Coolant issues

[Karenvinn]

I know you read this problem a few times but I done everything suggestion.
99 ranger 3.0 flex fuel.
My coolant gauge goes up and down and the heat goes cold to hot. after driving it it all goes to normal. This mainly happens in the morning and now started to happen more frequently. I replaced the t Stat 4 times and I used an airlift system to fill the system. After appling the vac it held for 20 min (I think would tell me if the head gasket was blown.) filled it up and get the same results. The coolant would go over to the overflow tank and blow the top off of it. I did change out the radiator cap as well. I notice at one point my top hose was fully collapes then it went to pulsating. I read a lot saying head gasket but wouldn't it loose vac on the airlift system if the gasket kit was leaking. I know a system leak down through the plug hole is recommended. is doing a leak down more acuurate than the airlift system holding vac for 20 min?
Ill be flushing the system out in the next day or 2

 

[Rearanger]

The coolant would go over to the overflow tank and blow the top off of it.

When?

 

[Karenvinn]

In the morning mostly.
When it first started to occure the antifreeze was dark brown and dirty as if some tried stop leak to it. or it was original antifreeze 138000 miles.

I just drain the expansion tank clean the tank and filled the coolant up. also made sure the hose wasn't clogged to the overflow tank. I let im warm up. with out radiator cap 10 15 min. started to push fluid out . re installed cap. look in overfloww tank I was getting a bubble every 7 -8 sec. Took it for a hard ride. 15 20 min temp normal heat was very hot. Got back look into overflow tank and we had consistant bubble. Relieved the pressure top off antifreeze started her up removed the radiator cap saw no bubbles at the filler neck.

I'm little confused where to check for bubbles.at the overflow tank or filler neck? And if it were a had gasket why didn't I loose vac when i used the airlift system. isn't it almost the same as pressurer testing except only with vaccume? I will pressure test and do a leak down test in the nexk couple of days. One question when doing a leak down test how much air pressure should I send through the cylinder? and do the valves need to be closed?

 

[Karenvinn]

Also there are no visble leaks around the head and no white smoke out the exhaust.

 

[Rearanger]

Have you tested A/F for exhaust gases - kit from auto parts?

 

[Karenvinn]

No I haven't Ill pick one up. Wouldn't it overheat if it were to be a head gasket?

 

[Rearanger]

The coolant would go over to the overflow tank and blow the top off of it.

That is overheating.

Got back look into overflow tank and we had consistant bubble.

Air or exhaust gas is being introduced into coolant.

 

[Karenvinn]

How is that temp never gets higher than 195? Now the heat just goes cold and temp gause goes to cold. Then it returns to normal and hot heat again. Im going to autozone and get one of those kits.

 

[locovaca]

How is that temp never gets higher than 195? Now the heat just goes cold and temp gause goes to cold. Then it returns to normal and hot heat again. Im going to autozone and get one of those kits.

Because a temp sensor can't measure the temp of coolant if there isn't any coolant touching it. Nor can a heater core blow any heat if there isn't any coolant flowing through it.

 

[Karenvinn]

Makes sense. The last time I did head gasket it was on a subaru and temp gauge went right into the red.
I did a leak down test and bad news cyl 5 was blowing bubbles to the radiator filler neck. Guess I'll be changing head gaskets. the question is will the heads be any good to use. Its been doing this for awhile and since it never got into the red zone, didn't smoke and truck didn't miss a beat i drove it. Think they will be good if they are just shaved down?

 

[Rearanger]

the question is will the heads be any good to use.

You won't know anything until the heads are tested.