Leak from headgasket

[blueghost510]

I picked up a 620 and noticed that there is a puddle under the truck after it has been run and warmed up. After nosing around under the hood, I was able to find the source of the leak. It's coming from the head gasket just below the exhaust manifold. I've had a few head gaskets go over the years in various datsuns... but never leak out (it's always into the cylinder). Wondering if anybody has had this problem before. Am wondering if I should get in there and check/tighten headbolts.... or is a new headgasket in order?
Truck doesn't overheat, idles great, and there is no smoke in the exhaust.

[wayno]

I picked up a 620 and noticed that there is a puddle under the truck after it has been run and warmed up. After nosing around under the hood, I was able to find the source of the leak. It's coming from the head gasket just below the exhaust manifold. I've had a few head gaskets go over the years in various datsuns... but never leak out (it's always into the cylinder). Wondering if anybody has had this problem before. Am wondering if I should get in there and check/tighten headbolts.... or is a new headgasket in order?
Truck doesn't overheat, idles great, and there is no smoke in the exhaust.

I have had this happen before, it was because the front driverside headbolt threads stripped out in the block near the thermostat housing, so I could not torque it anymore, it would just spin.

[blueghost510]

Don't say that. HAHA

It crossed my mind that could be a problem, but am a glass is half full kind of guy! Tomorrow I'll get in there and torque on them and see. Were you able to come up with a fix for that? Thanks, Ryan

[wayno]

Don't say that. HAHA

It crossed my mind that could be a problem, but am a glass is half full kind of guy! Tomorrow I'll get in there and torque on them and see. Were you able to come up with a fix for that? Thanks, Ryan

I had to remove the engine and take it to a machine shop to have a heli-coil put in it, it was a fresh LZ23, so I had to do it.
When I put it back together, I used a L block stud kit from ARP, not an issue since.

[Laecaon]

I have heli-coiled my block outside of the car successfully, and my friends block in car successfully. The kit comes with the proper drill bit, and tap. Take your time, and tape over the cylinders/water jackets before drilling/tapping.

But yes try retorqueing.

My engine was leaking on the passenger side when I first assembled it, but it went away 3 months later (2 retorques)

[blueghost510]

I was just looking into the heli-coil kit, and the possibility of doing it myself. Doesn't sound too difficult, just time consuming. Thanks for the warning... yeah it would make sense to tape EVERYTHING off aside from the work area.

[wayno]

I was just looking into the heli-coil kit, and the possibility of doing it myself. Doesn't sound too difficult, just time consuming. Thanks for the warning... yeah it would make sense to tape EVERYTHING off aside from the work area.

Maybe you don't have stripped threads, you cannot tell till you pull it apart, finding a headbolt loose when you start taking it apart is a sign though.

[izzo]

You sure it's not coming out of the valve cover and running down? Or from the front of the motor streaming back from driving... then going down and puddling up on the ground?

[datsunmike]

OK ... if it's on the driver's side it can't be oil as the oil feed hole up from the block into the head is on the right side. At least it can't be the head gasket.

If it is oil, it's the valve cover gasket or the block vent tube not seated tight into the block.

If coolant (I wish you had said what was leaking) and your 620 is not a '75-'77 then it's likely the intake coolant leaking from a bad or loose intake/exhaust gasket. You might be able to tighten the studs but be careful. If you have a header this is almost certainly the cause.

[blueghost510]

Izzo... that sounds a lot like the magic bullet that killed Kennedy:) I'm positive it's leaking from the driver side head gasket area.

I'm 100% sure it is NOT oil. It is Anti freeze.

Mike it's a stock exhaust manifold, and there is a "ticking" coming from the exhaust manifold. With the truck running, I put my hand under there and could feel the exhaust coming out.

[Laecaon]

Heat rise intake/exhaust?

[blueghost510]

"Heat rise intake/exhaust?" Not sure what you are asking.

[blueghost510]

Oh and thank you all for responding. Your input is appreciated.

[Laecaon]

Are the intake and exhuast connected or separate?

What year is the truck?

[blueghost510]

My truck is a 79. They are separate.

[Laecaon]

So coolant could be draining from the intake manifold then. Every head except for the U67, has coolant ports to the intake manifold. Its common for this to leak.

[blueghost510]

Perhaps this is a combination of two problems then? A leak at the exhaust manifold gasket (which is audible), and at the intake with anti freeze leaking down the side of the block?

[izzo]

possibly. Are you sure your manifolds are seperate? not that it matters tooo much. But just curious. If stock then they are a pain in the ass. if someones replaced them, it'll be a lot easier to pull them and clean the surfaces, put a new intake/exhaust gasket on. Could always do what Jacob was talking about. And re-torque the head bolts. just be sure and do 1 at a time. 20lbs, to 40lbs, then to 60lbs. In steps.

[datsunmike]

Ah a '79... then the intake/exhaust gasket is the most likely.

[blueghost510]

Good deal. I already ordered one of those today. Figured at the VERY least the exhaust was coming off anyway. Going to make sure the bolts are snug tomorrow and see what happens. Glad I asked on here first. Was getting ready to tackle a head gasket!