Ok let me see if i can try and explain the situation. Last year My heater core started to leak. So, I by-passed it until i could get the money to fix it. I ended up taking it to the dealer to get all that replaced. Once i got the truck back I noticed a hissing and gurgling noise under the dash. I thought that it might be air in the system so i called them up and told them. He said to check my coolant and top it off if need be. He said that the air would work itself out eventually.

I do not drive the truck very often due to the expense of running the 4.7 V8 in gas. But i have driven it probably 6,000 miles since the service. It is still making the noise under the dash, but the coolant is full. I took the truck back to the dealer and made them check it over again. They called me and said that the hissing and gurgling is also happening in the overflow. They told me that my heads are warped and the compression is forcing the coolant in the overflow till it heats up and the noise stops. This noise only happens when i first take off and the truck has to have been sitting for awhile.

So my question is, are they right in telling me that my truck needs heads? the truck runs fine and all works well. it was just annoying listening to that when i first take off down the road. not to mention i figured it was something they did when they replaced the heater core because it didnt do it at all before then.

 

The way I've always been told to release air from the system is this:

Jack up the front end of the truck so it is higher than the back, or park at an angle (on a hill, for example) with the front end pointing up. Unscrew the radiator cap and turn the engine on. Let it idle until warm. Any air in the system will rise towards the highest point, which is now your cap-less radiator, and bubble out. Some coolant may bubble out as well as air is released, this is normal.

Let the engine continue to idle until after the bubbles stop or are barely noticeable, then turn off truck. Fill radiator to full if any spilled out, screw the cap back on (be careful, spilled fluid and radiator may be hot), and see if that makes a difference in your noise.

 

so do you think what they are saying holds any truth to it? i thought it just had air in the system like you are talking about. i didnt mess with it because i paid good money to have them replace the heater core and figured they should have to deal with it.

 

Before paying them more money for heads, I'd try my procedure above. It can't hurt anything as long as your careful about the hot coolant/radiator.

There are many good dealerships with competent mechanics, many dealerships with competent sales people, some with both, and some with neither. You can't always know which one you are using until you've had a few experiences. Sometimes you even get one that is competent with both, but would rather try and force you into buying a new car than fix your real issue.

 

so i started messing with the truck today. I put the truck up on ramps and had the cap off. i ran it like this for a long time. I would squeeze the radiator hose every now and then. I ended up making a pretty good mess though when i gave it a little throttle. throughout the process i did notice some bubbles. i backed the truck down and shut her off and let her sit for awhile. then i put the cap back on and cranked her. the noise was still there. i looked under the hood while it was running with the cap on and looked in the overflow reservoir. i saw some bubbles in the reservoir. the more throttle the more bubbles. So i just went and got a new radiator cap and replaced it. i didnt see anymore bubbles but still heard the noise slightly.

I called another dealership and explained my problem and what the first dealer said. He said that sounded very unlikely. He suggested i go get my truck and try to bleed the system. He mentioned the use of a Lisle Spill Free Funnel? Have you ever used this? http://shop.advanceautoparts.com/p/l...+funnel+funnel It looks legit. However no autoparts place in my area stocks it. So i would have to order it. I dont want to spend close to 40 bucks on something that wont fix my problem though.

I called it a day for now and will go out and check the truck out in the morning after it has sat through the night.

 

I understand the logic, that when cold, there could be a gap and the intense combustion chamber compression would find its way in there. It seems that there would also be a high probability of air being forced into the crank case as well. Would there be a way to check that? Pcv? Also look for mingling of oil and coolant, leaking around the head gasket. Perhaps a compression leak down test. None are definitive, but may provide clues. Very fishy that it was not happening before. I have put many k of miles on cars with bubbles in the coolant system; gurgling the whole time. Good luck, keep us posted.

 

I'm wonderin' if they reversed the hoses in and out of the heater. Don't know if it would make a difference or not. I'm going to have a looksee at our truck later and see if that's easy/hard to do.

 

appreciate the responses guys. i havent looked at it today because it has been raining all day. I still think it is odd that it was fine before and when i get it back it has been doing it. If i cant figure it out i guess ill be taking it to another shop. I kinda hate to because then it will cost me more money. Until something changes i will keep driving it.

 

If it is bubbling that much after all of the purging you have done, and bubbling increases with RPM, you have a problem. Either the head is cracked or one is warped and the gasket is not sealing. Eventually it will suck the coolant in, and you will get huge clouds of steam. If you can figure out which one it is, you might be able to replace just one, using a junker.


Good luck!

 

More throttle = more bubbles? Unfortunately, you have a more serious problem than just bleeding the system. +1 for what northgator8 said. Sorry man.