dorcom

Hello all!

I Rrunner V6 with somewhat relative low mileage for the age 155,500.
I bought it as a daily beater to replace my dying '86 Landcruiser with 360k miles. (Needs a ring job badly!)

Shortly after the purchase of the 4R I ended up with coolant in cylinder 1 and when running the typical "steam" coming out of the tail pipe.
F* S*! I know what that meant: head gasket.
Though I did a check prior to the purchase and found the recall was done, I got hit with a leaky headgasket again! Bubbling coolant on a cold engine and a couple of almost hydrolocks during start confirmed all.

Fortunately, a combination of first using "Blue Devil" and then "K&W Nano fiber" head gasket fix did the job amazingly 100% ! YAY!
You do have to reverse flush the radiator after the K&W as it clogs it gradually up.

I have driven so far a couple of thousand of miles and all seems well.
What puzzles me is that although the cooling system holds the pressure 100% there seems to be a bizarre reverse mystery leak when cooling off. It sucks air from somewhere thus does not pull the water back in from the expansion canister (all checked).
There are no leakage drops anywhere, neither into the engine oil or transmission or elsewhere.
How can this leak suck air only in "reverse" when contracting during cooling down?

Another thing that surprises me is that engine temp is stable.
Due to the additives I had removed the thermostat yet it seems to have no effect.
The engine seems to warm up normally to operating temp in about 10 - 15 minutes and stays stable throughout all driving conditions.
I drove on a 100° F day with A/C full blast up a mountain with stable coolant temp readings of about 180º - 195° F throughout.

BUT then there is SMOG check:
I'm in California and I didn't pass smog though all was pretty good, the NOx was way to high (3x the maxand the CAT was a "rescinded" aftermarket one.
I know High NOx is related to EGR malfunction and/or a bad CAT but also to lean mixture.
The EGR works but I did find the modulator function was questionable and replaced the modulator with an OEM new one. Tomorrow the new CAT (made sure it's a CA C.A.R.B. approved type) goes in and I hope very much I pass smog!

Issues I have:
Currently, my check engine light comes on after about an hours of driving but goes off again after a couple of hours only to come on again the next day after an hour or so driving.
I have reset the ECU and the phenomenon appears again as described above.
I have yet to bridge T1 E1 to see the code blinking sequence.
My worry is if it comes on during smog check....

What you say to all this?
Any expertise or good knowledge replies are very much appreciated and I thank you in advance!

oldblue

you're gonna wish you hadn't put any form of "fix a leak" in your truck. though it works, i've seen it fix many a car, it wreaks havoc later. i did a head job on a buddies civic after he used that crap. his thermostat was completly plugged, and that blue devil had coated the outsides of the cylinders with this crystalized ˟˟˟˟. i'm sure that doesn't help with heat dissapation.

a new converter should help with your nox situation. those aftermarket converters are crap and will only last a year or two. i've been through several trying to smog my truck.

Qbert

Fix a leak is another name for 3VZE killer. I put some in for a quick fix on a leak to get me by till payday. BAM! 2 days later blown head gasket.

scope103

Do it now; you've almost certainly got a stored code. Your engine is trying to tell you that something is wrong; would you rather pay $59.95 and find out the same thing that way? And as you point out, if it comes on during the smog check (you know it will), you'll fail immediately.