Lower balance shaft leaking

js86944 · 08-12-2010, 08:12 PM

Today was the day we started up the 944T, after replacing the fuel lines which were leaking. Once fuel pressure was built up, it started and we idled it for 10-12 minutes at 2k rpm. The car has half a tank of fuel since October of '09 so about 10 months old. 1/3 can of seafoam was put in a few days ago when we were going to start it and so today it smoked heavily while we idled. I figure that this is to be expected from the old fuel with the addition of seafoam.

Now, after we idled it and the fans kicked on when we noticed a stream of oil from the front passenger side. At first, we thought it was the oil filter but that was not the case. We suspect the leak is from the lower balance shaft seal which is new as well as the o-ring, sleeve and the onion seal. The leak is from behind the timing cover and in front of the housing. I have not taken it apart yet and want opinions and what is the best way to attack this issue. I want to remove the least amount of parts. Why would the seal/o-ring/sleeve or whatever is letting oil by fail after 10 minutes? What can I do to pinpoint the leak without turning the engine on again? I will take it apart tomorrow afternoon and post an update. 10 months of work for nothing

- Is there something I could have done wrong during installation?

89-944NA · 89-944NA's Garage

damaged the onion seal or o-ring.

js86944 · 08-13-2010, 03:33 PM

Well, today I began to take things apart and so far so good. First, both drivebelts and the power steering pump, zip tied it to the spring on the passenger side. I then removed the sprockets and balance shaft belt. I will gather a puller for the crank pulley tomorrow and then the timing belt will come off so that I can remove the rear timing cover. The good news is that I removed as little as possible. The only pieces I removed from the top of the engine was the distributor cap and rotor, nothing else. I moved the A/C compressor out of the way to remove the fan assembly through the bottom to give me room to pull the balance shaft housing. It was very easy, however, I want to know what all should I be looking for when I remove the lower balance shaft housing? What will let me know that I tracked the leak correctly when I pull the housing?

I plan on replacing all four seals on that lower balance shaft and use loctite 674 on the housing. I still want to know why something like this would fail. I'm wondering is it because the seal was not OEM and instead an aftermarket one from LR. I will update on Sunday, thanks.

Inspector 7 · 08-13-2010, 08:46 PM

The first time I did the balance shafts on my '86 951 I had a leak from the lower balance seal. I replaced the seal, onion seal and the O-ring and the leak persisted.

What I found to be the cause of my leak is the plug inside the balance shaft under the bolt that holds on the pulley. The inside of the balance shaft is used to carry oil to the bearings and is pressurized with oil. There is a small aluminum plug that is pressed in to prevent the oil from escaping. Mine had loosened and was allowing the oil past the plug and then past the threads of the bolt.

I tried re-seating the plug, but that didn't hold. I ended up using Loctite green hydraulic sealant on the bolt threads and haven't had an issue with leaks for several years now.

That's my experience.

nize · nize's Garage

on a similar topic, does anyone know if the upper balance shaft (and cover) is removable on the 951 without removing the turbo?

running_cold924 · running_cold924's Garage

mine was leaking from the metal sleeve and after doing it twice, I figured that out...

js86944 · 08-14-2010, 08:09 PM

I removed the crank pulley, timing belt and the rear timing cover tonight. I discovered that the lower balance shaft spins with the sleeve, in other words, it does not spin freely of the sleeve like the upper balance shaft. I am able to spin the top balance shaft free of the sleeve and vice versa whereas on the bottom balance shaft they spin together. What would cause this and what is the solution to this? I am guessing that the top balance shaft is in order and the bottom one is not. Would the wrong seal cause this? Could it be that I used the bigger seal on the lower housing and the smaller seal on the upper housing? Either way, it seems that this leak is due to my error and I will be ordering from PP - OEM only.

js86944 · 08-14-2010, 09:12 PM

I took a look at the seals on both balance shafts and they are both in their proper place so no error there on my behalf. The lower balance shaft seal says 30 48 7 which matches the dimension listed in the PET catalog. The upper balance shaft seal says 30 47 7 which also matches the dimension listed in the PET catalog. I now suspect the problem is the sleeve since I have the issue I explained in my previous post. I'm hoping that the sleeve was machined wrong and this is why the shaft does not spin freely of the sleeve and does not auto-center like the upper balance shaft.

bebbetufs · bebbetufs's Garage

If you somehow mixed up the sleeves you may have put the cam shaft sleeve on one of the balance shafts. If I remember correctly there is a very small size difference which would cause a leak.

There is a mylar gasket (almost invisible and wafer thin) between the sleeve and the step on all the shafts. Did you install them? When the pulley is properly torqued onto the shaft it squashes this gasket between the sleeve and the step on the shaft and prevents oil from seeping past it and out onto the pulley. If you have taken the pulley of the shaft again you should use new mylar seals. They are not reusable.

js86944 · 08-15-2010, 09:18 AM

I installed every seal as shown in the PET, torqued as well. As far as the sleeves go, they are all the same part no. according to the PET, so I doubt they could have been installed in the wrong place. This leads me to believe the sleeve I received was incorrect and therefore does not allow the shaft to spin independently of the sleeve. I will remove the housing tonight to see if the o-ring or the onion seal failed, but I'm quite confident that the sleeve is my problem. I will be ordering a new sleeve and the three seals on Monday from PP.

bebbetufs · bebbetufs's Garage

Ok. Come to think of it the old sleeves on my car had a definite difference in size. However the replacement parts ordered from pelican where identical. I have no leaks.... Sorry for the confusion caused and good luck with the new sleeve.

I'm not sure about this, but I've heard that belts do not like oil. If you got any oil on your balance shaft belt you might want to replace it.

Techno Duck · Techno Duck's Garage

The front sleeves for the cam and balance shaft are slightly different sizes and can be mixed up. The other thing to check the bearing shell that is pressed into the power steering bracket. When these get worn they will cause leaks also.