Coolant and Heater Core Sounds...Normal?

I brought this up over on TN once without too many responses, and I want some more opinions whether this is normal (or anyone else experience this?). For a few years now, I've been living in an area where I travel uphill until the truck is warmed up in the morning. And this only happens in the winter time (likely because that's when I have the cabin thermostat turned to hot).

As the engine begins to warm up and I accelerate going uphill from a stop sign, I will hear the coolant going though the tubes in the firewall (to/from heater core). It sounds like there are air bubbles mixed in. I've never had to add coolant. I've been watching the coolant level in the reservoir and find that it's about an inch higher when the engine is hot vs the level in the mornings when it's cold. It's always between the full and low lines. So I'm not using any coolant.

1. Is it normal for the coolant in the reservoir to rise when the engine is warm and lower when the engine is cold. Or is this a sign that the pressure cap on the radiator isn't working properly?

2. Anyone else hear these sounds when the coolant is first passing through the firewall on it's way to the heater core? Should I be concerned if I'm not losing any coolant? Like I said, I've been hearing it for years in the winter, just finally figured it out this year that it had to do with driving uphill in the mornings.

 

The only time I hear that noise in any vehicle is when coolant is low.

There's air in your system.

 

Whoa. The only time I heard this is when my coolant reserv. was full, but my radiator was about bone dry. If your radiator is almost empty, it won't do a good job of removing fluid from the reserv.

If it's boiling hot and you can hear it, stop, let it cool, pop the radiator cap, top it off. You may be doing extreme damage to your engine.

I'd know, 30 miles after I heard that noise, my engine cooked itself. $6,000 to put a new one in.

You may not have the exact issue, but be safe, top off the fluid in the radiator. A pinhole prick could leak out your fluid and you wouldn't know (that's how mine drained while driving across country).

-will

 

When it's cold, pop the cap off the radiator and check it's level... usually if you're getting air it's low. It's possible the lines are blocked up from the reservoir. Remember if it's been running, if you pop that cap boiling water will fly out at your face.. so only do it well after it's been cold. I personally haven't heard it in my truck...

Also it would be normal for it to be lower cold, higher hot. As it gets hot, the fluid will expand a bit.

 

Truck's been sitting a couple of days (in a 40F degree garage). Popped the radiator cap and it's full to the top (with the extra in the reservoir as I stated before). So there shouldn't be any air in the system which is what has me baffled. I guess I'm the only one with this problem. Well, not too much longer and it'll be time to change the coolant anyway (I'm at 84K miles).

 

Just because your radiator is full doesn't mean there isn't any air in your system. Try this, start with a cold engine and take the cap off the radiator. Start your truck, put on the heat to max and keep the truck on idle. You should see the coolant in the radiator either spill (no air) or go down (air in system). If it starts spilling, put the cap back on. If the coolant goes down, fill the radiator and wait until it starts to almost overflow. Put cap back on. This should solve that sound that you hear.

If not, you should check your thermostat.