Scan says large EVAP leak

Tiny
SCOTTMAR98
  • MEMBER
  • 2007 HYUNDAI SONATA
  • 141,000 MILES
And so, the mechanic did a smoke test, found there was a small tear in a hose under the hood and repaired it. After a week when turning on the engine, the check light stayed on, and a scan was the same large Evap leak. Another smoke test showed nothing. Mechanic removed solenoids and found nothing wrong. He says replacing them will be a 50/50 chance. He gave up, but reset the light. Upon starting the car again, the check light went on. And the gas cap is new. Any suggestions?
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Friday, July 31st, 2020 AT 7:32 AM

3 Replies

Tiny
KASEKENNY
  • EXPERT
Unfortunately many mechanics just don't understand how this system works. The smoke testing is just part of the diagnosis as that will check for external leaks. However, this system can still leak internally. Basically the large leak code is telling you that the system is not building pressure like it is supposed to do. I attached a lot of info on this system but it needs to see the proper pressure in the system with the purge valve closed. If it does not see the pressure build then it sets this code.

More then likely the purge valve is leaking or the Close valve is leaking. If both of these are closing and sealing then the only other exit point for the pressure is the gas cap. So if you already replaced that then that leaves the close valve or the purge valve solenoid. The way to test this is to remove the line from the purge solenoid and hook up a vacuum pump and pull the system into a vacuum. If it holds a vacuum then the leak is the purge valve. If not then you have a leak somewhere else in the system.

The fact that he did not find smoke coming out anywhere is why I think the purge valve is the issue because the smoke would go into the engine. Did he remove the oil fill cap when smoke testing it? If so, he should have seem the smoke coming out of the engine if he ran it long enough. Let me know if you have questions and we can go from there. Thanks
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Friday, July 31st, 2020 AT 5:09 PM
Tiny
SCOTTMAR98
  • MEMBER
Thanks for your reply! If it is the Purge Valve, is this situation potentially dangerous to drive with?
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Sunday, August 2nd, 2020 AT 4:14 AM
Tiny
KASEKENNY
  • EXPERT
If this is not causing any performance issues then it is not dangerous to the vehicle but should be addressed as this is what manages the emissions control system. If it starts causing the engine to run poorly then it could cause a stall but if you haven't noticed it then I would not worry about that.
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Sunday, August 2nd, 2020 AT 6:47 PM

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