terrapin24h
New Member
- Joined
- November 6, 2006
- Messages
- 5
- Reaction score
- 0
- City, State
- rochester, ny
- Year, Model & Trim Level
- 07 sport trac
All--
My first post ever! First i want to say thanks for a great forum. I've learned alot about the EX by just reading through all the posts. Now on to the meat of my post!
A week or so ago, our 2007 V6 threw a "gas cap loose" light or MIL. I had the code read at a parts store and got a P0456(evap-small leak). On goes a new gas cap. 3 days later still no love, but a new problem. I noticed that everytime i accelerated(Eng vac would go down) i would hear a hissing sound. After poking my head around, i discover the sound coming from the vacuum bottle under the pass side of the dash that "powers" the HVAC vac motors for vents and such. So i trace the lines around and dont see anything broke or disconnected. I trace the lines through the firewall and into the eng compartment, and happen across a crappy little check valve. Long story short, this valve ended up being the issue. While i was trying to track one down, I got a check engine light, that resulted in a P0455(large leak). About the same time, my AC would spontaneously switch from vents to defrost. Now i knew i was on to something. I could not find a check valve that was identical to the factory valve; the only ones i could find had a fat nipple and a skinny nipple, so i slid a piece of small vac tubing over the skinny nipple to make the vac line fit snugly. I then added hose clamps to each side to further ensure a snug fit. 4 days now and no light!
Hypothesis:
when the evap mgmt valve was open as part of a cycle test, AND engine vac dropped, the bottle would have the most vac, which would result in a "rush" of vapor/air to equalize the pressure. Then when the VMV would close it would see less press in the system than it thought it should resulting in the conclusion that there was a leak somewhere in the evap system. The resulting equalization would result in the vac motors for the vents "closing" causing the flaps to return to a home position. Then once the engine pumped the vapor out of the tank vac got re applied and the vents returned to thier proper state. Note that early on, I DID NOT hear or notice any other wierd behaviour. It was only after the problem had existed for a few days that I heard the hissing sound.
I put a vac pump on the old check valve, and it held until i got over 20in-hg. Then it would leak down to about 19 or so.
Pretty funny though, how the hvac controls could affect the evap control system.
Hope someone else gets some use out of this!
--chris
My first post ever! First i want to say thanks for a great forum. I've learned alot about the EX by just reading through all the posts. Now on to the meat of my post!
A week or so ago, our 2007 V6 threw a "gas cap loose" light or MIL. I had the code read at a parts store and got a P0456(evap-small leak). On goes a new gas cap. 3 days later still no love, but a new problem. I noticed that everytime i accelerated(Eng vac would go down) i would hear a hissing sound. After poking my head around, i discover the sound coming from the vacuum bottle under the pass side of the dash that "powers" the HVAC vac motors for vents and such. So i trace the lines around and dont see anything broke or disconnected. I trace the lines through the firewall and into the eng compartment, and happen across a crappy little check valve. Long story short, this valve ended up being the issue. While i was trying to track one down, I got a check engine light, that resulted in a P0455(large leak). About the same time, my AC would spontaneously switch from vents to defrost. Now i knew i was on to something. I could not find a check valve that was identical to the factory valve; the only ones i could find had a fat nipple and a skinny nipple, so i slid a piece of small vac tubing over the skinny nipple to make the vac line fit snugly. I then added hose clamps to each side to further ensure a snug fit. 4 days now and no light!
Hypothesis:
when the evap mgmt valve was open as part of a cycle test, AND engine vac dropped, the bottle would have the most vac, which would result in a "rush" of vapor/air to equalize the pressure. Then when the VMV would close it would see less press in the system than it thought it should resulting in the conclusion that there was a leak somewhere in the evap system. The resulting equalization would result in the vac motors for the vents "closing" causing the flaps to return to a home position. Then once the engine pumped the vapor out of the tank vac got re applied and the vents returned to thier proper state. Note that early on, I DID NOT hear or notice any other wierd behaviour. It was only after the problem had existed for a few days that I heard the hissing sound.
I put a vac pump on the old check valve, and it held until i got over 20in-hg. Then it would leak down to about 19 or so.
Pretty funny though, how the hvac controls could affect the evap control system.
Hope someone else gets some use out of this!
--chris
