Jordan Thieme

I did an LS swap last year and am trying to figure out how to get the heat and AC system working. The easier part should be the heating system, so I will start there. I have the valve system installed and it works well to divert the hot coolant either back to the engine, or into the inside radiator. The problem is that I do not have vacuum, so I have to use zip ties on the valve system to turn the heat "off". I am thinking about just using an aftermarket vacuum pump, but was not sure where to hook it into the system.

Once I get this working right, I will start working on the AC system.

As always, I appreciate your input and help!

gazfish

Would have thought the intake manifold has a vacuum source somewhere. Did you keep the vacuum reservoir when the swap was done?

Jordan Thieme

I could probably tap off of the vacuum from the intake. I should mention that the engine is an LS3. I have no idea where to tap into the vacuum on the 928 side of things.

Speedtoys

You dont have vacuum, OR you dont have the OE HVAC controls?

Hey_Allen

Or he just hasn't joined the two yet.

There should be one vacuum house running through the firewall that supplies the HVAC controls with vacuum from the engine bay, after a check valve. If I remember correctly, it's near the breaker booster vacuum hose, but I haven't looked at the vacuum plumbing on my 928 in a good while so I might be missing that up with one of my other car's plumbing.

JJ928S4

Do you have any of the original parts left over?

Mrmerlin

post a few pictures of the engine so we can what your working with

Jordan Thieme

Below are some basic images. I have all of the original HVAC controls still and they seem to function. I can change the fan speed, but the heat never turns off and the air diverters do not work. I am pretty good with mechanical stuff, but have never dealt with HVAC controls in a car or with vacuum so am pretty lost on how it all works. I appreciate your input and help. If any other photos would be helpful, just let me know and I can take more.


Overview of the engine.

Close up of area around brake booster.

Heating valve area.

Vacuum line at back of engine bay. This goes from the heater valve (to the left) and into the firewall with the original tubing (to the right)

Eplebnista

Anything downstream of the throttle body should be a good source of vacuum. There should be a port on the passenger side right after the throttle body for the EVAP system. If the computer you are using has a provision for controlling an EVAP purge solenoid you could hook the gm solenoid up to the 928 system inside the front passenger side fender. You could run a tee off the line in between the port and the solenoid to the vacuum reservoir inside the driver's side fender and then connect to the HVAC controls. You also have a big port on the back of the manifold for the brake booster. You can plumb into that line as well. Use check valves as needed to maintain vacuum in the booster.

Speedtoys

Ok, you need to fix all of the leaking vacuum actuators in the dash that are part of the HVAC system...you get no vacuum because it's all an open leak.

linderpat

As an aside, where is the blue hose from the brake MC? Does the conversion somehow eliminate that?

Jordan Thieme

I am feeling like I might need to just take it in to a shop because I am totally lost trying to follow all of the hoses.

For the blue hose, did there used to be a blue hose to the brake booster? The is an open vacuum line just under my brake booster where two hoses come together into a splitter.

I should mention, I have been driving the car for a while, so it drives well even without any of the vacuum lines hooked up.

Eplebnista

The 'Blue Hose" has nothing to do with vacuum or any connection to the engine. In manual transmission 928s it runs from the brake master to the clutch master.

If you find a shop that will touch "somebody else's project," than more power to you. We can help you out here on what and where on the 928 vacuum is needed for HVAC, EVAP etc.

Beyond that, this is the forum you want to search in and maybe ask questions - LS Swap Forum

Pictures of every port you can find will help as well as what model year your LS3 is. My knowledge is limited but I think you should have a big port for the brake master in the back center and a smaller port near the big one. You should also have a PCV port near the rear drivers side valve cover, another one on the front passenger side and two ports on either side of the intake just behind the throttle body. The only thing really noteworthy about the LS is that it may also have a steam line on the passenger side that plumbs into the radiator.

We would be a better source if you were putting a 928 motor into a Camaro instead of the other way around. The 928 vacuum plumbing is a bundle of snakes compared to the LS. Nonetheless, I am jealous to a degree because my dream is to put an LS3 into a 944. All I lack is time, money, a donor 944, an LS3 and buy-in from she who must be obeyed. 944's have caught on, so finding one cheap ain't gonna happen.

linderpat

So this car is an automatic then?

Jordan Thieme

So this is going to get tricky. The car used to be an automatic and I converted it to a manual, but the transmission is now a T56.

I absolutely love driving my car with the LS3, but it has been a long road to get here. I will definitely check out that forum. I think I found a good spot to get the vacuum on the throttle body of the LS3 engine, but I have no idea where to begin with tapping it into the Porsche system. I am thinking I will start by capping off anything I can find that is open and hopefully someone can help me understand where the best place to hook into the 928 system is.