Thumping in cooling system

cdxhizors · Feb 5, 2016

I've been fighting this since I put the new water pump on. It happens when fully warm. You can see the heater hoses move when it thumps and can feel it most around the thermostat. Thermostat is new and so is the waterpump. I've been trying to bleed all the air out and thought all was well this whole week until today when it started thumping again. Any ideas of what to do next? The thermostat had the air hole and was upright. I replaced the cap also.

black_demon69 · Feb 5, 2016

do glove test on COLD engine if it dances you have a bad/cracked head or head gasket. if not try raising the front of the truck and run until t stat opens then top off. could also be a partially blocked heater core or radiator.

cdxhizors · Feb 14, 2016

Ok so I'm sick of this truck. This problem is crazy. The glove test passed. No dancing. I drained and refilled to try to get the air out. And now I get thumping only when I use heat. And as soon as I turn heat on you can watch the temp gauge go from about half to the line at C. As soon as I turn the heat off it'll go right back to normal. Wtf?! Any ideas?? I'd surely appreciate it.

txgocartB3000 · Feb 14, 2016

Sounds like air in the system.

Buy a Lisle no spill funnel kit for refills.

Look at u tube for videos on how to use it.

Ray

RonD · Feb 14, 2016

You need to remove one heater hose from the firewall, engine cold, rad cap off, then fill system until coolant comes out hose and its fitting on the fire wall, that will get most of the air out, the rest will self purge.

Right now you have a "air dam" in the heater hose/core.
If there is a by-pass valve, 4 heater hoses, then manually push open(with finger) the valve while filling, you will then see coolant flowing in and then out of the open ends.

The heater connections on the firewall are often above rad cap level, this is OK IF(big if) you get most of the air out of the core and hoses, you do this by removing one hose to let the air out.

cdxhizors · Feb 14, 2016

RonD said:
You need to remove one heater hose from the firewall, engine cold, rad cap off, then fill system until coolant comes out hose and its fitting on the fire wall, that will get most of the air out, the rest will self purge.

Right now you have a "air dam" in the heater hose/core.
If there is a by-pass valve, 4 heater hoses, then manually push open(with finger) the valve while filling, you will then see coolant flowing in and then out of the open ends.

The heater connections on the firewall are often above rad cap level, this is OK IF(big if) you get most of the air out of the core and hoses, you do this by removing one hose to let the air out.

I've replaced that bypass valve so I'm familiar with the area.. Which hose should I fill the system with? The inlet or outlet of the heater core? And also would moving the hoses temporarily lower than the rad cap help?

RonD · Feb 14, 2016

Doesn't matter which hose comes off for refilling, if you ever back flush heater core then it matters.

Removing the hose gives the air in heating system a chance to move out of that section.
When you refill via the radiator cap opening you end up with equal pressure at both heater hoses as the engine and rad fill up, there is no flow so no in/out when refilling, any air in the core is trapped there, and once there is flow it often can't be pushed out, so you get the thumping.

You can remove one of the core hoses at the bypass as well if it is easier to get to.

kimcrwbr1 · Feb 14, 2016

Put a flushing tee in the heater hose on the intake manifold and add water to the tee until it runs out of the radiator. Hold the tee up above the radiator and quickly put the cap on the tee. That fills the upper engine, heater core and bypass hose.

cdxhizors · Feb 14, 2016

Should I drill a 1/8 hole in the thermostat? I've done that before which helped but not sure as the bubbles seem to be in the heater core.

kimcrwbr1 · Feb 15, 2016

http://cgi.ebay.com/ebaymotors/Prestone-Antifreeze-Coolant-Flush-N-Fill-Kit-Cooling-System-Back-Flush-AF-KIT-/161935041296?hash=item25b414a310:g:Lz8AAOSwT4lWR8JI
Try the tee in the heater hose first didnt you say the thermostat already had a small hole? thats all thats necessary. You will know when it is good when the heater starts working real good. The circulating pump only creates a flow real low pressure the bubble in the heater core also goes through the bypass hose like a loop and it keeps the coolant from flowing through the radiator. It is also possible the impeller on the water pump is shot maybe worth replacing the pump to eliminate that variable?

Andy D · Feb 15, 2016

He just put in a new pump. That is when the trouble started. To OP, patience, run the heater and the engine for a 1/2 hr 45 minutes,You are looking for a dropp in the level in the radiator. That means it burped and when you top off, you're done.

RonD · Feb 15, 2016

cdxhizors said:
Should I drill a 1/8 hole in the thermostat? I've done that before which helped but not sure as the bubbles seem to be in the heater core.

Most thermostats now come with a "jiggle valve" which is the 1/8" hole you mention, the "jiggle valve" has a metal pin in it that "jiggles" with the flow of coolant and that keeps the hole open.
But yes, always add the hole if one isn't present.

The hole needs to be mounted at the 12:00 position, where air would be, this allows air to escape from behind the thermostat when it is close.
So very good to have this hole or jiggle valve when refilling cooling system as it allows air to escape.

But once engine is warmed up the thermostat would be open and air would be able to get out.

As you said, this wouldn't help with air trapped in heater hoses though, thermostat is usually well below the level of the heater core hoses.
Air does not like to leave a high spot, lol, it takes quite a bit of pressure to force air DOWN a hose, and hard to stop it going UP a hose.

cdxhizors · Feb 15, 2016

So far I've replaced the water pump(which is when it started), thermostat, intake gaskets, heater core bypass valve, and radiator. I'm messing with it now. I'll update with what I find.

cdxhizors · Feb 15, 2016

So I completely drained and then refilled using a flush tee on the top heater core hose.. Put the hose back on the bypass, zip tied the bypass open and then ran the truck up to full temp(watching live data on my scanner) and topped off. Of course heat was on full blast while I did this. Everything seemed fine. Then on the drive home it started thumping again. And the gauge is sweeping when taking off. What now? Btw am can I do any harm driving it while it's doing this? I've been driving it for a couple days but wanna make sure before I screw something up.

kimcrwbr1 · Feb 15, 2016

Have you replaced the radiator cap? Is the tube for the overflow tank clear? When it goes high pressure the coolant stops circulating.

Thumping in cooling system

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