Changing head gasket on 720D

[chas036]

I have a 720D with a pony motor that has been sitting in my barn for 18 years without starting. Last summer after some small repairs like changing the diesel water pump because of leaks, and the thermostat, and putting new coils and plugs in the pony, I got it started and it seems to run good. The one problem that I have now is that it builds so much pressure in the radiator, I loose about a gallon of water out the overflow every time I run it. The thermostat is working good because I see the temp gage get to 180 then hold steady. From what I read this pressure build up in the cooling system is probably froma leaky head gasket, so I have plans to change it here soon as the waerther warms up.

My question is, can you tell what are some things I shoudld be aware of when doing this or things to look out for?

I have the shop manual that tells how to change it, but I know that when you actuallly do it, there are things you see and learn that are not in the shop manual. I have changed head gaskets before on a 60 and 620, but never have worked on a diesel. Can anyone give me some hints from their past experiences? Also, can I remove the head without removing the fuel tank?

 

[David G]

Does it keep losing after the gallon, or stop?

 

[bill finn]

head gaskets can fail due to a poor cooling system. This will allow the engine to run hot and eventually warp the head and blow the gasket. When repairing a head gasket leak, find out why it failed. Example, radiator internally corroded restricting water flow, external material restricting air flow, ran with low water(leaking water pump). good luck with your project

 

[David G]

I was wondering if the radiator overflowed because it was overfull, does not seem probable, the expansion of water is about 8% from 60 - 180 degrees, so that would mean it would not weep more than about quart and half.

 

[jdjerry]

I fill my 70D about a 1/2 inch over the top of the core and it stays there. If I fill it to the filler neck it pushes it out the overflow. My gas two cylinders are filled the same way.

 

[Mike M]

Last one I did the gasket set came with copper washers for the studs instead of the lead washers. DO NOT use the copper ones ! Get the lead ones. Copper will not squish out correctly as it is too hard, but is still too soft to hold the torque right.
I also used some sort of aviation gasket maker to seal around the ports and the cyl. area of the head gasket. I think it was Clooney that used this on head gaskets ? I have gotten away from copper coat as I was not pleased with the results sometimes.
Retorque it after warming it up. Always good to send the pumps and injectors out to get checked over too.
Been running into a few injector lines that after being taken off and reinstalled end up developing cracks later and need replaced. Old age metal fatigue is surly a factor too. If there is money in the budget may be worth replacing them ? now instead of later down the line.

 

[RLA]

Does it leak down below the core? Many will find their level & spit some out. Do you smell antifreeze
out the exhaust after you first start it up? If the head gasket is leaking & after it's been run for awhile
you should see evidence of coolant coming out the exhaust at start up.

 

[DONMYEIL]

When you get the head off have it Magna-fluxed for cracks. Check the nozzle bores also. Have the head resurfaced . We only used high temp aluminum paint ,put the head back on the studs and then paint all surfaces gasket as well , then tighten it down right away while paint is wet, starting in the middle working out to a final torque of 275-280 ft.lbs. if memory serves . Definitely use the lead washers .