FYI An insidious potential power robbing vacuum leak you may have and are unaware of.
11-13-2015, 06:59 PM
#61
Three Wheelin'
So, I know I've got a vac leak in my TT, but my symptoms are different. I can hear the leak inside the cabin, and when I step on the gas it gets louder as well as cuts off the air vent. I think it's the valve behind the radio, but I would appreciate any input. Thx!
11-13-2015, 11:09 PM
#62
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
I suspect something else is at work because I am suspect you can hear a vacuum leak from the heater flap. Make a stethoscope out of an old hose and see if you can localize the source of the sound
Last edited by pp000830; 03-16-2016 at 11:19 AM.
11-14-2015, 08:59 AM
#63
Race Car
Originally Posted by pp000830
Just replaced three of the four vacuum actuators on the engine. The one under the Varioram intake manifold was removed by removing the rubber duct above the fan. Had to make a Phillips wrench by sliding a short screwdriver bit into the end of a ignition closed end box wrench a 12 point works better to orient the screwdriver bit. Takes about 30 wrench cycles to get each screw out. Used tape and a sliver of sheet metal to keep the bit in place. Hemostat very useful to remove and reinstall the screws, used rags to catch any dropped bits or screws. Very tedious but can be done removing just the actuator.Andy
PS, the replacement ones seem to have silicone diaghframs. Look to be more robust.
PS, the replacement ones seem to have silicone diaghframs. Look to be more robust.
11-14-2015, 09:15 AM
#64
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
11-14-2015, 08:13 PM
#65
Rennlist Member
Bad solenoid
Wasn't hearing the vram kick in at higher rpms, and top end seemed a little light on power, so I tested the system with my son as helper.
The top left & right vacuum diaphragm actuators worked properly when ignition was switched on, but thE bottom center actuator did not engage even at rpms up to 6500. Diaphragm worked fine when directly connected to vacuum, so that wasn't the problem, and also confirmed vacuum was good and there were no leaks.
Tested the control solenoid for that diaphragm with a 12v source and it didn't engage. Replaced it with the solenoid off the fresh air flap and it worked fine. Road tested and noted the vram sound came on at about 5000 rpm (though a bit hard to hear this with the LPMM mod), and top end seemed to pull much better.
Interestingly, the bad solenoid measured ok at 32 ohms so while the coil may still be good there is some kind of mechanical failure inside it. The other ones click audibly when power is engaged, this one makes no sound and the valve doesn't open. The good news is, the solenoid is much cheaper than the vacuum diaphragm actuators...
The top left & right vacuum diaphragm actuators worked properly when ignition was switched on, but thE bottom center actuator did not engage even at rpms up to 6500. Diaphragm worked fine when directly connected to vacuum, so that wasn't the problem, and also confirmed vacuum was good and there were no leaks.
Tested the control solenoid for that diaphragm with a 12v source and it didn't engage. Replaced it with the solenoid off the fresh air flap and it worked fine. Road tested and noted the vram sound came on at about 5000 rpm (though a bit hard to hear this with the LPMM mod), and top end seemed to pull much better.
Interestingly, the bad solenoid measured ok at 32 ohms so while the coil may still be good there is some kind of mechanical failure inside it. The other ones click audibly when power is engaged, this one makes no sound and the valve doesn't open. The good news is, the solenoid is much cheaper than the vacuum diaphragm actuators...
11-15-2015, 10:22 AM
#66
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
Can this improve the cooling of the engine?
.... withdrawn
11-15-2015, 02:18 PM
#67
Rennlist Member
Sounds like a real issue in your case. The intake noise might be "subtle" to some, but it is there (2x) and if you're paying attention should hear it. Does your fresh air/recirc button on the CCU cause a *thunk* from within the dash? If not, maybe its not actuating (thus vacuum leak).
To help determine if your actuators are good/bad, you can test the actuators by pulling off the tube to it and blowing/sucking on the tube to see the actuator move (or hear the leak). I used an old CamelBak hose to move my actuator for the fresh air/recirc to test it was working and to help line up the pivot bolt I had to replace.
