boost solenoid testing

[yawn]

Hi guys - just a quick question regarding our boost solenoid - it is supposed to hold vacuum on the inlet side (where the hose from the solenoid runs to the canisters). Just wondering what would be an acceptable bleed off time for the vacuum? 1 of mine is at 26 in mercury, the other is at 25. This is with the car on idling and vacuum gauge attached. When I turn the car off vacuum is still there but if you stand there and watch it, it starts to lose vacuum very slowly. Does that mean they have gone bad?

[vtl]

Are you running a tee off the inlet (its labelled as vac)?. I have brand new genuine BMW solenoids and they slowly bleed off vacuum when sucked on with a syringe (maybe a few mls over 15-20 seconds).

The solenoid mechanism only opens the valve, it relies on vacuum to such it back shut and can sometimes leak slightly under test.

If its slow then don't worry about it, the valves are not perfect seals. This doesn't mean they're not faulty though, I think they may still stuff up at higher temps. I have had an overboost at the racetrack and I think it was the solenoids leaking vacuum (closing the wastegates). Sounds similar to your issue in your other thread. I haven't reproduced the issue and will just install my set of solenoids as preventative maintenance.

[martymil]

When you test the solenoids did you disconnect the pipe that joins them together, as they share vacuum.

What you have to do is disconnect the vacuum balancing pipe and test the vacuum on each solenoid separately but make sure you have the other solenoid blocked off so it doesn't suck air while testing the other solenoid.

[yawn]

Originally Posted by vtl

Are you running a tee off the inlet (its labelled as vac)?. I have brand new genuine BMW solenoids and they slowly bleed off vacuum when sucked on with a syringe (maybe a few mls over 15-20 seconds).

The solenoid mechanism only opens the valve, it relies on vacuum to such it back shut and can sometimes leak slightly under test.

If its slow then don't worry about it, the valves are not perfect seals. This doesn't mean they're not faulty though, I think they may still stuff up at higher temps. I have had an overboost at the racetrack and I think it was the solenoids leaking vacuum (closing the wastegates). Sounds similar to your issue in your other thread. I haven't reproduced the issue and will just install my set of solenoids as preventative maintenance.

Yeah, mine were leaking a few mls over 15-20 secs too. Good idea to have it replaced I guess. Where did you come across info on heat causing the solenoids to malfunction? I have only read of heat causing the sticking wastegates.

[yawn]

Originally Posted by martymil

When you test the solenoids did you disconnect the pipe that joins them together, as they share vacuum.

What you have to do is disconnect the vacuum balancing pipe and test the vacuum on each solenoid separately but make sure you have the other solenoid blocked off so it doesn't suck air while testing the other solenoid.

Each solenoid is connected to it's own canister right? So for each solenoid, I tested by teeing in a vacuum gauge between a canister and the hose leading to its solenoid. I then started the car and let it idle for a minute or two just to get the vacuum pump going and checked the gauge to ensure I was getting a reading of 25/26 in Hg. Once it was raised to this reading, I turned off the ignition and checked the gauge to see whether vacuum was still holding - I figured if the vacuum pump is off, and the solenoid is good, then vacuum will be maintained. But yeah, you have a point - I will test again and this time clamp the hose that connects the 2 solenoids.

[vtl]

Originally Posted by sharkatron

Yeah, mine were leaking a few mls over 15-20 secs too. Good idea to have it replaced I guess. Where did you come across info on heat causing the solenoids to malfunction? I have only read of heat causing the sticking wastegates.

Its just a hunch of mine, no real evidence. If the valve is leaky it will allow vacuum to flow and be able to close both wastegates. The boost solenoids run in parallel so just 1 faulty solenoid stuck open can cause both turbos to overboost.

I have bench tested these things with a power supply and found that a brand new one can be made to leak after solenoid activation (just put 12V across the terminals) if you don't have a strong enough vacuum source to snap the valve back shut.

I have heard about sticking wastegates due to heat but I haven't seen evidence to support that either.

My car drives fine otherwise and I am not 100% sure if mine was even a wastegate control issue since I actually had the wrong firmware loaded on my Procede when I was at Winton raceway.

[martymil]

Originally Posted by sharkatron

Each solenoid is connected to it's own canister right? So for each solenoid, I tested by teeing in a vacuum gauge between a canister and the hose leading to its solenoid. I then started the car and let it idle for a minute or two just to get the vacuum pump going and checked the gauge to ensure I was getting a reading of 25/26 in Hg. Once it was raised to this reading, I turned off the ignition and checked the gauge to see whether vacuum was still holding - I figured if the vacuum pump is off, and the solenoid is good, then vacuum will be maintained. But yeah, you have a point - I will test again and this time clamp the hose that connects the 2 solenoids.

The only real way to test these and get a true reading is where the balancing pipe is, teeing in at the canister wont tell you what the solenoid is doing.

You have to disconnect the balancing pipe completely and test at that outlet with the car running, mine where 16 and 18, with the balancing pipe in place I was reading 20 to 21. After new solenoids where installed I got 26 across from both from memory.

So take the reading at the point where the balance pipe is not at the canister

[yawn]

Originally Posted by martymil

The only real way to test these and get a true reading is where the balancing pipe is, teeing in at the canister wont tell you what the solenoid is doing.

You have to disconnect the balancing pipe completely and test at that outlet with the car running, mine where 16 and 18, with the balancing pipe in place I was reading 20 to 21. After new solenoids where installed I got 26 across from both from memory.

So take the reading at the point where the balance pipe is not at the canister

So if I read this correctly, I should be testing the vacuum between the solenoid and the wastegate, with the the balancing pipe (the one that connects both solenoids right?) removed/clamped?

[martymil]

Remove the balance pipe and test each outlet seperately.

When testing each outlet the other should be blocked with a block off