skl2

So I have been a little skeptical lately that my Varioram is working because I dont get that noticeable change in audio from the rear under hard acceleration. I noticed this after driving a friends 993 back to back with mine. I spent this weekend fixing the TT hose, checking vacuum, disconnecting and checking the actuators (they seem to be working and holding vacuum fine) and after driving again it didnt change anything. So, I am kind of at a loss. Could I be pulling a vacuum but not enough to cause the actuators to open at the correct RPM? I didnt test with a vacuum gauge, but I did pull a hose after running the car and it obviously was under negative pressure. I also cycled the ignition and the actuators all moved.

Basically, Im at a loss...and I missing anything that could be causing the varioram to not work?

TIA.

bobt993

You have a couple of things to check.

Resonance flap also needs to be working which is located just behind the fan on the underside of the varioram. (cross chamber)

You need to make sure the check valves are working on the left side tree. If one is leaking you loose vacuum at high rpms when there is little or none being added from the engine and it is only using the canister. You also can check the vacuum reservoir in the fender well by taking the wheel off the driver side and check for leaks (not a typical problem). Also the connecting tree below the varioram sometimes collapses and does not let the proper level of vacuum through. (black plastic Y connects the two actuators).

Best way to tell is on a dyno. The actual power should start showing around 5500 rpms. The actuators will close along with the resonance flap. When a check valve goes bad you will see the valves close, but then fail to stay closed as the rpms increase to redline. Your rpm plot will go flat as the rpms increase and then start to loose power.

skl2

Thanks for your reply. Is there a good method for checking the check valves? Also, the tree you are referring to? Is that behind the blower motor? What shapes should I be looking for? Thanks again.

bobt993

Yes, behind the blower motor. There is a metal bracket that holds the various vacuum lines vertically. There are several going into a single connector that ends up on a check valve. A bit of work to remove with it in the car, but it can be done. Best option is to pull the varioram module off and work on the lines while it is on the bench. Taking it to a dyno would allow you observe the operation of the actuators without taking everything apart. The varioram does not function correctly by reving the engine you need a real load on the drive train to see the system work. There are several well documented threads on the maintenance of the vacuum lines on rennlist that you can do a search on if you just want to start replacing parts. (rather cheap parts and easy to replace). The check valves allow air to flow in one direction only. This is how vacuum is stored in the reservoir to keep the actuators working when there is little or no vacuum in the intake manifold. A good check valve will allow you to blow air in one direction, but not suck air back through it. Pretty simple stuff, but they do start leaking or go completely bad.

ToreB

There's a vacuum line running along the wiring harness to the dashboard to the HVAC resirculation flap actuator. This line could have a leak and be stealing vacuum. The rubber neck hose on the actuator could be disconnected. It's placed behind the climate control unit, and can be seen from underneath the dash.
I've also seen one case of damaged vacuum hose due to a wire short/fire in the cable harness somewhere along the route from the engine compartment to the dash.
See the Details page on my HVAC DIY pages:
www.porschehvac.bergvill.com
Cheers,
Tore

skl2

Bob, I know what you are referring to when you say the "tree". This past weekend I had the blower motor out and did the spring fix to the TT hose (to keep it from collapsing) that I believe connects to the check valve you are talking about.

To check the acuators, I pulled the vacuum lines to each one and hooked up a sringe to the vacuum line going to the acuators. I then applied suction to see if the the acuators would move, and hold. All 3 seemd to move and hold vacuum which tells me the diaphrams are ok and the acuators are functioning properly.

One thing you mentioned has me thinking: When I drive the car and apply full throttle, there is a very audible clicking (rattle like) noise that comes from the driver side rear wheel well area. I almost took the rear wheel off and fender liner out to see what the hell was back there that could be making such a noise. Now, Im curious if I have a faulty vacuum resevoir? Under full load, perhaps the resevoir is leaking and that is what I am hearing creaking/clicking in the wheel well? Has anyone noticed this before?

