Coolant Leak
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Rennlist Member
Joined: Feb 2009
Posts: 290
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From: Manotick, Ontario
Coolant Leak
Below is a post from the PCA Boxster Registry regarding a coolant purge cause by an air bubble in the cooling system. Same thing happened to me a few weeks ago at a 95F track day at Calabogie Motorsports Park.
Summary:
Evidently an air bubble in the cooling system can work its way to a restricted place and stop the flow of water causing the system to overheat, pressurize AND dump a large amount of coolant. Once the pressure builds up high enough the air bubble moves along.
I came off track from an easy session and the coolant system proceeded to dump a large amount of coolant. Turned out it was a tad over one gallon. Luckily it did it starting one car length from the end of the hot pits and I did not trash the track!
Details:
This past Monday - Tuesday was a track event at VIR on the north course for our region. We have not driven the north course before. The north course has a cut through starting right after the bridge which links back into the main track at turn 14. The rest of the course is T14 through T7 which we are all very familiar with.
Black was the very first run group of the day Monday. Right prior to the 8:30 black group we had parade laps, no helmets, slow speed just to show our students the line. So I drove 15 min of parade laps in my car with my green student, dropped him off, and then went out for my session. The ambient temp could not have been any more than high 70's. I had read tips on the cut through and was driving moderately trying to get the line down. Since I was going slowly during the unfamiliar portion of the track I just decided to take it easy on the familiar portion to have a similar rhythm. After about 5-6 laps it was not clicking so I decided to come in and read over the track tips again. A friend also came in early right behind me.
So I pull to a stop in the paddock and the event chair has followed me to my spot and asks "do you have an air bubble"? Puzzled I asked huh? To which he points out my spewing coolant. I look and there is a solid line of coolant on the paved portion of the paddock all the way as far as I can see and a growing puddle underneath my car! I bend down and it is pouring out in a stream like it is coming out of a garden hose.
We have an active thread here on operating temps and I had noted that my temp was a tiny bit higher after the low temp thermostat install, a tick over the 180 on the street and maybe about 190 on the track. I had been watching the temp and it was in the usual range, think I did note it was a bit higher as I was headed to my paddock spot but definitely not as high as the mark in between the 180 and 250 'numbered' marks. The red range on my gage is at the 250 mark - Maybe I was close to 200.
Man did the worry, stress, panic set in at this point. All kinds of thoughts running through my head from what is going on, how will I get home, my two -event is a bust etc. The event chair also has a Boxster and explained he had the same thing happen from an air bubble. He asked if I had had any maintenance done recently. I said I had the water pump and thermostat replaced proactively in may, then my son and I did double duty at Roebling road in June and I've been DD'g her with no issues. Odd to happen this long after the maintenance.
Several phone calls later and chats with the Tech lead who happens to have a garage too and all thought it was an air bubble. This is what the advice was and what I did.
Remove the oil and water caps then pull up the plastic cover. Underneath the plastic cover is the relief valve the upper part of this thread is speaking of.
1. Get distilled water. My Porsche coolant was at home in the garage. The answer was no to my question if there was any coolant available at the auto parts store which could be safely mixed with the Porsche coolant in the system. Distilled water was preferred to not have the minerals from a corrosion perspective. Bum a ride to town, food lion was a bust and found it at all places - CVS drug store and at a decent price. 1.58 per gallon. I grabbed all 4 they had not knowing how much I needed.
2. refill the overflow tank with the motor running to mix the cool and hot water. Did not know how much had come out but knew the overflow tank was empty. when empty there is a low level sensor which turns on a red light on the temp gage. It is on the gage itself, not an illuminated circle in the row of lights. So as I started the car a friend started pouring in water. She took exactly one gallon to refill - strange it was exactly one gallon!
3. open the pressure relief valve to release any trapped air. I figured if the tank was empty it was likely I now had more air in the system. When I first lifter the release wire I could hear air escape. (Note: each time I lifted it the rest of the weekend there was never again the sound of air coming out.) The release can be lifted and release pressure then go back down or lifted completely up and lock in the open position.
4. with the release lever in the open position (perfectly vertical ) drive at high rpms with the heater on full blast. Needed the heater on to circulate water through the whole system. So this part was happening at lunch time when it had gotten to about 90 degrees! So there I am driving in second gear between the north course paddock and the south course paddock (a 3.4 mile round trip) with the heater on 85 degrees and doing 3500 to 3800 RPMs with the valve open. After one lap I stopped and checked the water level and it took about 1.5 pints. Good news - looks like air is working its way out of the system. Off for lap two - this time maybe 2-3 ounces max. After lap three it was still full.
5. updated the tech head and he suggested now closing the valve and doing some highway speeds to see how she does. So off for about 10 miles on the road at cruising rpms. Temp actually lowered to right at 180. Returned and asked the tech lead ok, how do I determine if it is ok to track and not be jeopardizing my friends with a coolant drop. unfortunately no easy answer here.
