Coolant hoses thumping heartbeat noise

[Chris 71 K10]

I looked around some but did not see this mentioned so sorry if it’s been covered. My 71 K10 with heater no ac has a thumping noise like a heartbeat. You can feel the pulse of the coolant making the noise in the hoses to and from the heater core. You can hear it in the cab and sometimes it’s louder than others. Anyone know why it’s so noticeable or anyone have this occurring or fix this issue before?

[sick472]

Is it possible that your lower radiator hose is collapsing, letting go, and re-collapsing?

OR, could it be a head gasket that has given away allowing the combustion gasses to surge into the coolant system?

OR, a surging thermostat?

OR , a failing water pump?

I've never witnessed "heart beat" in the coolant lines...very interesting.

[kazoocruiser]

Maybe your water jacket has air in it. I would check the water level in the radiator to verify it isn't low.

[Sheepdip]

Pull the thermostat and drive it to see if it goes away. Simple, quick and easy to do.
A stuck or malfunctioning thermostat will cause a hammering problem like you describe.

[noxqsz]

I'm not much of an expert on anything, but I don't recall ever seeing heater hoses routed like the ones on this engine. Usually one hose goes from the water pump to the heater core and one hose goes from the intake manifold to the heater core. Never seen a heater hose that goes to the radiator. Also never seen a radiator that has a heater hose outlet or inlet. What that might have to do with the symptoms being experienced I can't say but...?

[Sheepdip]

Originally Posted by noxqsz

I'm not much of an expert on anything, but I don't recall ever seeing heater hoses routed like the ones on this engine. Usually one hose goes from the water pump to the heater core and one hose goes from the intake manifold to the heater core. Never seen a heater hose that goes to the radiator. Also never seen a radiator that has a heater hose outlet or inlet. What that might have to do with the symptoms being experienced I can't say but...?

Actually it's pretty common, and the hoses are routed correctly with the hotter water off the intake into the lower connection as hot water rise's and helps push it thru the core out the top and back into the radiator to start the cycle into the water pump again.

[Chris 71 K10]

Thanks guys! It works great, heats the truck well and keeps the engine cool so I’m probably just being nit picky.

[Sheepdip]

Originally Posted by Chris 71 K10

Thanks guys! It works great, heats the truck well and keeps the engine cool so I’m probably just being nit picky.

Confused here....did you fix the problem or are you just telling us how good your heater works?

[geezer#99]

Originally Posted by Chris 71 K10

Thanks guys! It works great, heats the truck well and keeps the engine cool so I’m probably just being nit picky.

Good heat or not, change your rad cap.
Looks like you have a quick release lever type cap.
They’ll make your coolant system do that.

As for hose and flow routing, intake to bottom of core, top of core back to water pump or to the rad if your system is heavy duty.

[El Dorado Jim]

sub'd

[Chris 71 K10]

Originally Posted by Sheepdip

Confused here....did you fix the problem or are you just telling us how good your heater works?

I didn't want to respond too quickly but I replaced the radiator cap and the thermostat (OE spec style same as before) and it does seem to have subsided. It was not causing any sort of issue before and I have been listening for it everytime I drive and its my daily driver so I think between those 2 things its good. If it happens again I will let ya know.