Thumping in cooling system

[cdxhizors]

The cap is new.. It's one with a pressure release on it. I blew the overflow tube out. I think there's still air trapped somewhere.

 

[RonD]

What engine do you have?

And by-pass valve engine hoses can have a direction, heater core side doesn't but engine side can have an IN and OUT, this has to do with the way the valve moves inside the fitting

 

[cdxhizors]

What engine do you have?

And by-pass valve engine hoses can have a direction, heater core side doesn't but engine side can have an IN and OUT, this has to do with the way the valve moves inside the fitting

4.0 ohv. Pretty sure I got them hooked up correctly but I'll double check.. Any idea which way would be the in to the heater core? I assume the one that goes to the water pump?

 

[RonD]

On the by pass valve there are two hose connections directly across from each other.
The engine side hose goes to water pump, toward bottom of pump, the other side on by pass goes to heater core
Other engine side hose goes is from lower intake manifold above t-stat housing, by alternator.

 

[jeremysdad]

Starting to wonder if your glove had a hole in it.

 

[cdxhizors]

Starting to wonder if your glove had a hole in it.

Lol well if it was cracked head or head gasket it'd do this all the time not just with the heater core open. I can stop the thumping and gauge issues almost instantly by turning off the heat.

 

[RonD]

You may need to check heater core flow, using garden hose, and see if it is restricted.

Or just loop one heater core hose out of by-pass and back in, this takes core out of the picture and if thumping and gauge issue goes away then core is clogged up.

1995 and up Rangers have heater core buried inside the dash, 5 to 6 hours shop time to remove and replace core is spec.
So if core is plugged up then I would at least try to back flush it and also try to clear out buildup using CLR and hot water.

Good video here on whats involved in '95+ heater core change: https://www.youtube.com/watch?v=vD6gV9C_QSA

 

[cdxhizors]

You may need to check heater core flow, using garden hose, and see if it is restricted.

Or just loop one heater core hose out of by-pass and back in, this takes core out of the picture and if thumping and gauge issue goes away then core is clogged up.

1995 and up Rangers have heater core buried inside the dash, 5 to 6 hours shop time to remove and replace core is spec.
So if core is plugged up then I would at least try to back flush it and also try to clear out buildup using CLR and hot water.

Good video here on whats involved in '95+ heater core change: https://www.youtube.com/watch?v=vD6gV9C_QSA

I'll flush it sometime this week. It's definitely something to do with the heater core.. Like I said I can stop the thumping and gauge fluctuations by turning the heat to off(which closes the bypass valve). I'll try back flushing it. I did see how complicated it is to replace. I've replaced one on a 01 f150 which I feel is about the same difficulty. A multi day project. Thanks for the help and I'll update once I flush it.

 

[RonD]

Feel heater hoses with heat turned on to see which one is the IN from engine, it will be the hotter one, mark it with tape or ??

When you are ready to do the flush, remove heater hoses from by pass valve.
Point the IN hose down at the ground or into a bucket
Put garden hose on OUT hose, back flush it, you will be able to see if it is plugged by the slow flow.

After back flushing, blow out the heater core using your mouth or VERY low air pressure, your lungs can generate 2psi

Mix CLR(or vinegar, not both) with hot water and then pour it into core until it is full.
Let it sit for 20 minutes
Flush it out, see if flow is better
Repeat as you see fit.

 

[cdxhizors]

Feel heater hoses with heat turned on to see which one is the IN from engine, it will be the hotter one, mark it with tape or ??

When you are ready to do the flush, remove heater hoses from by pass valve.
Point the IN hose down at the ground or into a bucket
Put garden hose on OUT hose, back flush it, you will be able to see if it is plugged by the slow flow.

After back flushing, blow out the heater core using your mouth or VERY low air pressure, your lungs can generate 2psi

Mix CLR(or vinegar, not both) with hot water and then pour it into core until it is full.
Let it sit for 20 minutes
Flush it out, see if flow is better
Repeat as you see fit.