Tore, I will check the line you are referring to behind the CCU - I have had the CCU out 3 times in the last week to look for a rattle (which I found and fixed!) and didnt notice the rubber line. THanks.

guards red

Hi,

The initial check of the Varioram system is quite easy, you just need to turn the ignition key to the second point, before the starter kicks in, and you should get a loud "Clack!" from the back of the car as both the Varioram and resonance flap actuators cycle. They do that every time you switch the ignition on to the second position. If you still have doubt get someone to switch the ignition on (no engine start) whilst you observe the flaps, they should cycle with each ignition.

If nothing happens run the engine for a few minutes to ensure that there is enough vacuum in the tank to cycle the flaps. The tank holds enough to do 5-10 repeated checks. The tank is just a big plastic bottle, it can be fractured over time but is not more sophisticated than that.

If you still have nothing check the solenoids are connected to the wiring loom. The solenoids are on the intake runners on the left bank just underneath the plenum. The check valves are next to be looked at along with the tubing under the manifold.

See this thread for plumbing:

https://rennlist.com/forums/993-foru...ferrerid=21390

Regards
GR

skl2

Hey GR....I cycled the ignition once and all the flaps cycled correctly. However, I do not get more than one or two cycles before I have to start the car again to build up more vacuum. Could this point to another case that the reservoir is leaking??

guards red

Hi,

If that's the case you're not too far off a solution. Rather than the tank being at fault (though I'm not ruling this out) I would be looking at the check valves.

If the car is a C2 is has two of these, one for the brake servo the other for the Varioram. Both are on the "tree" at the back of the engine. The Varioram valve is the one connected to a tube with multiple take offs, this tube should be your first check as it collapses with age allowing the tank no vacuum. If this is fine I would disconnect all the take offs from this tube bar one which you connect to a vacuum gauge (cheap on eBay) and switch on the engine. It should build strong vacuum which should not diminish over hours let alone minutes. If it goes quickly you're looking at a new valve. The do fail! If this test is fine then you are looking at the plumbing downstream. Looks complicated but it's not. Reconnect each item in turn looking for the one that leaks. Another candidate is the one that Tore mentions, its a line that runs all the way forward to a point forward of the windscreen wipers. This is often disconnected when people fiddle with the pollen filters.

The vacuum tank is in the rear left wheel well. Take the wheel off, the wheel well liner and the tank is there just forward of the wheel. It's black and has a "bubble" effect finish. Looks like it has eggs in it!

Good luck, let me know how you get on.

JM993

It's possible you have a small vacuum leak somewhere. If you have a miti-vac pull a vacuum hose and draw vacuum from the system. If vacuum doesn't hold, you have a leak. The next step is process of elimination to discover the leak. Go to the TT hose and draw vacuum from each of its inputs/outputs. This will provide the general direction of the leak (if one exists).

Cheers,
Joe

JM993

GR beat me too it.

Tal (GR), hope you are well.

Cheers,
Joe

guards red

Hi Joe,

I'm very well. I've been following your progress on these threads with interest. You've now bought another 993 I see, well done that man!

Regards
Tal

skl2

Joe and Tal, thanks a lot for your continued guidance! I will pick up a mityvac and continue my quest on the vacuum system this weekend

skl

Looks like another project with the son this coming weekend after watching Korean F1 qually. Haven't used the mit-vac for a while will have to find it.
Be glad to help him with this as he's helping a lot in the restoration of the '73 914 and is always glad to help wash the GT3

skl2

Two questions:

1) As far as process for checking vacuum, what do you consider "downstream"? I know the tube you are referring to that collapses - do I remove one hose at a time from that and connect a vacuum guage? I assume that tube you are referring to connects directly to the check valve which is mounted on the tree?

2) If vacuum goes quickly when checking these tubes, wouldn't that indicate an issue before it even gets to the check valve? Or am I looking at this backwards?

Also, I just found a great post where you have some really good pics of your varioram out of the car. I see exactly what you are referring to regarding the check valve. Do you have a part number, as I might just order one so while I have everything apart I can have it ready to go if needed.

Thanks.