EGR Solenoid Valve

[Brock94]

I'm trying to figure out a problem on a friend's '03-- it has a whistling sound from under the hood while driving that I thought was from a vacuum leak. I disconnected the vacuum tree from the intake manifold and connected a vacuum pump to each of the lines that go off of it.

I was able to hold vacuum on all of them except for the one that goes to the EGR solenoid. I checked the line that goes to the solenoid and it is fine-- it seems the solenoid itself is not holding vacuum (this is with the engine off). The problem is, I don't know if it should be. Can someone tell me if this is normal or if it means the EGR solenoid valve needs to be replaced?

There are no codes by the way.

Thanks!

 

[Diff Whack Daddy]

The EGR contol solenoid will bleed the vacuum pressur off until the PCM tells it to apply the vacuum to the actual EGR valve. Kind of a dumb design, but that's how it works.

 

[Brock94]

The EGR contol solenoid will bleed the vacuum pressur off until the PCM tells it to apply the vacuum to the actual EGR valve. Kind of a dumb design, but that's how it works.

Wow, that is strange. You'd think it would mess up fuel control. I guess we don't have to replace it though.

Thanks for the info!

 

[kf6zvt]

The EGR solenoid will bleed off the vacuum, not enough to affect the air/fuel mix, but enough to avoid a complete vacuum inside the solenoid.

When you apply 12vdc and a ground to the two terminals, it will open and pass a vacuum to operate the EGR.

Lots of stuff under the hood is vacuum controlled. Check the brake booster, the cruise control, heater blend door. There is a 3/8" hose that connects a vacuum port on the intake manifold to a point just "behind" the Throttle Body. Another source of the "leaking vacuum" sound is a hollow plastic "box" on the intake tube between the air cleaner and the Throttle Body.

 

[Diff Whack Daddy]

Where is the connection for the heater blend door?

 

[kf6zvt]

When I traced the vacuum lines, there is one that goes through the firewall. This connects to a series of vacuum tubes that control most of the heating/cooling "doors" that direct air flow within the cabin. A tube comes off this mess and goes to a diaphram unit that controls the blending of hot and cold air.

I'm old enough to remember when this was accomplished with wire cables that would either get seized with rust or just break. Vacuum is "better" just a pain to fix when there is a problem.

 

[Brock94]

Where is the connection for the heater blend door?

I think the blend door is electric on these vehicles. Other HVAC controls are vacuum activated though.

BTW-- what is that "black box" attached to the intake? I was trying to figure that out.