Porsche 914 2.4L oil leak??? Rebuilt engine Twice????

[schantzmd]

I just wanted to see if anybody else has had this problem. I have a fresh rebuilt 2.4L type 4 that I built last month that has cast steel 104mm P&Cs. After 15 min of running it developed an oil leak around the base of the #1 cylinder to engine case mating surface.

I tore it down again last week and resealed it, fired it up last night and after 15 minutes the same darn oil leak at the #1 cylinder popped up again.


Here's what I know.


The leak is only while the engine is running.

The leak is not from the push tube seals.

The leak is not from the oil galley plug under the #1 cylinder.

The leak volume is about 1 drip every 30-45 seconds

High Temp silicone was used around the base and side skirt of the jugs.

None of the other 3 cylinders leaked during either build.

The heads were torqued to factory specs.

The case was freshly machined for this build.

No cylinder base gaskets were used due to the large 104mm jugs.

Just looking for some advice. I've built over a dozen stock and mild type IV's but this is the first time I've ever had a leak like this. This is also the first time I've gone with a 104mm P&C set. I'm just wondering if I should try to retorque the heads to maybe a little extra or if that might backfire on me. Any help or comments would be greatly appreciated.

P.S. I also have this question in the type4um, just thought having 2 post up might help.

[Piledriver]

Welcome to the forums!

Did you have the block decked true to the crank CL?
(Should have been done when bored, but not certain)

Did you make sure there were no burrs raised when the studs went back in? (might help to countersink the holes just a hair)

Did you measure the length of all 4 cylinders?
(No, seriously, check that)

That's not an uncommon spot to see seepage on high mileage motors, but an immediate leak is not typical.

Iron 103s etc make for a lot of case pressure, so if it can leak somewhere, it will. There are better choices...

You only want a smear of silicone, any more will end up in your oil screen at best.

If it was near #2, I'd suggest making sure the thermostat pulley bolt was in, that has gotten a few of us over the years myself included.
(It goes all the way through on most cases, no bolt==oil leak)

[schantzmd]

1)
Not sure about the block being trued to the crank when it was machined but Carcraft said that everything checked out good when they inspected it and opened it up to accept the 104mm jugs.

2)
Checked for burrs and cylinder mating at and all were flat and flush (I might try the countersinking idea though)

3)
Checked the height on all 4 cylinders and they all measured <=.001"

4)
You're right about the thermostat bolt, that got me too, years ago on my second type 4 engine build, gotta love that bolt hole!

Thanks for the idea on the counter sinking, I think I'll give that a shot when I tear this back down,... for the third time,..... I always inspect, replace, or resurface everything in my engine builds and I hot test them for at least 2 hours on my test bench before I install them to hopefully prevent problems like this.
This is the first time I've gone with these big 104mm jugs so I didn't know if there was something I was missing or doing wrong, especially since the mating lip between the cylinder and case is so thin. I've never had a reoccuring problem like this on a type 4 although before this the largest P&C set I ever used was a set of 96mm's which still left a lot of lip at the cylinder to case mating point.

Since this happened twice my main worry was that this case might be screwed up at the #1 hole, I don't know how it could be but stranger things have happened.

Thanks again for the advice!

[Type 4 Unleashed]

I've read thru this, and after thinking on it a bit, have some things you might want to check.

I've used the large bore cyl's a few times, and have found the holes for the head studs need to be opened up. I mock up each cyl in each hole, then mark each cyl to be sure it goes back in that hole, after the holes are clearanced for the studs.

You could have 2 issues, one could be the head studs may not have been installed far enough back into the case, and the cyl is hitting one of the studs at the taper from the threads.

To make it easier, I'll explain how I prep the cyl's for use: First there is clean, clean, clean, then I install the head studs then I clean again, and I make sure all the studs are installed far enough into the case, and that means all the threads are now in the case and the last threads actually sits below the deck now. You have to remember, there wasn't am issue with the 94 or 96mm cyl's, they were no where near the cyl studs, well they are an issue with the 103mm cyl. And for reference any cyl over 103mm, is a bored out 103mm cyl.

Now I have all the studs installed and they are down far enough not to interfere with the cyl.

Next step. The stud holes in the cyl's are not exact, so I move the cyl's around till I find where they fit the loose's, then I mark the cyl's to their position. Then I start clearancing the stud holes until I can get the cyl to sit flat on the case deck and I am able to slightly rotate the cyl left & right. And have found some times, I have had to clearance the spigot of the cyl where it seals against the head.

Let me say this again, the holes have to be clearance enough to be able for the cyl's to sit flat and to be able to slightly rotate the cyl;s left & right. Other wise the cyl's will bind against the studs when you torque them, and could tilt the cyl, possibly causing a leak, not only at the base but also where the cyl seals against the head.

Another thing to look for could be a crack in the case, but that I think is unlikely, more likely though could be a hair line crack in the cyl, I have found a few AA cyl's with these cracks, and it is towards the bottom of the cyl's where it is the thinnest. And your leak doesn't start untill the cyl starts expanding form heat.

[schantzmd]

Thanks for the advice. I know that the taper of all the studs are flush and/or below deck height so that rules out #1. You might be onto something with your #2 idea though. I'm going to check that out when I tear this thing down,...again,.... LOL. Anyway thanks for the idea. I've never had a reoccurring problem like this with any of the other type IVs I've built but like I said this is my first experience with the "Big" jugs.

Anyway, Thanks again!

[Type 4 Unleashed]

Thanks for the advice. I know that the taper of all the studs are flush and/or below deck height so that rules out #1. You might be onto something with your #2 idea though. I'm going to check that out when I tear this thing down,...again,.... LOL. Anyway thanks for the idea. I've never had a reoccurring problem like this with any of the other type IVs I've built but like I said this is my first experience with the "Big" jugs.

Anyway, Thanks again!

Don't completely rule out # 1, the studs installed far enough in the case is just a part of the assembly issue. sufficiently clearancing the cyl stud holes are just as important.

Well your pulling it down again, so you have some ideas now what to look for.

And the only reoccurring problem I have with big Type lV's is not enough money each time ...

[schantzmd]

Thanks for all the advice guys!

I tore the engine back down, reinspected the mating surfaces and studs on the engine case, and reinspected the cylinders. Everything looked great on the case but I did notice a small perpendicular nick on the #1 cyl jug's mating surface so I used your guys' grinding compound trick and voila', no more leak!

I guess this was just one of those jobs where the third time was the charm.

Thanks again!