Disappearing Coolant

[Tonymig]

[*]hi everyone I have a 69 3112000 I am losing radiator fluid and no leaks detected. Any thoughts? I get blue gray smoke exhaust when first starting with choke then clear once choke is off. I do get what I believe is excess water vapor from exhaust especially when first started then it stops once at temperature. The car runs extremely cool at maybe 150 -160 any thoughts?

[Gregs672000]

Sound like a blown head gasket. A compression test may tell you, but there are specific tests you can do to detect exhaust in your coolant. Check with your local parts store, they can probably guide you and set you up. After that, we can discuss your options for repair. The only two places to lose coolant are the head gasket or sometimes the intake gasket. If you smell the exhaust, it will have a particular smell, but it won't tell you where it's coming from, and that's why the specific tests help identify the culprit. Check around the underside of the intake manifold with an inspection mirror to see if you see any signs of leaking there, as there is a water passage there that can leak (search recent posts on that issue).

[Tonymig]

Thanks for the input!

[redroadster]

Does the cooling system hold pressure ...with a pressure tester ? Bet its worse if you seal it up
I've been limping around a 96 monte C with the same conditions about a qt. In 2-3 weeks
Coolant burns white and disappears
Pull the plugs and after it sets hours watch the clys as it cranks over

[mraitch]

Apart from a 'compression' test, there is also a 'leakdown' test. This test fills the cylinder with compressed air and then measures how long it takes to drop. IMHO better test for potential head gasket leaks since typically they are tested for about 20-30 rpm.

[Tonymig]

Does anyone know Where’s the best place to get a radiator pressure tester that fits a Datsun ?

[Linda]

Autozone has loaner tools for free with a deposit. I think they have that one plus an exhaust gas tester . Check their website or go in and they can show you.
Linda

[The Neck]

This is what I bought. I've used this tool more than almost any others in my garage as I'm constantly removing hoses, and was having coolant issues for a while. Also a block leak test is a very good thing to have in case you're having an exhaust leak INTO the coolant which I did. I've also found if I fill the expansion tank and attach the pressure tester to it, I can use that to bleed the system.

https://www.amazon.com/12270-sistema-re ... ive&sr=1-2

[spyder]

Pull the plugs and see if one is super clean.

[Tonymig]

Spyder. What does a clean plug mean? Aren’t all plugs suppose to light grey clean?

[Gregs672000]

It will appear different, even white and clean vs the other plugs due to burning coolant in that cylinder.

[Tonymig]

Well I did a compression test . each cylinder Read from 125 to 135 also did a coolant pressure test. Pumped it up to 20 lbs did not see and leaks. Left it hooked up over night and it dropped to 12lbs . Do these readings tell anything to anyone? Still lose coolant but temp never rises above 150

[Gregs672000]

Unless you're finding a fouled spark plug, I think I'd run it and see what happens.

[mraitch]

125-135 seems low!!

[redroadster]

Coolant stop leak is an option
I saw a few Datsuns that had putting thru the cly walls from sitting around for years with no coolant