nardey11

So recently I've noticed that after my 2000 gets hot and I turn it off there is a gurgling noise coming from the engine and bubbles in the overflow tank. There is no froth in the oil and when i take off the oil fill cap there is no evidence of coolant at all. Could it be the head gasket starting to go or does the system need to be purged. It has 182k miles and I'm a new owner so I dont know if it blew at one point, I can tell that there is a new valve cover gasket if that means anything.

DFlintstone

You could be fine, just running a bit hot. When you park and it boils a bit, it's natural that it would bubble in the tank. I might make sure my coolant is 50/50 and the rest of the system is up to snuff. (E-Fan works..has fan shroud ect.

A head gasket test is to remove the cap and fill to the top, then power-brake it and see what it does. Some surging is normal. A geyser slamming into the hood, not so good.

extrashaky

That is a symptom (but not a guarantee) of a blown head gasket or cracked head allowing exhaust into the cooling system. You have to take potential head issues very seriously with a 2000 because it has the 0331 head, which has a known issue with some of them cracking. There is a LOT of information about the 0331 heads if you search. Not all of them crack, however, so prove it out with tests before you take action.

To rule out an exhaust leak, you use something like this:

Combustion Leak Detector

There are several of those kits on the market, so you might find a better or cheaper one if you shop. Also, a lot of mechanics have these kits and can test it for you if you'd rather not buy the kit yourself.

Modern oils do not necessarily get milky or frothy when exposed to coolant. When you shut down your engine, moisture in the air inside the motor condenses out as it cools. The detergent package in the oil is designed to bond to this incidental moisture when you start the motor back up and reduce the amount of damage it can do until the engine gets hot enough to boil it out. Thirty years ago, if you overwhelmed the detergent package with coolant from a head leak, the coolant would be suspended in the oil in a milky emulsion, and you could see it.

Now, however, the detergent packages in some oils have gotten so good that you can't necessarily tell by looking at it that it's contaminated. When my head went, my oil level rose but never turned milky at all. But it was still doing damage.

The only sure way to know is to take an oil sample (hot) and send it off to a lab for analysis. I use Blackstone, but there are others. It costs $28 and they send you a sample collection kit for free.

If it turns out NOT to be a head issue, you would probably do well to give it a complete cooling system overhaul: radiator, radiator cap, water pump, thermostat, hoses and fan clutch. With a 2000, however, I would make sure that head is good before proceeding, because that can make a difference in what you ultimately decide to do with the vehicle.

DFlintstone

Good point on the 0331 head. That said, any rig with an overflow tank might gurgle some into the overflow parked hot...especially if the antifreeze, (and anti-boil) is not up to 50/50. (that is partly why it has an overflow tank).

Having a shop "sniff" your radiator for combustion gasses might be prudent. If that 0331 is cracked and coolant gets in the oil, it will indeed do a number on all the bearings in the engine.

97grand4.0

What ever happened to the good old radiator pressure tester? Put in on where the radiator cap goes, pump it up, and see if there is a leak. Cheap and effective. However, the hydrocarbon test for antifreeze would likely be helpful as well, just not as available.

DFlintstone

I gather it can be done with any smog tester. No idea of what ppm HC is OK in the rad, if any. Anytime it boils and the pressure exceeds 16-18 Lbs or so, it's gonna bubble in the overflow, 0331 or not.

Radi

If it bubbles with the engine running, worry about the head gasket. If it only bubbles shortly after you turn it off, fix your cooling system.
There is no cylinder pressure behind the head gasket after you shut the engine down.