Car has been laid up nearly 2 weeks now for a stinking head gasket replacement, mostly due to waiting on parts, and I keep finding stuff that needs to be replaced.

I was searching around about preparing the block surface (which stayed in the car) for the new head gasket, and came across a thread on a Porsche 944 forum where these several posts were made on the same subject:

Well since I've been waiting on stuff, I've fiddled with the block and pistons here and there. I used a bit of Seafoam on the tops of #1 and #4 pistons, and I think I disturbed the carbon rings around the tops of #2 and #3 cylinders. I was planning on bringing 2 and 3 pistons up and cleaning those here soon.

What should I do? Is my engine block destined for failure? Before the HG sprung a leak, the engine was consuming just 1 quart of oil in 6,000 miles, and that's with 329,000 miles on the block and all the internals.

I **HAVE** to get this car back together now, this week hopefully. My wife and I are driving it to the beach in just a couple of weeks (taking our bikes and the bike rack will only go on this car). So I don't have the time or money to be pulling the block/trans, or doing much of anything really with the block internals.

Thoughts?

 

what motor is this op?

 

I really doubt you have caused any harm to the cylinder or pistons. Just try to keep it as clean as possible and use common sense. Getting bits of carbon stuck around the ring area is a risk but it does not guarantee failure.

One thing however, a freshly rebuilt head on a older bottom end does tend to make the engine consume more oil. With the top end tightened up it can increase the vacuum and put more work load on the ring and cylinder seal.

 

Really the only thing REPLACED in the head is the valve seals. The valve seat surfaces on the valves themselves had a little work, but I already had compression numbers above 240 before I started this work so I would guess that valves were sealing pretty well.

It's a B18C1, all original at 329K miles when I pulled the head 2 weeks ago, first time the internals have ever been exposed.

 

Not a problem.

 

aite, well, sho'nuff the engine consumes more oil now. It's taking down a quart in 3K miles, instead of 1/2 qt in 3K like it was before the HG blew.

Also my MPG is down from where it was before. Was getting 29-30 before, now it's more like 26-27. Not sure if the O2 sensor might have been fouled from all the burning coolant going through the exhaust, or if it's because of the oil consumption. Maybe a new O2 sensor would help?

A quart in 3K miles isn't such a big deal, though. I buy the 5-qt oil jugs and put in 4 every 6 months or 6K miles, and I can just top off with that last quart half-way between oil changes.

*edit* coolant usage is absolutely zero. Car hasn't lost a bit of coolant in 3 months, so I'm pretty stoked about that.

 

blown HG can damage an o2 sensor pretty easily actually due to all the steam going into the exhaust.

I'd say replace the o2 sensor and just go from there.

 

ya a qt every 3k miles is not a big deal at all. Shoulda been a given to replace the oxygen sensor, I'm really surprised you didn't yet.

 

Didn't really occur to me until I noticed the lower MPG, and now it's just been a matter of getting around to it and spending the cash.

 

Coolant absolutely destroys O2's and CATs. Dont be surprised if you get a P0420 later....

 

The o2 sensor definitely helps with the gas mileage. As far as cylinders being scorched, I don't think you did any damage to them. You said that your compression results were pretty good, so I highly doubt that anything is wrong with your cylinders.

Seals should be pretty good, are you blowing out blue smoke on acceleration when it's cold ?

 

P0420 is an OBD-II code. I have an OBD-I car with only one O2 sensor upstream of the cat. And my area has no emissions testing.

As someone told me when I had the car apart, the work done to the cylinder head (making it seal tighter) is probably creating more blowby on the piston rings. I'm guessing that's what is happening. Don't know for sure if it's blowing smoke when it's cold, at least I'm not sure if it does while driving anyway.

 

Yes this is what I mentioned early in the thread. At that amount of miles its a shockingly low amount of usage but I assume you drive it fairly easy without constant flogging. The carbon deposits that form over time as well as general wear and tear of the rings will allow oil consumption. However they will usually blow good compression numbers and still have full power.