cooling system makes rumbling sound....

[ellisjay2]

After driving and parking I notice I hear my coolant rumbling/ making noiling sound, Ive checked under the hood when it does if for a few seconds or so, theres no coolant leak, engine doesnt run hot, recently replaced water pump, sounds to me like its some kind of vapor lock issue or could it be air in the system?? Recentley did cooling system flush with vinegar to remove rust debris from left over non distilled water staying in system. Heat blows heat as it should... im guessing its something minor, just would like some input on what could be causing it to boil/rumble.

[geezer#99]

Rad cap is toast or your level is low.
Is your return bottle working like it should?

[Lost81c10]

just from my own experience...
when you did your system flush and during refill, did you turn the heater on inside the truck at full blast while you were filling it?

[ellisjay2]

Originally Posted by Lost81c10

just from my own experience...
when you did your system flush and during refill, did you turn the heater on inside the truck at full blast while you were filling it?

Yep, had heater on full blast everytime, Ive flushed it maybe 4 times in the last two months, but now im considering my radiator cap maybe bad as it has rust particles on the bottom of it and is harder to put on and take off now.

[slikside]

Bumping this thread cuz this is the exact issue I'm having.

So ellis, did a new cap fix it for you?

Mine is making "growling noises" on startup and/or at acceleration from a stop. Maybe even after coming to a stop.

The good news is that the temps are completely normal. It works just as it should, but the noise is bothersome.

[slikside]

Originally Posted by geezer#99

Rad cap is toast or your level is low.
Is your return bottle working like it should?

Pretty sure the cap is good, so maybe I am low on fluid. I know it never pukes anything out the expansion hose. I don't have a return/overflow bottle, never have. But this is the first time I've had this issue.

Originally Posted by Lost81c10

just from my own experience...
when you did your system flush and during refill, did you turn the heater on inside the truck at full blast while you were filling it?

Don't recall if I actually did this or not, it's been a few years...but unless you have an actual shut off valve on your heater, will this make any difference??

I redid my entire cooling/heating system all at once (heater core too). What I learned is that unless you have one of those valves (I don't), hot coolant is continuously circulating to the heater core. You simply open the door on the firewall with one lever and turn on the fan with another in order to get heat into the cab. So, "running the heater" while filling, is not really changing anything from a coolant flow perspective, is it?

[gchemist]

You have in the heater core. Not ideal. If it boils enough, pressure builds and it could blow your heater core.

[slikside]

Originally Posted by gchemist

You have in the heater core. Not ideal. If it boils enough, pressure builds and it could blow your heater core.

OK, I believe that. Explains why it's so easy to hear!

So what's the best way to get air out of the heater core??

By the way, I found this thread through the search feature. I didn't realize it was in the '73-87 forum until I posted, and went looking in the '67-72 forum, which is really where I hang out. I wasn't there.

[ellisjay2]

Originally Posted by slikside

Bumping this thread cuz this is the exact issue I'm having.

So ellis, did a new cap fix it for you?

Mine is making "growling noises" on startup and/or at acceleration from a stop. Maybe even after coming to a stop.

The good news is that the temps are completely normal. It works just as it should, but the noise is bothersome.

yeah new cap solved my issue, old one was warped up on inside of rubber, i guess from when i was battling the rust in collant system.

[slikside]

Originally Posted by ellisjay2

yeah new cap solved my issue, old one was warped up on inside of rubber, i guess from when i was battling the rust in collant system.

Good you got it figured out. I don't think that will be my issue (not that lucky!).

[slikside]

So what's the best way to remove air from the the heater core?

I'm thinking about breaking loose the top heater hose where it attaches to the water pump, raising it as high as it'll go, and then slowly filling with coolant till it's full. Then re-attach. I'll loose a little fluid making the connection, but it should improve things, shouldn't it??

I'm open for any better ideas. Thanks.

[craig113]

I have a suburban with a rear heater, getting the air out was hard, what I found out, was to park the right front tire on the hill or vehicle ramp with the radiator cap off over night. Removed the cap when warm. Next morning when I came out I added a 1/2 gallon. As it cools at night it circulates and pushes the air to the top of the radiator.

[slikside]

Originally Posted by craig113

I have a suburban with a rear heater, getting the air out was hard, what I found out, was to park the right front tire on the hill or vehicle ramp with the radiator cap off over night. Removed the cap when warm. Next morning when I came out I added a 1/2 gallon. As it cools at night it circulates and pushes the air to the top of the radiator.

Hmmm, sounds easy enough. I'll keep it in mind.

Thanks Craig.

Any other suggestions?

[slikside]

Originally Posted by craig113

I have a suburban with a rear heater, getting the air out was hard, what I found out, was to park the right front tire on the hill or vehicle ramp with the radiator cap off over night. Removed the cap when warm. Next morning when I came out I added a 1/2 gallon. As it cools at night it circulates and pushes the air to the top of the radiator.

Well, I got around to doing this last night and.....it worked! No more growling!

When I took off the radiator cap the motor was still warm. Gave the upper heater hose a squeeze just out of curiosity and, blub, blub. Sounded like air bubbles to me. It was still warm enough for the thermostat to be open I guess. Still jacked up the right front, and put a stand under it for the night.

Today I put just a couple pints of coolant into it. I have to leave it a couple inches below the top because I have no expansion tank. So, it was a little low, but not a lot.

Any way, thanks again Craig.

[craig113]

Welcome, now if we can drain it all, like cleaning a buck that is hanging to be butchered.

[slikside]

Yeah, I can see where that would be a problem on a heater located that far back. Never realized they had their own heaters way in the back on those Burbs. Makes sense after think'n about it.