To help determine if your actuators are good/bad, you can test the actuators by pulling off the tube to it and blowing/sucking on the tube to see the actuator move (or hear the leak). I used an old CamelBak hose to move my actuator for the fresh air/recirc to test it was working and to help line up the pivot bolt I had to replace.
Where am I supposed to apply vacuum "all in one go" to test actuators 2, 3a, and 3b? Am I supposed to apply it at check valve 8? Or am I supposed to apply it at the "top" port on "manifold #4"? Where is "manifold #4"?
Many thanks.
11-16-2015, 02:01 AM
#69
Rennlist Member
All 3 actuators should activate, provided you have vacuum. If the car has been sitting awhile you may have to run it for about 20 seconds at 2500 rpm to build vacuum first, then shut it down, and turn ignition back on. The actuators are controlled by the 2 solenoids (units labelled #1 in the diagram) which are essentially air valves: when they are energized by the ECU, they allow vacuum to reach the actuators so they do their thing.
You could also manually energize the solenoids with 12v power but you would have to remove the blower assembly to get at them. Or you could bypass the solenoids and hook up the actuators directly to vaccum, to see if they work, but again that means messing around with the vacuum plumbing. A real pain if you want to test them "all in one go". Why bother with all that, when the ECU does the same thing automatically when the ignition is turned on?
By the way, the actuator in the middle is hard to see because the air duct behind the cooling fan is somewhat in the way. I was able to just bend my air duct out of the way because it was recently replaced and it still flexible. The duct loses flexibility as it ages, so if yours is original or older you may not want to try this as the duct could break or crack. Instead you might want to use a borescope or mirror on a telescoping wand in order to view the actuator arm moving behind the duct.
BTW manifold #4 is lurking around underneath and at the left side of the vram unit. It's a black rubber piece that looks pretty much like #4 in the diagram.
11-16-2015, 10:22 AM
#70
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
Testing the heater flap vacuum actuator behind the CCU
Removed the CCU, didn't detach it from its electrical harness, found the pin on the end of the actuator arm missing. Reattached it to the vent louver mechanism with a tyewrap tested it for leaks with a length of vacuum hose attached to the actuator and drew on it with my mouth. Held vacuum. Then I reattached it to its vacuum hose source, started the car and actuated it via the CCU observing it through the CCU dash hole. Then slid the CCU back in.
Andy
Andy
11-16-2015, 11:14 AM
#71
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
The best way to check the 3 varioram actuators (2, 3a & 3b) is by simply having a helper turn on the ignition (without bumping the starter motor), while you watch the actuator arms in the engine bay.
All 3 actuators should activate, provided you have vacuum. If the car has been sitting awhile you may have to run it for about 20 seconds at 2500 rpm to build vacuum first, .
All 3 actuators should activate, provided you have vacuum. If the car has been sitting awhile you may have to run it for about 20 seconds at 2500 rpm to build vacuum first, .
Andy
11-16-2015, 09:20 PM
#73
Rennlist Member
Correct, the vacuum reservoir. It's hidden under the left rear wheel arch liner, looks kinda like a plastic egg box.
Mine has enough reservoir to run the vacuum actuators even after car hasn't been started for a couple of days. No leaks, I guess.
Mine has enough reservoir to run the vacuum actuators even after car hasn't been started for a couple of days. No leaks, I guess.
11-21-2015, 07:33 PM
#75
yes, but the problem isn't as obvois or severe
The non vram 993 and 964 use less vacuum as there are 2 fewer vacuum actuators. Missing are the top 2 which operate the L/R vram banks, else wise the systems are the same Except that the vacuum reservoir is smaller and hidden under the air cleaner box.
The non vram 993 and 964 use less vacuum as there are 2 fewer vacuum actuators. Missing are the top 2 which operate the L/R vram banks, else wise the systems are the same Except that the vacuum reservoir is smaller and hidden under the air cleaner box.