I’m in the midst of getting my car ready for a family vacation.
I have always had an issue with and oil leak from my banjo bolt located right up against the firewall on my MK IX. Today I decided to take it all apart and see what was going on. To my absolute horror, when I unscrewed it, it was filled with all of the threads from the soft aluminum head. It is completely stripped.
Short of taking the head off, is there anyway that I can get this car running until the end of summer when I would take the engine out? I am supposed to be taking the car on a holiday on Sunday. The last holiday I took with the car ended up having to be towed home and we canceled the remainder of the holiday. My pride cannot handle another incident like this! (not will my wife’s patients…)
Hoping for someone with a little bit of good news to get me through the holiday,
Same thing happened on my 120. I made a 1/4" longer bolt. You need to get a tap in there to tap the threads deeper, and be sure to load the tap with grease so you pull out all the chips. You don’t want them getting in the oil passage there. As I recall the tap was either 5/16-18 UNC or 3/8-16 UNC.
Unfortunately, the bolt is already a very long one. It is already 1 inch of thread. It must’ve stripped a few times previously in its life as the stripped aluminum was only on the last 1/4 inch of the thread.
Unless anyone has any other ideas, I think I will cut up a tap to make it short enough to fit behind the engine and see if I can carefully fit a larger bolt in. I like the grease idea to help keep the shavings out. I was thinking I’ll do a quarter turn and remove it so I can suck out shavings. I’ll first spend some time machining a larger banjo bolt.
If you pop off the cover, cam caps and cam, you can flush out the input port to ensure you haven’t missed a shaving which could end up being pushed through with very bad outcome. I haven’t had to resort to using anything longer than the standard bolt. I thought the repair bolts were longer than an inch though. It would be worth a call.
Most importantly, the reason this happens is over torquing to try and staunch a leak. If you use the proper super thin washers with a crush ring you can seal them with very low torque so long as the mating surfaces are flat. Too many people are using thick copper washers, and trying to seal against imperfect surfaces. A little Hylomar on the washer can’t hurt either.
I’ve had a look at my Stype head today and the depth of the hole is about 40mm on the exhaust side and a little bit more on the inlet side because the head has a bit more metal at the back for the tacho drive.
The thread is 5/16 UNC.
Jeff, thank you so much for your picture of the bolt. Yours was a quarter of an inch longer than mine, and that gave me enough length to get mine to seal again. I thought mine was already at the maximum length, but obviously it was not.
I am just confirming that the oil intake’s from the end of the bolt, because the bolt is within a 16th of an inch from bottoming out right now. I made my own banjo bolt, and tried to make sure that I could get every bit of length on it that I could.
Am I correct that if my banjo bolt is too long, or is clogged, that I would be able to see that there is less oil when I open up the valve cover?
Thank you to everybody for your help. I had already made an oversize bolt, and was trying to figure out all of the ramifications when I got this picture. Luckily, I have not altered anything on the car.
It just did 300 miles through the mountains, with no problems. I did notice a slight drop in oil pressure while going up the steepest hills, but will start a new thread to ask the question.
