Fishnaked

I have a 1995 F150 XLT, 4x4 Super Cab, 5.8L, auto trans, 83,000 miles. The coolant is going to the overflow but not going back to the radiator. Even after sitting for 48 hours, the coolant level is way above the "cold" line while the level in the radiator is down.

Why is the coolant not being drawn back to the radiator? Do I need a new radiator cap?

88xlt

Possibly you need a new radiator cap. My first thought though was that the small tube running from your radiator to the overflow tank is not airtight. The coolant can flow into the overflow tank but the hose is not airtight to draw the coolant back to the radiator. My bottom line suggestion, check the ends of the hose where it connects to the radiator and overflow tank first.

Steve83

Put all the truck's details into your signature as this caption explains:


(phone app link)Possibly because there's enough coolant in the engine already. It's possible to OVERfill the engine/radiator, and also to OVERfill the overflow tank. That would certainly produce the effect you're describing, but it wouldn't mean there's an engine problem. It would just mean you're doing something wrong.

Is the truck exhibiting any specific problems related to the coolant? Does it purge more coolant to the overflow tank every drive cycle (for more than 4 cycles)? Or does the overflow level stabilize after a few drives/cooldowns? If so; it's fine - don't worry about it.

If you want to know how the coolant system works, click this & read the caption:


(phone app link)How could we know? You didn't tell us anything about any tests you've done (or had done) on the cap. You didn't say how old it is, what brand it is, what PN it is, how many miles are on it, if it's physically damaged...

raski

After sitting overnight, is the coolant up to the top of the radiator neck? If so, you are fine and the system is slightly overfilled in the bottle.No problem. If not, I would pressure test the system and test the cap.The cap is cheap and if its old, just replace it with a name brand. I believe the auto parts stores have the tool to do so. You need a tight system including the mentioned bottle hose and all radiator hose clamps. I use a small ty rap to ensure a good seal on the small hose..

Fishnaked

No it's not, hence my original post. The coolant is not returning to the radiator from the overflow tank.

I drained the coolant from the overflow and took off the little hose. It and its connections look fine. So I put it back on and topped off the radiator.

Thanks.

Fishnaked

I drained the coolant from the overflow and took off the little hose. It and its connections look fine. So I put it back on and topped off the radiator.

Thanks.

Fishnaked

I'd have to monitor it some more to be sure but I think it just keeps purging coolant to the overflow tank without stabilizing.

What should the level be in the radiator itself? Here's what I've been doing: When I can't see coolant in the radiator, I pour it in until it reaches the bottom of the neck. I drive, let cool, check, and if I don't see coolant.... I add again. Meanwhile, the coolant level keeps increasing in the overflow tank.

Thanks.

Brokemillwright

As mentioned earlier the level should be up to the filler neck. Rad caps are like $10, just go buy one. If you just worked on it and didn't burp the system I wouldn't be suprised if there was an air pocket. Worst case scenerio pour some gas on the seat and light it on fire

Fishnaked

Thanks. How do you burp the system?

Steve83

Fill through the radiator neck, then put a good cap back on it. Remove either heater hose from the firewall nipple, fill through the hose until it starts to spill out the nipple, then quickly reconnect the hose.