Head gasket fairure??

[z.Leinbach]

Well I'm almost certain of a head gasket failure on the drive bank, as I have bubbles in the coolant, did a block test and it turned a teal colour with the quickness, I have 2 cylinders with the next to the same compression and the 3rd with low compression (125ish), granted the car will still pull against one of its own, and the whole of the passenger bank tested at 186 no difference between them

1+ everytime that I have changed the oil, (more then I should but oh wellz) I haven't noticed any milky appearance or metal shavings. Went of a road trip of a total of 8 running hours non stop except for fuel up.

Well as the trip went only had to add a touch of coolant less then half a cup (for safeness) before the home journey, seafoam was added to help clean(buddy got it for his car as a precaution as well.) Tuesday rolls around an I notice some untouched oil at work with cobs on it, ask what up with it, parts say don't know take it, so get home state work change the oil and niiice super dark gold oil, no shavings filings or milky mostly common of head gasket failures, but as I filled up the recycle bucket, I noticed moderate sized chunks of carbon.. this normal for our cars?? An could it be the cause of such low compression??

[budget300zx]

try doing the seafoam intake treatment. ive found it works pretty well with large carbon buildup on higher mileage cars.

good reference video


what it does

[z.Leinbach]

I heard seafoam wasn't that effective on our cars due to the dual throttle body set up, but I have done the Wynn's fuel system cleaning, along with some pour in the tank cleaners.

[budget300zx]

just use a Y and use the 2 throttle body vacuum lines. may free up carbon from your piston and rings and possibly some intake valves depending on how they close. the pour in gas method is very ineffective. that method works well for injectors but not much else unless used for long periods of time.

diagnosing much more would require break down of the engine, or wet compression tests with higher readings.

possibly you have soft valves, head gasket failure, bad rings, burnt valves, ect.


soft valves on 1990 models (not likely but possible)
http://www.twinturbo.net/nissan/300zx/f ... alves.html

[z.Leinbach]

I'm almost certain it's a head gasket and valve train problem, cause almost everytime I shut it down there is rattling coming from that side of the engine, so I am kind of set on doing some performance aimed upgrades, cams(want a lope and more aggressive power band), gears, springs(stiffer to avoid float), valves(not certain what to get there), and underdrive pulleys as well even though it gets hot here in the summer