which is very hot due to air..and the coolant immediately boils..and you hear "thunks" as the boiling coolant expands..and the steam (which expands with terrific force) blows out of the block
04-12-2017, 04:23 AM
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Thank you. I'll work on it and hope is comes back around. Could the cap on the overflow be at the end of it's life? I believe that that is where all of the water is escaping from.
04-12-2017, 05:59 AM
#7
Could be a bad cap..however if the coolant was boiling due to air in the block..the cooling system will pressurize above the rating of the cap and leak coolant.
Caps are cheap enough if there is any doubt
Caps are cheap enough if there is any doubt
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04-12-2017, 07:09 AM
#8
From the headline, I expected your story to sound like my old 70s Volvo... the line from the block to the firewall burst while accelerating up an on-ramp and I had a rooster-tail of coolant and steam filling my rear-view mirror view. Now, that's what I call sending all the water out of the coolant system!
I immediately let off the gas and coasted down an off-ramp, gingerly drove around a corner and parked at a gas station (maybe 1/4 mile extra distance from the venting location). The temp gauge rose steadily the whole time and just approached the over-temp warning area when I shut it down. As I recall, when we drained the system to repair it, there couldn't have been more than about 10-20% of the spec amount remaining.
I'd got the car with service history from the previous owner, and it listed standard services including a periodic replacement of the failed hose. But, its rotted condition told me that the mechanic had gotten lazy and checked it off without actually replacing it. That engine bay was pretty easy to get around in, except those hoses to the firewall were very hard to reach. Lots of scrambling around and improvising to get the corroded old hose clamps and rotted hose off those fittings...
I immediately let off the gas and coasted down an off-ramp, gingerly drove around a corner and parked at a gas station (maybe 1/4 mile extra distance from the venting location). The temp gauge rose steadily the whole time and just approached the over-temp warning area when I shut it down. As I recall, when we drained the system to repair it, there couldn't have been more than about 10-20% of the spec amount remaining.
I'd got the car with service history from the previous owner, and it listed standard services including a periodic replacement of the failed hose. But, its rotted condition told me that the mechanic had gotten lazy and checked it off without actually replacing it. That engine bay was pretty easy to get around in, except those hoses to the firewall were very hard to reach. Lots of scrambling around and improvising to get the corroded old hose clamps and rotted hose off those fittings...
04-12-2017, 08:02 AM
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The composite water line that is part of the heater core, cracked. I took the hoses off from the back of the engine, and got a new piece of hose long enough to make a smooth arc and ran it from one port to the other on the back of the engine.