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Push Rod Tub Leaking in cylinder head R75/5

4

44006

Member
I have an oil leak from the joint where the push rod tube which passes through the head enters the rocker area. Oil works its way down the outside of the tube and drips off in the area between the fins on underside of the head (onto top of boot).

Definitely no leaking at cyl to head joint.
Definitely no leaking at head to rocker cover joint.

About enough to saturate a paper napkin shoved into fins in about 200 miles (once a day diaper change for this day ride bike)

Has anybody had any luck sealing this tube to head at the rocker box end from the rocker box without removing the head?
 
No because it's impossible.

Think of this as periodic maintenance, i.e. every few years you'll need new pushrod tube seals. Cost of doing business/part of BMW ownership. Don't worry/be happy.
 
Like Kent says. I'd bet a dollar to a doughnut that the push rod seals (at the crank case) are also in need of replacement.

It was occasional practice to drive the push rod tube(s) down against the seals to stop a leak at that joint. There is a "ring" on the tube that bears against the crank case seal; on the "early /5s the ring was pressed on and could be displaced to compress the seal; but on "later" models the ring was brazed on. The affect was the same, but when these later tubes were driven down the push rod tube was driven with it ... essentially "pulling" the push rod tube out of the head. Leak transferred to the head-end of the tube.

At best this whole practice was a stop gap... they always start leaking again.

It's time to pull the heads and replace all of it.

Here's a great tutorial...
 
Remove the pushrod and clean the tube/head junction with a squirt of brake cleaner. Then with the bike laying over on the opposite cylinder so you can see and have better access, apply wicking thread locker (green) around the end of the tube. Let it dry and you are done.
 
The last time I looked the pushrod tubes are not connected to the head. They are an interference fit in recesses in the cylinder. Sometimes they migrate a bit up into the cylinder. Sometimes they just get loose.

I concur that green wicking thread locker placed around the tube with the cylinder arranged nearly upside down so the tubes are sticking straight up may work. I would warm the joint with a heat gun and then apply the sealant.
 
There are two short pushrod tubes in the head of of my '72 /5 motor. They run from the head/cylinder interface to the rocker arm area in the head.
I just went down in my basement shop and looked at a set of R90S heads, they also have the two short push rod tubes described in my earlier post.
 
"Remove the pushrod and clean the tube/head junction with a squirt of brake cleaner. Then with the bike laying over on the opposite cylinder so you can see and have better access, apply wicking thread locker (green) around the end of the tube. Let it dry and you are done. "

Thank you George - you were the only one to understand the question - I will try your method when I do the periodic valve adjust due in the next few days. This is the second time in 3 years I have had one of these older bikes pissing on my foot from these tubes that pass through the head.
 
temporary fix

I had a /6 that started to seep too. I bought some Lucas oil treatment and it swelled the old ring enough to stop the seepage. It was still not leaking when I sold it 3 years later.

I am sure any of the oil treatments that advertise the ability to stop leaking gaskets will work...temporarily.
 
The rocker arm stand o-ring seals a completely different hole through the head.

The leak being discussed is around item #5, the "protection tube".
 
Lucas:)

Good products for tired engines and others too. My /7 has the same issue, leaky tubes at heads:(. I will try same, as my engine may be tired at 377000m.:):usa Randy
 
Problem solved - the pushrod tube that passes through the HEAD was leaking
=============================================================
Removed rocker assbly and pushrod and close inspection revealed a tiny rub hole in the top of the pushrod tube that passes through the HEAD.

Cleaned throughly with carb cleaner as if cleaning a gun barrel

Used half of wood clothespin (non spring type) as tool to press and work a small amount of JP weld into the small rub hole and light smear in tube over the area

Reassemble and tap the rocker assbly down farther on its posts to get more clearance

4000mi on - no more hint of leaking
 
I tried the method of fixing a leak at the protection tube of my r75/5 by laying the bike over cleaning it with brake cleaner and applying Loctite 230. I thought it had worked but after 1k I got a drip. I will probably try it again before I pull the head. Is the protection tube the same size as the stand supporting sleeve? Can I use the same drift to remove and replace it. Should I use something on the contact surface? Thanks
 
Last edited:
44006 said:
"Remove the pushrod and clean the tube/head junction with a squirt of brake cleaner. Then with the bike laying over on the opposite cylinder so you can see and have better access, apply wicking thread locker (green) around the end of the tube. Let it dry and you are done. "

Thank you George - you were the only one to understand the question - I will try your method when I do the periodic valve adjust due in the next few days. This is the second time in 3 years I have had one of these older bikes pissing on my foot from these tubes that pass through the head.
Click to expand...

I have had success with cleaning the area and applying a small bead of J-B Weld. The third fix-all behind WD-40 and duct tape.
 
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