Sentra head gasket dilemma

As I've said before, my intent is to sell my turbo Sentra at the beginning of next year and purchase a Focus RS. I've also spoken about my coolant loss issue. Well, just in the last week, the Sentra has had a misfire for the first few seconds after startup, and sometimes throws a P0300 (random multiple misfire) code that comes and goes. Researching this, in combination with the slow coolant loss, leads me to conclude that there is a small amount of coolant leaking into one of the cylinders (#2, most likely) that is causing the startup misfire. It appears as if the head gasket is leaking slightly.

Thus the dilemma. So here are my choices:

1) Repair the head gasket now and ask top dollar for the car in January.

2) Nurse it along until January and sell it privately with full disclosure, asking a lower price to compensate.

3) Nurse it along until January and trade it in, taking the typical low trade-in value hit.

The problem with trying to run it until then with the leak is that I run the risk of catastrophic bearing failure due to oil contamination, possibly reducing the car's value to near zero. I guess my first step is to do a leakdown test to confirm the diagnosis.

Opinions, please?

Well.. There's always this stuff.. It would make nursing it till January much easier, especially since you seem to have recognized the warning signs before the gasket has completely let go. If your leakdown test indicates a blown gasket it's something to consider, karma notwithstanding.

Blue devil is the E36 M3, there's also some "nano particle" stuff in a grey can I think that also works very well. They are both like 40 and 60 bucks though but hey if done right sometimes it fixes a head gasket for an undetermined amount of time, without the use of a wrench!

Meh if It were me and I had the time I'd just replace it, not worry about limping it and then not worrying about selling it cheaper or whatever

We used blue devil on a lemons car (a 6 cylinder e36). Fixed our HG in an hour, and we proceeded to beat the crap out of the car (redline, full throttle) for the next 17 hrs straight (it was a true 24 hr race). Then we rented the car to another team (full disclosure) and they raced it a whole weekend without issue. Then they bought the car from us and I know it raced at least one more weekend with them without issue before I stopped hearing about the car.

I highly recommend.

Wow, great idea, guys - thanks! I will get the leakdown test done first, though.

Leakdown test probably won't tell you much. You are talking about a leak that pushes a tiny bit of pressure into the cooling system when the cylinder fires. I think it will be much higher than the 150psi you can get out of a leakdown tester.

You pretty much have your diagnosis anyway. Look at the plug when its cold, and you will likely find it damp.

Unless I am missing something, I can't imagine that.

1. A turbo Sentra with a bad head gasket would trade in/sell at any more than scrap value.
2. Swapping a head gasket on a Sentra would take more than a busy weekend.

^^^My thoughts as well. Removing the head shouldn't be more than a couple hours. Slap a new gasket, and upgrade the bolts/studs while you're in there. Then crank the boost up a bit more and have fun for another couple months before selling.

In reply to jstein77:

I agree on doing the leakdown test. And I agree you may find a wet spark plug when you do it. I know nothing about Sentra engines but I know on some engines (my Ford 4.2 for example) there are coolant passages from the head to the intake manifold, and a leaking intake gasket can allow coolant into the intake, even after the engine is stopped.
If much coolant leaks into a cylinder while it is stopped you risk hydro-locking the engine when you try to start it.

Back when I had my SE-R, anyone who wasn't totally out to lunch knew a turbo'd QR either 1. had ARP studs and a multi-layer steel head gasket OR 2. needed ARP studs and a multi-layer steel head gasket. You're never going to get decent money for a turbo'd SE-R from anyone other than an enthusiast. If the job is within your mechanical abilities, I'd say do it. If it isn't, it might be time to eat the loss and sell it "as is" with disclosure to someone who can do it the job. You'll never get the money back out of it that it will cost to have it done as a shop job.

Or you could take the "craigslist approach" and buy the parts, decide not to do the work and do an add that says "Needs head gasket, have MLS gasket and ARP studs. My mechanic says easy job. My loss is your gain".

Well, I pulled the spark plugs this morning, and didn't find any moisture:

Number 3 is a little sootier than the others, and #4 is a little cleaner, but nothing conclusive. I adjusted the gap, put a little anti-seize on them, and reinstalled them.

The oil looks fine; no signs of water and exactly the right level.

Leakdown test is my next step.

On a related note, one of my local dealers is listing a blue RS on their website. No picture yet; must still be in transit.