Q: Random and seemingly instantaneous coolant leak after attempting to bleed the cooling system.

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I was given this vehicle because the previous owner did not want to pay to have it fixed. The car would run for about 20 minutes before overheating. I would prolong overheating by running the heater. I decided to troubleshoot the issue and decided that bleeding the system was a good idea and easiest to do. After this I planned on replacing the radiator cap with the same pressure rating because coolant escaped through the cap. After my obviously failed attempt at bleeding the system I drove the car and it began overheating much faster than it normally did. I parked and shut off the engine before it could actually overheat and after 10-15 minutes of waiting for the engine to cool off, I saw a large coolant leak. Also, the heater trick stopped working. What did I do to have caused such a seemingly random leak? The leak seemed to originate from the right side of the engine so it might be the water pump or it could have leaked out of the cap again. Any advice or tricks? Thanks.

My car has 150000 miles.
My car has an automatic transmission.

It would seem that there may be excessive pressure in the system for some reason. Because you replaced the cap and now presumably this is keeping a better seal on the coolant from coming out of the cap, it may be possible that this has forced a leak elsewhere in the system.

The other question would be what is it that is causing the excessive pressure? I would recommend checking the thermostat to be sure coolant is flowing properly. Also check to be sure the coolant fans are coming on as they should and that the relays do not need to be replaced.

If you need assistance with getting this fixed, consider YourMechanic, as one of our mobile technicians can come to your home and diagnose your overheating issue firsthand for an accurate repair.

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