Gurgling behind dash
 

Hey guys got a question, I have a darn gurgling noise behind the dash! Now I have read different things on this, it has been doing this for awhile, like as in about 4 months or more. Any way i've read head gasket, air in the system and heater core! Now I did have a t-stat problem. But I fixed that, it was about a week ago. But the noise was there before that! It doesn't overheat and the heat works good! Also I see no water in the oil or anything. By the way it is a 97 F150 4.6 extended cab. It runs fine it's just when I step on the gas it does this. It has me baffled right now, any ideas would be greatly appreciated! Thanks guys!

I would test the coolant for hydrocarbon gases , If nothing else to confirm or rule out the head gasket. Pretty suspicious that it gets worse with heavy acceleration. Otherwise I would suspect the heater core

doing a pressure test is good. The hydrocarbon test checks for exhaust gases in the coolant, which would point towards a weak head gasket. Yes this can go on for sometime before something catastrophic happens.

Agreed ...in either case there is a lot of work involved.

Yeah sorry forgot the name of the test even though you had said it, lol hydrocarbon test I mean. I might try to do a direct heater core flush first just to see what happens? If I get a day if it gets a tad warmer it's cold here in Missouri I don't want frozen water out of my garden hose lol! Or on the ground! Don't know where you are? But it's probably cold in your neck of the woods? Unless maybe your in Hawaii, thanks again for the advice I just pray it's not a head gasket for sure!

There is air in the system and coolant may be low.
A slow leak may have developed.
Have you looked?
If the system is tight, there will be a vacuum on the cap when removed 'cold'.
If not there is a leak some place.
Good luck.

No low coolant low and there Has always been a vacuum sound when cap is removed and yes I've looked for leaks haven't seen any. And I have tried to burp the system several times, and still here the noise. Even with it on ramps and on a incline with the cap off and the heater on high. I also did a pressure test and it held 16 psi for at least 15 minutes. Thanks for the help!

Only way that sound is produced is air in the heater core with coolant being force by it.
The faster the motor runs the more you will hear it.
Good luck.

Figured, it seems to go away after the first initial push of the accelerator pedal. Thanks again! Like I said everything seems to be fine per say that gurgling is annoying for sure!

Does anyone know what the hard plastic thing is in the heater core inlet hose, is that the flow restrictor? And could that be bad or clogged? Thanks!

Also what if it is removed heard different stories about it? And any idea what you should do if you can't but another or whatever, i've heard folks say it's an obsolete part? I'm just speaking if I had to replace the heater core etc. Thanks!

Yes it is. If you have decent heat when the engine is well warmed up, the restrictor is fine.

It is inside the inlet hose itself, away from an end, and held there with an external clamp, besides it's pressure exerted on the hose wall due to it's outer diameter being bigger than the hose's ID. A quality proper replacement hose will have the restrictor already in it. No reason to ever fool with it.

I believe the inlet hose restrictors were first used when the 4.6L modular engines appeared in the Crown Vic/MGM/Town Cars years before the 1997 F-150.

Thanks for the info! I do have decent heat when it's warmed up I don't have an instant thermometer to see how exactly warm it is? But your certainly not freezing when you are in the cab lol it did get cold once, but the thermostat was bad replaced that. It seems to work ok since then! Has been about a week and a half. Also it did over heat at the time!