Head gasket? full overflow catch bottle

My van has been having an issue with disappearing coolant all summer and three mechanics have confirmed there are no external leaks. Passes pressure test, vacuum test. The opinion is that it is the head gasket.

About ready to pay for the head gasket but nervous since our van doesn’t have any of the smoking gun signs. We already paid a lot to change the thermostat because we were told by a different mechanic it was leaking, but that didn’t change anything.

The van passed the carbon test (the fluid is pretty new though and I know it’s possible to have a pin hole in an area where no mixing occurs) There is no smoke, no smell, no overheating. It sometimes has a small amount of pressure in the system after cooling and it has a small amount of bubbles in the expansion tank, but nothing like what I see in videos of these problems. The low coolant light is usually on. It comes on between 10-40 miles of filling the tank. And the fluid is usually slightly below the min line most of the time, but I drove 200 miles with the fluid around that level. Never overheats.

Today I rigged a catch bottle and this is how it went. After filling to slightly below the max line and letting the car idle until it reached 180 and didn’t see bubbles, I put the cap on and I drove 10 miles on the highway and the sensor was flickering on and off, but mostly on. I pulled over and a liter of fluid was expelled into my catch bottle. I put it back in the tank to see how much was expelled vs burned off in the head gasket and it looks like all of it was expelled. I’m going to try experimenting with it at the min line and see how much ends up in the bottle next. I saw a lot of debate about whether the reservoir should be filled to min or the max line when the engine is cold or at least cold enough to safely open the radiator cap.

I know this can be a head gasket symptom? Could it be anything else? Is my sensor too sensitive? Should it be on when the fluid is at or slightly below the min line? Also at the bottom of the brand new catch bottle was some brownish stuff, rust?

Would love to hear some thoughts.


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Do you ever notice a sweet smell from the exhaust pipe?

Has the pressure cap been changed? There have been reports that it can be wonky and still pass a pressure test.

I converted a 3.3L Dodge engine to a reservoir type system. It wasn't losing coolant, but would suck air during cool down which would get cause air pockets and overheating. I suspect that the air intrusion was something to do with the coolant pump seal, but the pump never failed. The reservoir method cured that problem.

Converting isn't a repair, but could be a temporary "fix". I had a dodge V8 with a cracked head which was fine on trips, but would use coolant around the city. I believe the crack(s) sealed when the engine heated to operating temperature. Keep in mind that if coolant is getting into the combustion chamber it could cause problems over time.

vic

So I did change the cap, it’s the third one actually. A shop gave us one that didn’t release pressure and caused some hoses to burst before I found the cause with help from the forum.

There is no sweet smell. It doesn’t seem to have any fluids mixing at least from the test results. One question though. If the head gasket combustion gas is the cause of a liter of fluid being pushed out of the expansion tank hose shouldn’t it fail a block test? Mine the test fluid color remains unchanged, used a diesel specific one.

Also, a few weeks ago the heater would only work out of the passenger side vents, now it works on both, maybe an air pocket issue?

The idea of converting the tank sounds interesting, but probably beyond my knowledge level since the current one is built into the radiator. Or could I just extend my hose to the bottom of the catch bottle and have it pull up fluid?


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Rae25 said:

...Or could I just extend my hose to the bottom of the catch bottle and have it pull up fluid?
...

Click to expand...

That's basically it except that you need to change the radiator cap to a reservoir system type. That style cap holds pressure, but has an extra valve which allows coolant to be sucked back into the system when the engine cools. I believe that I used a windshield washer fluid bottle from some small car for the overflow tank.

Changing the system type didn't hurt the 3.3L petrol engine operation. I don't know if there are any negatives to changing the system style on a Sprinter. There may be some affect on the antifreeze being that the coolant in the overflow reservoir bottle is constantly exposed to ambient air.

Be certain that whatever cap you change to has the same pressure rating.

vic