Head Gasket Leak?

[ShelbyLancer#771]

Finally had a chance to take my S/L for a good drive today. Problem is when I got home the coolant boiled into the overflow tank but when it cool down it went back into the rad. I'm I looking at simply a weak rad cap or is this a tell tail sign of a head gasket going out? No white smoke out the tail pipe. No oil in water or water in oil. Thanks for your input!

[Tony Hanna]

Finally had a chance to take my S/L for a good drive today. Problem is when I got home the coolant boiled into the overflow tank but when it cool down it went back into the rad. I'm I looking at simply a weak rad cap or is this a tell tail sign of a head gasket going out? No white smoke out the tail pipe. No oil in water or water in oil. Thanks for your input!

From past experience, when the headgasket goes, the coolant will get pushed into the reservoir as the engine heats up, but won't draw back into the radiator after it cools down. Instead, it will draw air into the cooling system at the bad spot in the headgasket.
A telltale sign is a constantly full or overfull reservoir while constantly having to add some coolant to the radiator.
Pull your radiator cap off (cold engine) and check the coolant level in the radiator. If it's full up to the cap, then I'm guessing your problem comes from something other than the headgasket. Cap or thermostat possibly.

[ShelbyLancer#771]

Yup, radiator is full to the cap when cold. Hmmm I didn't think about the thermostat. Thanks:thumb:

[Tony Hanna]

Yup, radiator is full to the cap when cold. Hmmm I didn't think about the thermostat. Thanks:thumb:

You're welcome.:thumb:
Just keep in mind if you remove the thermostat to inspect/replace it, you might have to fight with it for a little while to get all the air bled out when you refill. Some are more of a problem than others. My old Daytona would take an hour or longer of idling with the cap off and adding coolant as the air made it's way out. For some reason the Sundance I have now only takes a few minutes. You'll know when you get there as you'll stop seeing air bubbles coming up in the fill neck, and the heater and temp gauge will act normal. Any large ammount of air left in the system will cause the heater to alternate between hot/cold depending on engine rpm and the temp gauge will act screwy.
Good luck with it :)

[Birddog]

To help with bleeding the air go to a supply house and grab a key vent for a home radiator. Swap it in place of the "allen" plug on the head before the stat.
Makes life a lot easier!

[racer-xerols]

...or just drill a hole in the top part of the thermostat - turns a 180 into a 160, and "self-bleeds". I think the hole's a 1/16? Or is it 1/8?

[Tony Hanna]

...or just drill a hole in the top part of the thermostat - turns a 180 into a 160, and "self-bleeds". I think the hole's a 1/16? Or is it 1/8?

The Daytona would take an hour or better to get all the air out with the hole in the thermostat. It was worse without it.

[racer-xerols]

Odd. Every car I've had with a drilled thermostat (and you have to make sure to install it with the hole at 12 o'clock) took one heat cycle to bleed the air out. No temp gauge spike, no extra care required.

[tryingbe]

Replace the radiator cap.

[ShelbyLancer#771]

Yup, You beat me to the post LOL. I think that did it:thumb: Thanks for all the help eveyone!