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My friend owns an XK 120 with XK 150 motor, gearbox, and front disc brakes. It has the Brake Servo under the left hand fender and the Vacuum tank under the right hand fender and the copper pipe running from the servo to the vacuum tank. The vacuum tank has the vacuum tank valve on top with the line from the servo connected but the other connection on the VT valve is open to atmosphere. I assume a line from there goes to to a vacuum source on the intake manifold some where but we can't find where it would be connected. The engine idles and runs fine, so clearly there is no open port on the manifold that we've missed. does anyone know exactly where the vacuum line would attach to the manifold? Thanks for any info.
Clive
XK 150s had 4 versions of the engine possible. That said all of them had a vac. port on the rear of the intake manifold. Depending on what manifold you have you need to look on either the rear of the manifold or if your manifold came from a 120 look underneath. A picture of the manifold would help with guidance. Best.
That looks like a manifold from a 420 sedan. It also looks like the vac. port has been blocked off on the bottom with a plug and JB weld? It is heavily modified as all of the ports are closed for the auto choke--or this is from something we do not recognize. Those are HD8s right? At this point I would try to clear the port where the plug is and use that. BTW the picture of the reserve can is too small--that was the vac reserve for the 420 and 420G MK10 and others but it only provided vac for the climate switches. You need a vac bottle for a MK2 or S-type. We have one in our E bay store #2. Hope this helps.
Thanks so much for your input. Not sure what a HD8 is and the vacuum reserve tank is under the rear of the right wing/fender, so I'm a bit confused as to what you mean by being too small, as I didn't post a photo of it. The servo unit is located at the rear of the left wing/fender. a 3/8" copper line runs from the servo unit to the vacuum tank, which has a 2 port valve on the top, and connects to 1 port. The other is open to atmosphere. I assume this port should connect to the inlet manifold somewhere.
Thanks again for your help.
The component I have are as below.
HD8 refers to the size of the carbies i.e. 2-inch throat.
SU carbies refer to the number of 1/8 th inches above 1 inch. e.g. HD6 is 13/4 inches. HD8 is 2 inches. The D refers to the diaphragm mounting of the main jet.
Note. That heater hose exiting the rear of the intake manifold is looking a bit "gnarly" and should be replaced.
Not sure where the image came from but no matter. The tank you have in the drawing would be correct. Just curious as to why your friend has all of that plumbing.. On the 150 the vac. bottle was mounted with the booster so that there was only one line from the manifold to the tank.
Yes, this is quite a mystery, so from what I have learned so far is that the manifold is probably from a 420G and that those copper "plugs" shown in my photos of the underneath of the intake manifold are probably where the source for the vacuum would be attached. As the manifold is also connected to the radiator and subsequently the heater, we were worried that removing one of them would create a water leak. Currently we have disconnected the servo and vacuum unit from the braking system and bled the the lines and we are getting a much better brake pedal feeling.
Thanks for all the advice.
Clive
07-22-2024, 07:04 PM
XK 150 vacuum routing