It is about 3pm by now (been sandwiching all this in between taking my student out!) I decide to go out for 3-4 laps, watch the temps, come in early and check the level. Level was totally full.
I go out for the last black session of the day, run almost all of it and all is fine.
Tuesday I kept a close eye on her and ran all my sessions plus some others and no problems and did not have to add any water.
So I have learned our systems are extremely difficult to bleed all of the air out of them. Turns out my shop had the car on a vacuum for 45 minutes to try to empty it all out. Assuming this whole saga was caused by an air bubble I have learned it seems an air bubble can be in the system for a while before it manifests itself as a problem. (16 track sessions by my son and I, 750 miles to savannah, plus DD'g in between the maint and this event). Later on someone said if I had lifted the relief valve while it was spewing I might have been able to relieve the pressure and stop the spewing saving coolant. Did not know this at the time, do not know if this is safe to do without a scalding risk so be careful here! (Also, my plastic cover was in place and I could not have gotten to the relief as you need to remove both caps to do this)
hope this helps - knowing what to do if you happen to have an air pocket - it sure was stressful but in the end it turned out to be a good track weekend.
the only thing I can think of which may have triggered this was I noticed Monday morning when I went over to the gas pump at 6:15am that since it was a low in the high 60's that night and the car was set on auto mode on 74 that it seemed the heater was running. I wonder if it did open the valves to the heater sensing I wanted the car above ambient temps and this 'moved' the air bubble. who knows!
Also, if you are tracking the car take the plastic cover off that goes above the coolant relief valve and leave it off so you can release the pressure and halt the coolant purge if there is a next time. I simply stored that little pastic cover away, and take extra coolant and distilled water with you to the track - if it happen again you are prepared.
Summary:
Evidently an air bubble in the cooling system can work its way to a restricted place and stop the flow of water causing the system to overheat, pressurize AND dump a large amount of coolant. Once the pressure builds up high enough the air bubble moves along.
I came off track from an easy session and the coolant system proceeded to dump a large amount of coolant. Turned out it was a tad over one gallon. Luckily it did it starting one car length from the end of the hot pits and I did not trash the track!
Details:
This past Monday - Tuesday was a track event at VIR on the north course for our region. We have not driven the north course before. The north course has a cut through starting right after the bridge which links back into the main track at turn 14. The rest of the course is T14 through T7 which we are all very familiar with.
Black was the very first run group of the day Monday. Right prior to the 8:30 black group we had parade laps, no helmets, slow speed just to show our students the line. So I drove 15 min of parade laps in my car with my green student, dropped him off, and then went out for my session. The ambient temp could not have been any more than high 70's. I had read tips on the cut through and was driving moderately trying to get the line down. Since I was going slowly during the unfamiliar portion of the track I just decided to take it easy on the familiar portion to have a similar rhythm. After about 5-6 laps it was not clicking so I decided to come in and read over the track tips again. A friend also came in early right behind me.
So I pull to a stop in the paddock and the event chair has followed me to my spot and asks "do you have an air bubble"? Puzzled I asked huh? To which he points out my spewing coolant. I look and there is a solid line of coolant on the paved portion of the paddock all the way as far as I can see and a growing puddle underneath my car! I bend down and it is pouring out in a stream like it is coming out of a garden hose.
We have an active thread here on operating temps and I had noted that my temp was a tiny bit higher after the low temp thermostat install, a tick over the 180 on the street and maybe about 190 on the track. I had been watching the temp and it was in the usual range, think I did note it was a bit higher as I was headed to my paddock spot but definitely not as high as the mark in between the 180 and 250 'numbered' marks. The red range on my gage is at the 250 mark - Maybe I was close to 200.
Man did the worry, stress, panic set in at this point. All kinds of thoughts running through my head from what is going on, how will I get home, my two -event is a bust etc. The event chair also has a Boxster and explained he had the same thing happen from an air bubble. He asked if I had had any maintenance done recently. I said I had the water pump and thermostat replaced proactively in may, then my son and I did double duty at Roebling road in June and I've been DD'g her with no issues. Odd to happen this long after the maintenance.
Several phone calls later and chats with the Tech lead who happens to have a garage too and all thought it was an air bubble. This is what the advice was and what I did.
Remove the oil and water caps then pull up the plastic cover. Underneath the plastic cover is the relief valve the upper part of this thread is speaking of.
1. Get distilled water. My Porsche coolant was at home in the garage. The answer was no to my question if there was any coolant available at the auto parts store which could be safely mixed with the Porsche coolant in the system. Distilled water was preferred to not have the minerals from a corrosion perspective. Bum a ride to town, food lion was a bust and found it at all places - CVS drug store and at a decent price. 1.58 per gallon. I grabbed all 4 they had not knowing how much I needed.
2. refill the overflow tank with the motor running to mix the cool and hot water. Did not know how much had come out but knew the overflow tank was empty. when empty there is a low level sensor which turns on a red light on the temp gage. It is on the gage itself, not an illuminated circle in the row of lights. So as I started the car a friend started pouring in water. She took exactly one gallon to refill - strange it was exactly one gallon!
