A good screw cleaning always helps...

I considered that, but actually I was trying to make sure there was no possibility of the leak originating from the lines or the threaded fitting for the heater core lines, a much simpler problem.

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-Chris

i found out the leak while retorquing bolts.. its head gasket after loosening bolt number 11 (wich is one over starter) it started to drip water from the rear and the bolt hole filled with coolant.. i'll do the final torquing but i dont think it'll help. Blaah..

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240zgoldie.blogspot.com

If the bolt hole is filled with coolant, you probably won't be able to reach final torque. Fluids don't compress.



You might have to drain the coolant out, soak the coolant out of the bolt hole (capillary action works), re-torque the bolts, then refill the system.

BTW, have you done a recent compression check, to zee if the rear cylinders are the same as the others? If they are, you might (might) get away with just tightening the head to seal the leak. If they are significantly lower than the other 4 cylinders, you have a blown gasket and will eventually pump coolant into the cylinders. Compare the sparkplugs, as well, to zee if the rear two look different from the others.

FINALLY, if the gasket isn't blown and you don't want to pull the head unless necessary, you could (could) try a very hi-quality system leak sealer. I usually don't recommend them, since they can (if over used) gum up the water pump. But if you only use one can it probably won't hurt the car, and might (might) seal the leak after you've re-torqued everything. If it doesn't work, well, you had to drain the system anyway, to pull the head.

Other members surely have experiences with radiator sealer /coolant system Stop Leak. It has worked for me in past years. Their opinions are solicited.

Frank

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1970 240Z

I do have made compression tests and all the cylinders hit 150. That suppose to be good AFAIK. Gasket seems to leak only out of the head and inside the bolt hole. Also the rear 2 spark plugs look like the others, normal.

Now i wish i lived there, you guys are so much more helpful than the local dudes here.

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240zgoldie.blogspot.com

Well, we wish you lived here, too. We could zee your Z more often!

The good thing is that your compression is excellent. 150-160 is exactly what you should hope for. It's more important that they are all alike, than that they have high numbers.

OK ~ so your gasket isn't blown, it's just leaking. Simple stuff.

I would recommend draining the coolant level below the bolt hole (or just take it all out and refill it later), then extract all the coolant from the bolt hole. I would use an old T-shirt and a straightened coat hanger. Push one end of a shred down into the hole and let it soak up the coolant. Continue that until you can push a shred all the way to the bottom of the hole and it comes out dry. Blow air down in the hole if you have a compressor ~ that will save you a lot of time with the T-shirt.

Then retighten the bolts according to the FSM tightening sequence.

Then replace the coolant. If that doesn't stop the leak, you still have to pull the head and change the gasket.

*When you refill a completely dry cooling system, remember the thermostat must be allowed to open before the system can be completely refilled. (When you fill a cold block, the thermostat is closed. Coolant enters the block from the bottom radiator hose, so it RISES inside the block. But the cold thermostat at the top of the head is a closed door, which will not allow coolant or air to leave the block. So the rising coolant tries to compress the air in the head, and you end up with an airpocket instead of coolant under the thermostat, and the upper radiator hose is empty. The radiator will be full, so you think the engine is, too. But it's actually missing about a gallon of coolant inside the head.

Leave the radiator cap off, and run the engine at an idle. After a few minutes the airpocket in the head will heat up enough to open the thermostat, releasing the trapped, pressurized air thru the upper radiator hose into the radiator. Your temperature gauge may show some scary temps before this happens.

It sprays and bubbles over and gurgles and splashes steam and hot coolant all over the car, the garage and you, if you're standing close. Then the coolant level in the radiator will drop to the level in the block, and you'll be able to SLOWLY pour in the remainder of the coolant to fill the radiator again. This time the entire system will be full). If you put that old t-shirt over the open radiator hole, it will stop the hot steamy coolant from scalding everyone when it surges and splashes out.

Anybody have a better plan?

Frank

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1970 240Z

Thanks for the hints Frankie. I think i need to change the gasket anyhow. I cant do it this weekend, as i we have graduation weekend and i must attend to my cousins graduation. Also Z has a photoshoot next tuesday.. BUT can any of you kind gentlemens write a step-by-step instructions for head gasket change so i can use it as a manual?

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240zgoldie.blogspot.com

You can download a free complete factory service manual for the car at :
http://www.xenons30.com/reference.html.
For simplified, photographed, thorough instructions, I highly recommend:
http://www.amazon.com/Rebuild-Your-Niss ... 175&sr=1-1

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71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it

I suggest a new gasket, sounds gone to me.

i do have FSM. Just wondering if any of you guys who have done it in your 240z, could share your wisdom to the world

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240zgoldie.blogspot.com

It's really a pretty simple job, take it apart, assembly is opposite of diss assembly. There are only two hazards to the job: make darn sure you have the timing chain tensioner wedged properly before you take the cam sprocket off, and some people miss the two bolts in front that go into the timing cover. The biggest part of the job is getting the carbs and exhaust out of the way. It is possible to do the job without removing the manifolds, but remember to order a new manifold gasket (one gasket for intake AND exhaust manifolds) if you decide to take them off. Finally, of course mark your timing chain and cam sprockets before you take it apart so you will be sure you have the timing right when you put it back together.
There is more than one way to do this job. You can leave the manifolds on but reassembly is tough. You can take the manifolds off with the head still on the motor, but the bolts are hard to reach. Personally I prefer to disconnect the fuel lines and the exhaust, and remove the entire head including carburetors and exhaust manifold with a hoist. Once I have the head out, I can easily get to all the bolts and then I remove the manifolds, clean everything up, and replace the manifold studs with new ones. Then I install the new head gasket and head, and finally install the manifolds back on. I do it this way because I find that it is much easier to make sure that the head gasket and mating surfaces are all perfectly aligned and clean when the manifolds are off, and installing the manifolds when everything is clean and new is pretty easy.
Of course, you can leave the manifolds on throughout the entire job if you like, or you can take them off before you pull the head, which you might want to do if you don't have a hoist. To be honest, it's not a huge difference whichever way you choose, but I have done it several different ways and in the end I prefer to pull it all in one big assembly but put it back together in small pieces....

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71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it

When ever I remove a head, I ALWAYS take it to the machine shop and have it milled and cleaned, and if it was a steam producing machine, ALWAYS have it pressure checked, (magna fluxed for cast iron). So it requires you to remove manifolds and valve train. Not a big deal on a 240.

Do you leave valves and stuff on? I dont want to mess with them.

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240zgoldie.blogspot.com

Yeah, no need to remove them unless they are obviously broken, burned, chipped or bent. If you have good compression in each cylinder, they're OK for now.

Many owners use such an opportunity to have the head reworked, since it's off anyway. But if you're concerned about budgets and down-time (when you should be driving), it's HARD to delay your Z road-time during good weather, waiting for a shop to work your cylinder head!

It's a few hours' work if you're alone. More funner if you have a bud helping you.

Start by taking photos all around, to answer any "how did this go on?" questions later. New hardware (nuts/bolts/washers/capscrews) will make the job lots more fun.

Frank

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1970 240Z

If your going to have them hot tanked, it's a good Idea to strip the head. just keep everything in order, and now you can replace the valve seals as well, and have the guides checked. It's alot easier then the Acura I just just did, 2 heads, each with 12 valves and a very delicate valve train as well, lots of parts. Also, if you're going all the way with this, then I would get the new head bolts as well. ARP studs even better.