Bleeding cooling system with seized radiator bleed screw

[1988M5]

This AI stuff is getting annoying. Moderators, this will become a more prevenient issue going forward. One of you guys must be a tech nerd, fix it.

BK
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1991 tin top GL
2002 Winnebago Vista. VW VR6 24V Eurovan front clip powered class C 21' RV.
Some BMWs.

[skills@eurocarsplus]

[zerotofifty]

[DanHoug]

radiators and heater cores are 'thermal precipitators'. meaning, hot solution with dissolved solids enters them, gets cooled and whereby SOME of the dissolved solids drop out of solution due to their reduced solubility in colder fluids. combine that with a reduced flow rate due to the greater area of the coolant tubes vs coolant hose, further exacerbating drop out, and you can see why a radiator is "half full" of schmoo after 40 years. it's a sewage settling pond.

a new radiator is good for engine longevity. half plugged is fine for runs to the local State Park. when you're loaded for a trip, pulling up the 7 mile 5% grade, you gonna want a clean, happy radiator.

as the chemist saying goes... "If you're not part of the solution, you're part of the precipitate."
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[SCM]

[dhaavers]

[wesitarz]

[Van den Broke]

I heated a box end wrench with the propane torch to indirectly apply heat to the hex head but this didn't free it up. I agree that heating is not really practical in this case.

I really like Wesitarz' idea.

I had no idea Malahat Wrecking still had VWs. I remember walking around there decades ago when there was a sea of Beetles, pretty neat (or sad).

[wesitarz]

When I snapped the Nissens plastic screw/bolt I put some JB Marine weld on it then ground it down,cut a slot in the plastic screw/bolt with a dremel and unscrewed it later when I had a replacement bolt.

I replaced the original rad when the bleed screw just spun in place which may be the case here.

[zerotofifty]

[?Waldo?]

If the hoses from engine to radiator are connected properly, (hot from engine into bottom of radiator...) then air does not get trapped in the radiator.

It is normal for the bottom of the radiator to be hotter than the top because the coolant flows from the engine to the bottom of the radiator, to top of radiator, back to the water pump.

If you run the engine at high rpm so the flow from the water pump is sufficient to pull any air with it from the top of the radiator, the air all bleeds out to the pressure tank.

[Van den Broke]

The bottom of the rad was hot, and the top two thirds was about ambient air temperature. Could this still be normal operation (vs. an air pocket), in that the radiator cools that well in the bottom third under light loads?

[jimf909]

Thanks for the explanation. I never understood where all the stuff came from that makes an old radiator so heavy.

[zerotofifty]

Excerpt from link below...

"Vanagon cooling systems are a bit peculiar because the engine is in the back and the radiator is up front. The pipes that run between the two are BELOW both, so if air gets into the system it ends up in the highest point, which is the radiator. If air gets in the radiator it will stay there. There is a bleeder screw on the top of the radiator next to the right headlight used to get the air out. But if air gets back in, it will end up accumulating in the radiator again. "

link...
https://gowesty.com/blogs/article-library/cooling-system-in-vanagons-explained

The radiator is a cross flow type, with both inlet and outlet near bottom, flow is from side to side, trapped air will be in the upper cross flow passages. Air floats over coolant, if air gets into the radiator, it is trapped, thus the bleeder screw is needed to remove trapped air. The water pump cannot suck that trapped air out. Trapped air will remain on the top, unless the bleed screw is used to vent it.

If the air could be pulled out by the pump, then there would be no need for the bleed screw, no need for the factory bleed procedure that uses that screw.

TRAPPED AIR WILL REMAIN TRAPPED UNTIL VENTED FROM THE BLEED SCREW.
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Sorry About That Chief.

Give Peace a Chance.

Words to live by.

[?Waldo?]

I believe that at high rpms, the water pump can push/pull air out of the top of the radiator, but I have neither the time nor the inclination to prove that to anyone. That's not the only thing that GoWesty gets wrong in their articles.

Even though it is possible not to fall off the edge of a balcony even if there isn't a railing, it drastically reduces the risk of falling if there IS a railing. In a similar manner, it is certainly much riskier to run the engine without bleeding the air out of the radiator when filling the system because running the engine with insufficient rpms for the water pump to have the force to remove air from the radiator could easily result in overheating and potential damage. Removing that risk is wise and plenty of reason for the bleed screw at the top of the radiator and for following a good bleeding procedure when filling the system.

[4Gears4Tires]

I have 100% seen the Vanistan heater mod move air bubbles from the top of the radiator. After that air bypass I never had a problem bleeding the coolant system again.
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'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[Van den Broke]

Interesting discussion, I like theoretical as well as experimental approaches to repair issues.

I think if the coolant level in the expansion tank continues to go down for a while with no external (or internal, hopefully) leaks, I can conclude that the air is gradually moving from the radiator to the expansion tank.

[?Waldo?]

Without the Vanistan heater mod I've never had any issues bleeding the system either 'by the book' or with a bong.

If anyone wants to prove for themselves definitively whether or not the water pump has the force to pull air from the top of the radiator, then I imagine the following procedure should do it.

1. Start with a vehicle that has had the coolant system properly bled to ensure that there is not any air in the radiator. This can be easily accomplished (provided your radiator bleed screw is not seized...) by getting the van up to temp, parking on an incline so the right front is high, crack open the bleed screw on the radiator and allow any air to hiss out from the pressure of the cooling system and make sure coolant starts to weep out around the bolt threads. Tighten bleeder and allow the vehicle to cool down to ambient.

2. With the engine cold, open the pressure tank and remove a cup or so of coolant. Save the coolant for later.

3. With a helper watching the pressure tank, open the radiator bleed screw some and have the helper tell you when the pressure tank level has risen back to full. At that point, close the radiator bleed screw and replace pressure tank cap. What you have done at this point is allowed a volume of air into the top of the radiator similar to the volume of coolant that you removed in step 2.

4. Start the engine and let it warm up to normal operating temperature so the thermostat is open.

5. Rev the engine to 4,000 rpms in neutral and hold it there for a minute or two.

6. Go to the pressure tank and see if the level has dropped. If it has, then the reason why is because the air you introduced to the radiator in step 3 has been purged to the expansion tank and you have proven that the water pump has the force to purge air from the top of the radiator.

7. Next, either wait for the engine to cool to ambient and add the coolant that was removed in step 2 back to the pressure tank or add that coolant to the burp tank. Through consequent heat cycles any air remaining in the system will purge from the pressure tank to the burp tank when the engine is hot, and coolant will be pulled from the burp tank back to the pressure tank and refill it when the engine is cools. Check the level in the burp tank with each heat cycle until it does not drop. Top off as necessary.