Joshlwd

My F150 has the 4.6. Early last week the temp gauge went hot. I pulled over, let it cool and stopped at a repair shop I know well. The coolant level was dangerously low (I had been smelling coolant, but have never found any puddles, leaks, etc.). The mechanic topped off the coolant and told me to keep an eye on it.
It's been a week and the check engine light came on today. The coolant is very low again. I borrowed my dad's OBDII scanner and got a code P1299. I still don't see any visible leaks, puddles or anything.
Has anyone had a similar issue. The truck runs good but I still smell coolant inside. The floor is dry too.
I'm wondering if it might be the intake plenum. Any suggestions would be great. Thanks

Jbrew

Shine a flashlight down in the block behind the alternator. Is the valley full of coolant?

redfred

Check your oil to see if its got in your engine. if it has the oil will have a milky white color.

capri debris

Disappearing coolant with no visible leaks can only mean it's being consumed in the combustion chamber.... which means a blown head gasket or manifold problem. So unless you can find an external coolant leak, the intake and/or heads have to come off.

Jbrew

Yea, he said he's been smelling coolant, but not exactly where....

akdoggie

I have to sort of agree with the fact that it is most likely combustion chamber related. Probably it is a head gasket separating at the water jacket, giving you the antifreeze smell. I hope I'm wrong, but it is either that or a broken (cracked/damaged) intake plenum. Good luck

TheUnforgiven71

You can rent a combustion test tool n fluid from your local autozone to confirm if it's a blown head gasket, another thing it could be is the heater core I had mine go out on me about 2yrs ago you would smell it and see slight smoke/vapor from your ac vents, I didn't notice any fluid in the truck when mine gave out

biglee88

Might be the heater core since u can smell it inside. Y didn't the shop pressure test it?

biglee88

Oh and my super duty cracked the tank at the very top it wouldn't leak untill the coolant got hot and the plastic evpanded. But it would only loose about a gallon and no more maybe a situation like that.

95ford5.0

Get ready. Check you oil ASAP. If it's turning milky then your engine needs a rebuild. Seals or gaskets are bad somewhere.