Both hoses feel the same and are within 15 degrees of each other( measured with a infrared thermometer). Heat is awesome should I still risk flushing it?

 

[RonD]

That doesn't make sense if core is clogged.

I am wondering if it is the Blend Door making the noise, common issue on Rangers.
Gear gets a few missing teeth and door flaps a bit until closed by turning heat to COLD.

Google: 1997 ford ranger blend door actuator

Almost as hard to get to as the heater core, lol.

That doesn't explain the drop in the temp gauge though, now on a colder day when you select HOT, there will be an initial drop in the gauge, because the cold heater core fluid is coming into the engine, but gauge should come back up within a minute or so

 

[cdxhizors]

That doesn't make sense if core is clogged.

I am wondering if it is the Blend Door making the noise, common issue on Rangers.
Gear gets a few missing teeth and door flaps a bit until closed by turning heat to COLD.

Google: 1997 ford ranger blend door actuator

Almost as hard to get to as the heater core, lol.

That doesn't explain the drop in the temp gauge though, now on a colder day when you select HOT, there will be an initial drop in the gauge, because the cold heater core fluid is coming into the engine, but gauge should come back up within a minute or so

It drops every time I take off almost as if coolant is low and the sensor isn't touching any coolant. It's most definitely coolant related cause when I shut the truck off it keeps going for a few minutes and I can see the heater core hoses thump and can feel it if I grab the top radiator hose. I checked coolant today and it was low so it must have bleed some more from the past day of driving it. I topped it off so we'll see if it comes back. I parked it on a pretty good incline with the heat on idling and it made the thumping stop so hopefully that bleed whatever bubble out of the core.

 

[RonD]

OK that's a new wrinkle, coolant can't be low in rad unless overflow system is not working.

Overflow system is pretty simple and self purges air from radiator.
Coolant expands when heated, like all fluids.

Radiator cap has 2 valves in it, a larger valve/spring is the cap's rating, like 14psi, then a smaller valve/spring in the center, this lets coolant back into radiator.

As the engine warms up the coolant expands, when internal pressure gets above 14psi(assuming 14psi cap rating) the larger valve in rad cap opens and sends what ever is at the top of the radiator out to the overflow hose and into the over flow tank.
"What ever is at the top of the radiator" could be air or coolant.
The over flow hose connects to the bottom of the overflow tank for a reason and the top of the overflow tank is not sealed air tight for a reason, if air comes out it will bubble up and be gone, if coolant comes in it will stay in the overflow tank.

That's the self purging part of the system, any air will eventually make it to the top of the radiator, a high point, and stay there, and be purged at the next warm up.

After engine is shut off and begins to cool down the coolant shrinks, it will get down to -1psi inside the radiator/engine then the smaller valve in rad cap is pulled open and coolant from overflow tank is sucked back into the rad, coolant, not air.
So when you open the rad cap on a cold engine it should be full to the very very top, 0 air, none, nada, zippo.

And there is the wrinkle, air in your rad after warm up and cool down.

First thing I would check is the overflow hose, my 4.0l had a leak in the hose and I was sucking air back in on cool down since it is easier to pull in air than coolant.

I just pulled off the hose from rad cap opening and blew in some pressure, mouth, then held it to see if pressure was lost, it was, hose was cracked, not big but enough for air to be pulled in.

That air should stay at the top of the rad, so wouldn't explain the temp change.

If there is a leak in the engine cooling system then it will leak a bit of coolant but what also happens is that when engine cools down and the coolant shrinks air is sucked in at the leak point instead of coolant via the overflow tank, so no matter how well you air bleed the system more air is being pulled in each drive cycle.

Easiest way to test for a leak is to use a pressure kit, you can rent them.
There is a rad cap fitting with a hand pump and pressure gauge.
You pump up the system to 14-20psi and see if it holds the pressure, if not then a leak is much easier to find on a cold engine with pressure applied, because you can feel around areas that are normally hot, which are the most likely places for an unseen leak, since if they are hot coolant would evaporate fairly quickly not drip on the ground.
Air from this type of leak could cause thumping issues and gauge fluctuations since an air pocket was formed inside the cooling system which would be spread through out the system on start up.

