Losing antifreeze out of coolent over flow

Why am i losing coolant out of overflow on a 1999 jeep Cherokee classic for ?

If coolant is being pushed out of the tank it’s usually a head gasket. Get a pressure test done along with a compression test.

@texases Yes, the overflow is designed to catch the expanded coolant only and that is what is sized for. A head gasket breech put a lot of pressurized gas into the cooling system and forces out more coolant than usual. It’s like a kettle boiling over.

If you are lucky it may just be a radiator cap that’s not holding pressure.

Ed B.

Good point, I’d try a new cap first, just in case.

Good comments so far and this is another vote for a new radiator cap first. If it doesn’t work then I’m afraid you have a bad head gasket. Good luck.

Ty all and if u all can post anything else please do as iam not a mechanic! Ty

Why am i losing coolant out of overflow...

You do mean out on the ground, and not just disappearing from the overflow tank, right?

Do you have a dashboard engine coolant temp gauge? Where on the scale is it reading after the engine is warmed up? Is the radiator fan coming on like it should in stop and go driving, and like when waiting in the drive-through line at McDonalds?

If the coolant simply gets too hot, this can be the result. I had a similar problem on my Corolla one time & it was the coolant-temp-switch that was supposed to turn on the radiator fan. It had become intermittent and didn’t come on sometimes.

Suggest to keep an mindful eye on the coolant temp gauge; if you can tell the folks here in what situations the gauge goes over its normal temp reading, that could provide some clues.

Ask your mechanic to make sure that your cylinder head gasket surface is flat. If it is an OHV engine, then it can be milled flat for a good seal. If you have an OHC engine, then no more than .003" can be milled from the sealing surface to get the head sealing surface flat. If more than .003" is needed, then your head is warped too much and the cam bearing can be ruined due to misalignment. This is how it works with a VW. If the aluminum OHC head is warped too much, then it needs to be heated and pressed back to flat.

I agree… try a new pressure cap.

If the pressure cap doesn’t work, there are three simple tests you can make to see if you have a bad headgasket.

The first is to, with the cooling system filled and purged, simply look into the radiator fill hole with the cap off and the engine running. If there are bubbles coming up, that’ll be the combustion gasses blowing through the headgasket breech and migrating up to the highest point in the system, the fill hole.

The second is what I call a “lab test”. It’s a chemical test of the coolant in the radiator for evidence of hydrocarbons from the combustion chamber(s). The kit is cheap, can be purchased at any parts store and comes with instructions. It’s easy to use and pretty definitive.

The third is a pressure leakdown test of the cylinders. Basically, you’re just installing a fitting in each sparkplug hole one at a time with the crankshaft turned to where both valves are closed, pressurizing the cylinder with air, closing the air supply off, and monitoring a pressure gage to see how well the cylinder is holding pressure. Again, the test is simple and the kit with fittings and instructions is readily available at any parts store. This test is considered the “final word”, but you may know the answer by the other two tests before you get this far.

If you do have a headgasket breech, and you decide to replace the headgasket, that’s the point where you need to be concerned about surface flatnesses. But personally, on a '99 Jeep, I’d go looking for a boneyard engine. You didn’t say how many miles the Jeep has, but I’m assuming it’s in the six figures. Apologies if I’m wrong.