Headgasket? Wtf??

[GooeyGus]

Hey Guys,
I've been trying to track down the reason I am burning a tiny bit of coolant.

Here's where I was at so far:

Compression: Just under 155 all the way accross

Car was running great, never over-heated, didn't push coolant, coolant never bubbled.

No smoke out the exhaust while cruising or under boost.

When I start the car it would sputter a bit and one puff of coolant/steam would come out the exhaust.

I was thinking the FIAV could be leaking into the intake manifold.

Here's what I found today:

I went to mess with the FIAV and decided to check the oil. I just changed it two weeks ago and it was normal. Today, it was a bit cloudy. Not completely milky like a full-blown gasket, but definitely a little bit of coolant in there.

So next I decided to check the oil cap on the valve cover. Sure enough, a little bit of white foam

From there I decided to pull the plugs. All of them looked normal, except the number 3 cylinder was a bit more whitish. That sent up a red flag.

So I decided to shine a flashlight into the cylinder. Sure enough, I could see coolant on top of the #3 piston. I cranked the motor with the spark plugs out a few times to clear the coolant, and proceeded to compression test.

Compression is STILL perfect at 155 all the way across. No more then 1-2psi variation. The compression tester has been calibrated against NIST standards, so I know it is accurate.

I'm really confused on this one

My plan is to change the head gasket this weekend, as I already have all the parts ready to go.

BUT I wish that I could get some sort of verification that the head or head gasket is bad. I have a freshly rebuilt head ready to go on, so even if the head IS bad, it's not a big deal.

I just dont understand how the headgasket can leak into the cylinder (ONLY when the system is pressurized and the car is OFF, BTW. Doesn't blow smoke while cruising or under boost) and yet the compression test show that everything is perfectly normal.

Has anyone else experienced a failure like this?

 

[JEFFREYCASTGSX]

Even though you "see" coolant, i would do a leakage test first.

 

[viprez586]

Even though you "see" coolant, i would do a leakage test first.

+1 do a CLT.
With that compression I wouldn't worry unless your going through excessive amounts of coolant.

 

[GooeyGus]

Coolant use isn't excessive, maybe 1/4 gallon every month, but there is definitely coolant in the oil and coolant in the #3 cylinder.... I just don't know how it's getting there.

 

[viprez586]

Only one way to find out.

 

[Benshooter]

-head gasket
-cracked head
-cracked block(least likely but you can't rule it out at this point)

Pick your poison.

 

[IgotBoost91]

well if you just recently changed your headgasket and the last one blew there could be a little bit of coolant under the oil cap as thats what ive seen happen to peoples and my cars in the past

 

[viprez586]

well if you just recently changed your headgasket and the last one blew there could be a little bit of coolant under the oil cap as thats what ive seen happen to peoples and my cars in the past

Moisture or yellow/white muck under the oil cap is completely normal unless you pulling out gobs by the hand full. Moisture seeps into the engine overnight/ morning dew. Most of it is burned up but whatever remains tries to escape with heat(rising) and collects oil particulate with it in its ascent, it usually forms on the dipstick and oil cap.

Anyway the OP already stated he sees oil in the #3 cylinder.

Imagine that, my cylinder 3 was filled with coolant when my HG blew.

 

[GooeyGus]

It was the headgasket. I changed it a few days ago and it's all fixed.

One of the SUPER tiny coolant passages, on the front of the block between cylinder 2&3 was leaking.

It was almost like the "filling" of the headgasket had worn away in that spot, so you could see the crosshatch of the base material of the gasket. This was enough to allow coolant to seep into #3 while the car was off (and coolant system pressurized) yet allow the car to maintain good compression as well as keep the coolant out of the combustion chamber while the car was running.

It gave me an excuse to put on all new timing components (WHICH BTW was a piece of cake... I had the tool kit from Jay racing and it took me less than a half hour. I expected much worse from everything I've read) as well as ARP head studs and a new OEM HG.

In total, the car was only down for 4 days, not bad! Confirmed the problem wednesday after work, parked it until the weekend, pulled the head and put the new head on on saturday, re-assembled everything else and fired her up sunday night.

 

[white92talontsi]

This Is a very common problem on alot of the Newer Nissan Sentras with the 1.8. They will only leak with the engine off and the coolant system pressurized. The misfire badly on first start and then clear up and dont leak while running.

Glad you got it fixed!