A nissan 720 followed me home and dropped it's problems at my door!

[jagman]

I have driven the truck for a month and last week she overheated miles away from home.  I  got her back by filling the radiator time and again but after replacing the (a) bypass hose and refilling the cooling system she now blows white smoke at idle. Definitely  antifreeze.  I have not worked on  a Z24 engine and need help in understanding my  options  for fixing this problem at minimal cost. In addition, I would like to eliminate some of the spagetti vacuum lines if I can when I tear it apart just to make  life easier later.  All the help I can get is appreciated. She is an '85 long bed in decent shape.

Thank you, Jagman

[datzenmike]

The Z24 is known to blow head gaskets every 100K. It probably blew causing the over heating. Nothing you can do now but replace the head gasket. Over heating can cause the head to warp so lets hope that is not the case so far. If you do the work yourself, this will cost you about $25 for the gasket.

 

MAKE SURE YOU SECURE THE TIMING CHAIN PROPERLY BEFORE REMOVING THE CAM SPROCKET, OR THE CHAIN TENSIONER WILL FALL OUT, ADDING SEVERAL MORE HOURS OF WORK AND MORE GASKETS. AVOID THIS AT ALL COSTS.

 

Disconnect the battery.

Drain coolant.

Disconnect the EGR pipe from the intake manifold. Unbolt the exhaust manifold from the head and hang to the side. EGR pipe will stay behind head out of the way.

To save time, and another gasket, the head will be removed with the intake and carb attached. So get some help for lifting it off.

Disconnect the block vent pipe that also goes behind the head to the PCV valve on the intake. This will stay sitting behind the head.

Disconnect the fuel lines, battery cable, unplug the wires to the carb and the throttle cable, Take distributor cap and wires off so it doesn't get broken, any vacuum lines and hoses coming from the intake. There is a small bolt holding the metal block vent pipe to the right rear of the head, heater hoses. Anything that will prevent the head being lifted off needs to be disconnected. Use a camera and take lots of pictures so you know where everything goes that was removed. 

Loosen but DON'T remove the cam sprocket.

Mark the chain and the sprocket so it goes back together the same.

Set engine to TDC

Secure the timing chain tensioner with the wedge. Find out how to make one or buy one on Amazon.

Now remove cam sprocket and loosen/remove all head bolts. Do NOT turn the cam once the head is off.

Lift away the head but try to keep level so any sediment in the carb is not disturbed.

 

Clean block surface, same as the head but be careful the aluminum is much softer. You can't get them too clean but get as clean as you can. You can tip the head up to get at it but don't move it around excessively.

 

Head bolts are reusable if clean and undamaged.

 

Torque the bolts in three stages with a torque wrench starting in the middle and working outward...

R A D

8....7

4....3

2....1

6....5

10..9

 

Tighten in the order to 20 ft lbs, re-tighten in this order to 40 ft lbs and finally in this order to 60 ft lbs. Once a year, on a cold engine, loosen each bolt ONE AT A TIME and tighten to 60 ft. lbs. but only one bolt at a time is to be loose.  This will prevent blowing the gasket again.

 

Assemble.

 

 

 

[jagman]

Thank you for your advice.  I will do my best to follow your instructions but am curious as to how to handle the warp problem if it should be present.  I am led to believe that I would have to disassemble the valve stuff to have it milled flat.  If that should be the case,  I will need more advice.  Sorry to be such a pain in the tookus.  The expertise on this forum is fantastic and fast!

[datzenmike]

It's much easier to remove the intake from the head when it's out of the truck. The head can be checked for warp with the straight edge and feeler gauges. You will need something accurate and flat for this. Check diagonally in an X pattern and lengthwise where the cylinders are closest. If you can slip a 0.005" feeler gauge under the straight edge anywhere, it needs to be planed. Five thousandths is about the thickness of a Post-It note and on most engines I wouldn't care but the Z24 is known for blowing gaskets so I wouldn't give it any excuse.

 

This may not be a problem anyway.

[jagman]

I  have removed the  power steering belt and the unit and  the air  plenum and am finding a  lot of what appears to be vacuum tubing going everywhere.  Can some of these be eliminated when I reassemble the engine.  Some of it goes to what looks like little cans on the passenger side and one goes to a round thing on the side of the engine that is held in place with a metal band.  Is all of this for emissions?  I have lost the timing chain even with using the recommended wedge. Turns out that the right side timing chain blade was bent away from the block to the front so the wedge had nothing to solidly rest against.  I have removed all of the bolts holding the timing chain cover on and find it solidly glued to the block!  I have used brass drifts to try to budge it to no avail.  What else might work?  A friend came by and was looking at the truck and proceeded to split it from the block. Magic I guess!  Someone put it on with glue and it wouldn't budge for me.  All is well for now....

Edited October 3, 2018 by jagman
Just a little aggravation