New Member, tracing coolant loss

[VelociRanger]

I own a 2002 Ford Explorer with the 4.0, it has 190k miles. I’ve been trying to diagnose a coolant leak for a while. At first it would start to over heat occasionally so I replaced the thermostat, but noticed I didn’t drain the correct amount of coolant from it, then watched the reservoir level and noticed it would drop after a couple days. I found the heater hose T connection was cracked and spewing coolant, so I replaced it. Then we started losing coolant again, so I pressure tested the radiator cap and it didn’t hold pressure so I got a new cap. Reservoir stayed full for a while, no issue. Now suddenly it’s losing coolant again, with no visible leaks. Oil isn’t milky, no smoke on start up, no rough idling, no signs of head gasket other than losing coolant. Any help would be appreciated, thanks.

 

[Mike65]

Welcome to the forum. Check for any signs of a leak at the thermostat housing, they are famous for leaking.

 

[BrooklynBay]

Welcome to this forum! Connect a cooling system pressure tester to test the system for leaks. Autozone has them with their tool loaning program.

 

[Josef161]

It could be the coolant reservoir cap ($5-10) or the water pump.

 

[Mbrooks420]

It could be the coolant reservoir cap ($5-10) or the water pump.

How do you lose coolant from the reservoir cap? The radiator cap was replaced as noted in the original post.

I agree with BrooklynBay, it’s time for another pressure test.

 

[Josef161]

How do you lose coolant from the reservoir cap? The radiator cap was replaced as noted in the original post.

I agree with BrooklynBay, it’s time for another pressure test.

Maybe it's the same thing, I've never seen a radiator cap in my explorer. But the cap on the coolant reservoir is supposed to open if the pressure reaches a certain level and i have heard that the spring in the cap can get weak over time and then it opens up too early, this can couse steam to escape. That's how my understanding, is that right? And i didn't read that he changed his radiator cap...

 

[VelociRanger]

Been a while, I changed the water pump recently. Leaks went away, but then they came back again. Tried the dye again, but I can’t pin point it this time

 

[Sho-Tyme]

Go around and check all the hose clamps. When it cools down, they'll tend to sometimes leak, they'll look tight, but you'll get 1/2 to 3/4 of a turn on them.

 

[VelociRanger]

It only leaks while running. I thought that too, I thought maybe I didn’t put them on right when I did the thermostat but no, I can at least confirm it’s not from the hoses

 

[Davies0202]

It only leaks while running. I thought that too, I thought maybe I didn’t put them on right when I did the thermostat but no, I can at least confirm it’s not from the hoses

Just to add another spot to check if you have any of the aftermarket intake manifolds tucked behind cylinder 4 is a litte rubber coolant dinky cap. The stupid cap pops off and let’s all the coolant out when it comes loose. I just caught mine starting to slide off again yesterday lol but the rubber can crack and either spew a tiny leak or just all out fail Edit: sorry I cannot read and didn’t see you have a 4.0 lol