Also with pressure gauge hooked up and pressure applied, disconnect coil pack(no start) and crank engine, similar to Glove test, if pressure gauge fluctuates steadily with engine turning then there is a cylinder leak, and that is what is pumping air into the system.

 

[cdxhizors]

OK that's a new wrinkle, coolant can't be low in rad unless overflow system is not working.

Overflow system is pretty simple and self purges air from radiator.
Coolant expands when heated, like all fluids.

Radiator cap has 2 valves in it, a larger valve/spring is the cap's rating, like 14psi, then a smaller valve/spring in the center, this lets coolant back into radiator.

As the engine warms up the coolant expands, when internal pressure gets above 14psi(assuming 14psi cap rating) the larger valve in rad cap opens and sends what ever is at the top of the radiator out to the overflow hose and into the over flow tank.
"What ever is at the top of the radiator" could be air or coolant.
The over flow hose connects to the bottom of the overflow tank for a reason and the top of the overflow tank is not sealed air tight for a reason, if air comes out it will bubble up and be gone, if coolant comes in it will stay in the overflow tank.

That's the self purging part of the system, any air will eventually make it to the top of the radiator, a high point, and stay there, and be purged at the next warm up.

After engine is shut off and begins to cool down the coolant shrinks, it will get down to -1psi inside the radiator/engine then the smaller valve in rad cap is pulled open and coolant from overflow tank is sucked back into the rad, coolant, not air.
So when you open the rad cap on a cold engine it should be full to the very very top, 0 air, none, nada, zippo.

And there is the wrinkle, air in your rad after warm up and cool down.

First thing I would check is the overflow hose, my 4.0l had a leak in the hose and I was sucking air back in on cool down since it is easier to pull in air than coolant.

I just pulled off the hose from rad cap opening and blew in some pressure, mouth, then held it to see if pressure was lost, it was, hose was cracked, not big but enough for air to be pulled in.

That air should stay at the top of the rad, so wouldn't explain the temp change.

If there is a leak in the engine cooling system then it will leak a bit of coolant but what also happens is that when engine cools down and the coolant shrinks air is sucked in at the leak point instead of coolant via the overflow tank, so no matter how well you air bleed the system more air is being pulled in each drive cycle.

Easiest way to test for a leak is to use a pressure kit, you can rent them.
There is a rad cap fitting with a hand pump and pressure gauge.
You pump up the system to 14-20psi and see if it holds the pressure, if not then a leak is much easier to find on a cold engine with pressure applied, because you can feel around areas that are normally hot, which are the most likely places for an unseen leak, since if they are hot coolant would evaporate fairly quickly not drip on the ground.
Air from this type of leak could cause thumping issues and gauge fluctuations since an air pocket was formed inside the cooling system which would be spread through out the system on start up.

Also with pressure gauge hooked up and pressure applied, disconnect coil pack(no start) and crank engine, similar to Glove test, if pressure gauge fluctuates steadily with engine turning then there is a cylinder leak, and that is what is pumping air into the system.

The coolant has been steady for today. Right where it should be. What happened was I topped off while it was idling but the over flow was empty. Then when it cooled it went down and nothing to suck in. So that's not weird. I've done a pressure test right before putting the water pump and after to check to see if I fixed the leak. It held 16 pounds like normal. I'm hoping idling it on the hill bled that bubble in the core. I'll know this weekend for sure.

 

[cdxhizors]

Ugh so it was thumping this morning when I used defrost. But it was mid 60s all day so I didn't have heat on all day and it was fine. Just when the heater core was on it does it. I don't know what to do from here. Also the front cover seal started leaking today below the harmonic balancer. Both were replaced less than 200 miles ago when I did the timing cover gasket and water pump. Things are going down hill lol. Ranger may have to go back to "project" status not daily driver.