Noisy Heater Core

Hi,
I've got a crackling / snapping / rattling sound coming from my heater core in my daily driver 85 Caprice 305. If I pinch off one of the heater hoses,
the noise stops. The noise comes on acceleration, and at a slight rev in neutral. I can't hear it outside, looking at the engine. Too much noise.
Causes I can think of :
1) Steam is forming somehow in the cooling system, and I am hearing the old-fashioned steam radiator sound in the heater core. 2) Air bubbles are trapped in the heater core and are slapping around in there. 3) A piece of debris (metal? ) is flopping around in the htr core.
Additional info : I do have a coolant leak at the rear of the intake manifold. I suppose air could be getting in there.
The car is an 85 Chevy Caprice. The heater core is only 3 years old.
Any ideas ?
Thanks,
L
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Lecher9000 Spilled my beer when they jumped on the table and

How long since a flush-n-fill?
NOI
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About 4 or 5 years. I haven't flushed or drained it since then, since it leaks so much from the back of the intake manifold that I know the a/f is fresh, since I am always topping up the reservoir. :) But of course any junk that is in the system stays there. Yeah, maybe some debris is rattling around in the heater core. To get it out, I think I would have to remove the core and turn it upside down ! What a PITA. Or maybe backflushing the core, in place, would send the debris back out.
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snipped-for-privacy@aol.com (Lecher9000) wrote in message

There is a small plastic restrictor that you can put in the intake side of the heater core to stop this problem. The newer Chevy trucks actually have some kind of bulletin out on that very subject. When I worked at the local autoparts store, I remeber them bring in te "HELP" line of products. Its a very common occurance in all kinds of vehicles.
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Hey, thanks, guys, for the replies. Sounds like no amount of flushing / bleeding / pampering will make the sound go away, eh ? It's good to know it is a common problem. The core is about 3 years old. Wonder why it has started to rattle now. It never did fit into the "snap-in" connector right, when I installed it. I had to just rest it on top of the connector. But it never rattled for 3 years. I hope it's not destroying my core.
How does the restrictor work ? Less volume of coolant flow doesn't allow the rattle to happen ?
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know it

started
I
the
The restrictor does just what is says...it restricts the flow so that the turbulence being created does not resonate in the vehicle.
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my
hoses,
of
manifold.
Dont laugh, this is a common issue. I had the heater core in one of the vans go FUCKAAAAAAAAAAAAAAAAAAAA on the way to a very cold and distant job one night about 10pm. The new heater core was in place in about 20 minutes (Fords only better idea) and when we got it in, all was fine and dandy till hiway speeds...we looked, and looked and looked, and while it was making a hell of a noise from the air pump, we automatically assumed it was toast. We replaced it...since it was cheap and easy as hell too....and sure enough..silence...till hiway speeds..then the freaking dash sounded like it was gonna come out. After bitching like hell about the problem, we pinched off a heater hose since you could not hear it outside but only in the cab, and bingo..that was it. We bled it to insure no air was in it..and since the damn quick connects had broken, we had clamps on so it was easy. Put it back and the noise was still there. Put a new core in (this thing was one day old, I was not goinna buy the restrictors when the OLD one didnt) and sure enough...gone. Its more common than you think.

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