Vacuum Leak Testing Smoke Machine

I watched this video from martinbuilt showing a DIY build, after seeing a pro grade unit being demoed used by the Car Wizard in his essential shop tools video. The cheapest commercial smoke machine I could find is about £180, so a DIY one is much more suitable for the few times I’m likely to need this like I did today.

This ones diy with a bit of design flare to it, only because of the fancy oil container I found on amazon.

I built this last year but this is the first time I’ve been able to use it to test a problem on a car.

Chopped the top off (it’s not very air tight unfortunately, but good enough).

Mock up using some foam a lid with two electrical connection and two tyre valves.

Cut out an aluminium blank to use for the new top.

Foam design revisions 2, move some things around and put in the original fill lid to make it easy to put the white mineral oil in.

Cut all the required holes into the blank.

Mounted all the hardware and added a wick and some resistance wire. These will generate the smoke, as the resistance wire heats at lot and the white mineral oil smokes when it’s heated.

Tested the resistance wire, pulls 5 amps at 12 volts.

Assembled, the lid is not a 100% seal but that does avoid an over pressure situation.

First smoke during testing!

Had a good chance to test this, we’ve got an E36 Compact with an M52B28 engine swap done many years ago. The engine has been idling high randomly, normal RPM with the MAF off. This suggested a vacuum leak, but the question was – where is the vacuum leak. Did try changing out the idle valve as we’d picked up spare on ebay but that didn’t help.

So we used this setup to test and find the leak. First pulled the airbox so there’s more room.

Hooked the plus and minus up to the car battery, ran a tyre inflator into the smoke machine. From there put a latex glove over the maf and poked a brass pipe into it. Theres a rubber pipe from there into the smoke machine.

As there was quite a bit of smoke coming out of the tin I added a load of tape to reduce that.

Started to see some smoke waft out from under the intake manifold. 

Took the pipe off the alternator for a better view.

It was clear then that the smoke was coming from the crank case pressure regulator valve. Time to order a new set of hoses and the regulator valve.

Some testing on video:


Rear Brake Pressure Regulator

Someone pointed out the stock BMW rear brake pressure regulator was incorrectly mounted on the car. Not sure if this made much difference as it has always worked. However decided to fix this and add some adjustability if needed in future in the form of a Wilwood Brake Proportioning Valve.  The wilwood valve part number 260-12627 has M10 threads so the existing pipe fittings could be used.

Marked up the position for the first mounting hole.

First hole drilled, inserted a rivnut here.

Test fit, checking alignment for the top hole.

Both holes drilled and rivnuts inserted.

Final fit of the Wilwood valve.

The inlet and outlets are in roughly the same place as the old valve which will make moving the hardline easier.

Removed the P clip holding the pipe and added two new bends bringing the pipe up to the new valve.

View from above – it’s easy to get to and make adjustments.

The input pipe from the master cylinder is a braided flexi pipe which made installation easy. Lining the threads up too some effort as the tolerances are really close.

Close up view from above.

The final step was bleeding all four corners, replaced the fluid throughout as it had gone quite dark, photo shows the old colour. New fluid is much clearer.

Not done any testing/setup yet as it was raining all day.


Blue! And oil pump

Silver is so last month, so blue it is this time!

We used red hamerite on the exhaust plugs and those didn’t discolour until we welded something on it – so it seams heat resistance enough!

The hammered blue looks great out in the light.

Oil pump disassembled and cleaned. It all looks fine nothing really worn so no need to replace it.

The parts slot right into place, covered in assembly oil. This stuff is thicker than normal oil and kinda sticks to everything. Should help keep everything lubricated on the fist run.

The filter element has a few hardended clumps inside it but nothing major!

Engine Work

M52 crank sits neatly into the M20 block

M52B28 crank shaft sitting in the M20 block – this end will need some kind of spacer for the oil seal.

Crank sits in the block like it was meant to be there – only other thing that need to be tested is the M20B20 130mm conrod with the M20B25 pistons in place to check clearances.

One more picture for good measure!

One question, how the h*** to do you the cam belt pulley off the crank? It seems to be wedge solid. The cam chain pulley came right off the M52 crank so I assume its the same with the M20 except I’ve got 20 years of gunk keeping it on!


Fuel Tank

Today we installed the fuel level sender in the fuel tank – sounds easy but it took most of the day! Stage 1 was to figure out the numbering system as the chart that came with the sender only when down to 180mm deep tanks. The Marlin tank is 160mm. Luckily it was quite an easy one to figure out – 160mm depth, 67mm pivot, 63mm radius.

Click me

Next on the list was to make the hole that the send goes in. It was all going well until the dremel (110v 20 odd year old model) finally giving in and died leave the rest of the cut out and clean up to me done by hand. Still turned out quite nicely:

Click me

There was a lot of mess in the tank, but luckily one of the vacuum cleaner attachments fits in the hole!

This only leaves figuring out how to attach the fuel hose to the tank and mounting the filter/pump!



It took 2.5 years to build the car and pass SVA (now IVA) and a lot longer to get to where it is now! To see the Sportster out on the road have a look at one of the videos here.

During 2008 we rebuilt the BMW engine from 2.5 to a 2.8 creating an M20B28 stroker engine. It uses the crankshaft from the later BMW M52B28 and the conrods from the M20B20. Not much more work is needed other than a clean up, slotting those bits together and a crank spacer. To read about the engine build click here (very picture heavy!)

In March 2009 it was painted, a full set of images is here.