3. open the pressure relief valve to release any trapped air. I figured if the tank was empty it was likely I now had more air in the system. When I first lifter the release wire I could hear air escape. (Note: each time I lifted it the rest of the weekend there was never again the sound of air coming out.) The release can be lifted and release pressure then go back down or lifted completely up and lock in the open position.
4. with the release lever in the open position (perfectly vertical ) drive at high rpms with the heater on full blast. Needed the heater on to circulate water through the whole system. So this part was happening at lunch time when it had gotten to about 90 degrees! So there I am driving in second gear between the north course paddock and the south course paddock (a 3.4 mile round trip) with the heater on 85 degrees and doing 3500 to 3800 RPMs with the valve open. After one lap I stopped and checked the water level and it took about 1.5 pints. Good news - looks like air is working its way out of the system. Off for lap two - this time maybe 2-3 ounces max. After lap three it was still full.
5. updated the tech head and he suggested now closing the valve and doing some highway speeds to see how she does. So off for about 10 miles on the road at cruising rpms. Temp actually lowered to right at 180. Returned and asked the tech lead ok, how do I determine if it is ok to track and not be jeopardizing my friends with a coolant drop. unfortunately no easy answer here.
It is about 3pm by now (been sandwiching all this in between taking my student out!) I decide to go out for 3-4 laps, watch the temps, come in early and check the level. Level was totally full.
I go out for the last black session of the day, run almost all of it and all is fine.
Tuesday I kept a close eye on her and ran all my sessions plus some others and no problems and did not have to add any water.
So I have learned our systems are extremely difficult to bleed all of the air out of them. Turns out my shop had the car on a vacuum for 45 minutes to try to empty it all out. Assuming this whole saga was caused by an air bubble I have learned it seems an air bubble can be in the system for a while before it manifests itself as a problem. (16 track sessions by my son and I, 750 miles to savannah, plus DD'g in between the maint and this event). Later on someone said if I had lifted the relief valve while it was spewing I might have been able to relieve the pressure and stop the spewing saving coolant. Did not know this at the time, do not know if this is safe to do without a scalding risk so be careful here! (Also, my plastic cover was in place and I could not have gotten to the relief as you need to remove both caps to do this)
hope this helps - knowing what to do if you happen to have an air pocket - it sure was stressful but in the end it turned out to be a good track weekend.
the only thing I can think of which may have triggered this was I noticed Monday morning when I went over to the gas pump at 6:15am that since it was a low in the high 60's that night and the car was set on auto mode on 74 that it seemed the heater was running. I wonder if it did open the valves to the heater sensing I wanted the car above ambient temps and this 'moved' the air bubble. who knows!
Also, if you are tracking the car take the plastic cover off that goes above the coolant relief valve and leave it off so you can release the pressure and halt the coolant purge if there is a next time. I simply stored that little pastic cover away, and take extra coolant and distilled water with you to the track - if it happen again you are prepared.
Race Director
Joined: Sep 2006
Posts: 19,031
Likes: 266
From: Bentonville, AR
Not sure I can agree with that difficult to bleed all the air out of the system comment.
Several of my cars have had the coolant replaced over the years and not once has the process left any air pockets in the system.
The first time I was skeptical and drove the Boxster around Wichita KS in July heat for several hours to ensure the refill left no air pockets.
There were none.
Since then I just pick up the car and go.
(I was told that one step of a proper coolant refill is to pull enough of a vacuum the coolant hoses collapse.)
AFAIK, the heater core does not have a valve that controls the amount of coolant that flows through it. The amount of heat is controlled by an air flap that directs none, some or a lot of air.
There is no reason to release the pressure. In fact if the system is working right it maintain pressure. It is the pressure that is present when the coolant is very hot that keeps the coolant from boiling, flashing to steam.
If you release this pressure -- ignoring the scalding risk -- the hotter spots/areas of the engine can develop pockets of steam (air) that create what you seek to avoid.
Sincerely,
Macster.
Several of my cars have had the coolant replaced over the years and not once has the process left any air pockets in the system.
The first time I was skeptical and drove the Boxster around Wichita KS in July heat for several hours to ensure the refill left no air pockets.
There were none.
Since then I just pick up the car and go.
(I was told that one step of a proper coolant refill is to pull enough of a vacuum the coolant hoses collapse.)
AFAIK, the heater core does not have a valve that controls the amount of coolant that flows through it. The amount of heat is controlled by an air flap that directs none, some or a lot of air.
There is no reason to release the pressure. In fact if the system is working right it maintain pressure. It is the pressure that is present when the coolant is very hot that keeps the coolant from boiling, flashing to steam.
If you release this pressure -- ignoring the scalding risk -- the hotter spots/areas of the engine can develop pockets of steam (air) that create what you seek to avoid.
Sincerely,
Macster.
