My 1600 may have a blown head gasket?

[Datrock]

Yes, I will be putting a new thermostat in the engine before it hits the road. Right now I'm just trying to get it movable on it's own power so I don't have to push it back and forth. The engine will probably not even get close to its operating temperature, so no harm done.. Bill

[dbrick]

The Z engine builder we got the info from was Bob Sharp Racing, he reccomended the article by Smokey Yunick. Rules of thumb exist because they are generally correct or at least a starting point.
Being air cooled, thermostats are considered purley optional on garden tractors.

[toolsnob]

I have had a couple motors (not Datsuns because they are tooooo reliable) with blown head gaskets/manifold gaskets. And in each case I experienced a loss in coolant from running the engine. Generally the exhaust was pressurizing the coolant system and forcing coolant out of the weakest spot, like a heater hose or over flow tank, other times it was burning the coolant and you could smell a sweat smell coming from the exhaust.

I forgot, my 69 had a bad head gasket! That was my first datsun project. It was having cooling issues and overheating. I had the radiator rodded and checked everything and still had the same issues. Turned out it needed a head gasket and the head cut.

I have never compression checked a motor with a leaking head gasket, just after so I don't know if pressure testing will give you a correct reading. I would think that the car would let coolant in causing it to burn which wouldn't affect compression....Am I wrong?

[dbrick]

You can test it in reverse too, remove the plugs and pressurize the cooling system. If it won't hold pressure see where the green stuff flows out. Small leaks take a while as 15 or 20 psi on the coolant is alot less than compression/combustion pressure. If the radiator is old, go easy on the pressure.

I had a Saab someone gave me with such a bad head gasket leak it was blowing liquid coolant out the exhaust. The woman was filling it up every morning and driving a couple miles to work for months!!! It started up and blew a 10 foot spray of coolant out the tailpipe. Mufflers filled up with coolant after the engine shut off. Changed the gasket and I put 20,000 miles on it and sold it still running. That one was kinda easy to diagnose.

[ambradley]

I know I'm late to this thread, but if your car is truly overheating immediately, you're probably looking at a head gasket leak into the water passages. When I had this problem, it sent hot gasses into the coolant, pressurizing it and turning the overflow tank's lid into an air horn.

[Datrock]

Hi Adam, The overheating went away with removing the thermostat for a temporary fix. I had some of the same symptoms as you mentioned, hot gasses coming up thru the overflow tank. To me it seems like the engine coolant flow was blocked, thus allowing the coolant in the block to boil over, Hopefully between a new thermostat and getting the air pockets out of the system it will be fine. If not it will be headgasket time.

I know I should have pulled the head before testing the motor, but it only needed the intake bolted down and gas and battery and it fired up. I know nothing about the history of the engine so I feel lucky that it is not knocking or smoking.

Right now I've moved on to the rear axles, which I found out last night that they have been drilled out for 12 mm studs by PO. So I'll be doing some axle switching. When I got the car one of the axles was broke at the hub. The super glued 7/16 studs that were loosely fit in the hubs may have had something to do with busting the axle. Thanks for your input.. Bill

[itsa68]

Can anyone scan and post the troubleshooting page 35 of the 1961-1972 Chiltons Datsun Repair and Tune up Guide book?(The purple book with the 240z on the cover) There is a test procedure for the problem.

I recall seeing someone diagnose combustion leaks into the cooling system using a radiator pressure tester as shown in the book.

The tester hooks up to the rad cap hole (to overflow bottle or filler on 1600) and the pressure guage needle flutuates if there is a leak.

Hope this helps

Ray B.

[Datrock]

I've also been told that the radiator shops use a carbon monoxide or dioxide sensor that will detect exhaust leaks into the cooling system. Does anyone know if they charge for detecting leaks?
Last year a person from the gas company was out checking the neiborhood for any line leaks. We were talking cars so I started the roadster up and all of a sudden an alarm on his sensor tool started beeping because of the exhaust out the pipe. Bill

[Russell Roach]

Dave,

Wasn't Smokey's hot vapor engine only a two cylinder, absolutely love the man and his work. I know that His Indy cars had a different number of cyliders.

Another Disciple of Smokey

It didn't say you couldn't

Russell

[dbrick]

I think he finally scaled it up to a VW rabbit engine. There was a special about him, Maybe on Speedvision or History channel, was really good.