Help! BOILING Coolant Expansion Tank? + leak [SOLVED]

[flapjack]

I've been the owner of a 1990 2.1L VW Multivan for 6 months. As a college student I've loved my van. It's been a dream and have had no issues until now. Last night I noticed after parking and TURNING THE ENGINE OFF, that I was hearing a gurgling / boiling sound from the back. I opened the license plate cover to find this: (turn your audio on)

https://imgur.com/a/p9JojEF

From what I understand this could be a problem with the cooling system / a blown head gasket? The entire cooling system was re-done about a year ago making me think it's probably okay. The temperature gauge reads fine, I don't have any signs of overheating or coolant loss. If you notice in the video the coolant is gurgling to well above the coolant line. I did notice a weird smell that I was unable to identify.

Any idea what this could be? What else should I take a look at to diagnose the issue? I've got my Bentley manual handy...

I have always appreciated advice from you gurus at The Samba.
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1990 Multivan "Sacagawea" [Burgundy]
It's not a slow car, its a fast house.

[Ahwahnee]

What does the other (pressurized) tank look like?

It should be 100% full but I'm guessing it isn't.

[flapjack]

[Vanagon Nut]

[brickster]

Purge air, fill up and pressure test cap and system. Once pressurized, use a bright light to inspect each coolant hose/pipe/connector and address any leaks.

Stay close to home and monitor closely for a while until you know what's happening.
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1984 Campmobile Automatic

[bobbyblack]

If the blue (Blau) cap on the inner tank passes the suck/blow test (look for that here on TS) then I'd get yourself a test kit from a local car place to see if there are exhaust gases in the coolant. Report back on the suck/blow test. Then do the exhaust gas test. Between the two of those we can help you decide where to tiptoe to through the tulips...
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'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[E1]

Tickled to see a lack of doom and gloom today, all good advice above, all from good folks here.

Air in system, blue cap can’t hold it after shutdown when pressures and temperature actually rise for a short time.

Fill overflow, fill expansion (large) tank to very top with coolant, order two (always should have one spare minimum) proper blue caps from a proper bus supplier for now or later, return to worry-free times.

Only fill tank when dead-cold. The level might still rise a lose a little coolant, try to use same type coolant that’s in there, or at least the same color. MUST BE phosphate-free.

The blue cap still might be okay but order two more regardless.

We can discuss handy parts and tools to always have later.

Good Luck!
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[Abscate]

Since you shown your Bus love by naming it , the problem will be minor.
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.ssS!

[Wildthings]

Could just be your pressure cap, which screws onto the pressure tank (VW nomenclature "Expansion Tank". The problem is not likely with the overflow tank (VW nomenclature "Refill Tank").

Over heating can come from many sources, bad or wrong thermostat, clogged radiator, loss of coolant (many possibilities here), bad pressure cap, loose water pump belt, failing water pump, lack of an orifice in the circuit for the rear under seat heater, bad cooling fan or fan switch, failed heat exchangers for the engine oil and/or transmission oil.

About the only failure possible with the refill tank are cracks and a clogged fitting in the bottom where the hose connects. The hose can clog as well from all the gunk that accumulates over time.

Even if you are in college and not flush with funds, it's time to begin the process of eliminating all the plastic parts of the cooling system, with the pressure/expansion tank being a good place to start.

[Vanagon Nut]

[4Gears4Tires]

Everyone should replace their coolant tank with a metal tank. The blue cap is such a stupid failure point to constantly hunt to fix.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[E1]

Dead on correct on blue cap.

I struggle on with plastic, though — mostly because I like to see just what’s going on in there, and there’s been plenty of times I’m glad I could.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[PDXWesty]

[Ahwahnee]

Mine is the original plastic (40 years old) and I am loath to give up the easy visual check.

[kamzcab86]

[E1]

[Howesight]

Since the OP is relatively new to Vanagons and the WBX engine and its cooling system, I thought it would help to point out some of the most common of the many "boiling" causes listed above:

1. Ordinarily, the radiator fan would switch on, even after the engine is shut off, if the coolant was hot enough to cause that "boilover" (for lack of a better word);

2. But there are some reasons that the rad fan might not start as it should. The first possibility is that the area in the radiator that houses the thermo-switch that turns the rad fan on can get gunked up with semi-solid material which insulates the thermo-switch from the heat of the coolant, thus preventing the switch from doing its job. Even in a well-maintained Vanagon, thus can occur within 10 years of a radiator replacement. To check for this cause, with the cooling system cold, simply remove the rad fan switch. Do have something on hand to temporarily plug the fan switch hole to limit coolant loss. You will quickly see if the switch and/or the part of the radiator it lives in is gunked up. If gunked up, then a new radiator is required. Although a crude field "rad flush" can be done to get you home, the "gunking up" in Vanagon radiators is not faxable - - only radiator replacement will do.

3. The rad fan electricals can be quickly checked by connecting the terminals of the rad fan switch connector with a large-gauge piece of copper wire. ( See the Bentley wiring diagram). If the rad fan can be made to run in this way on both its speeds, then no further electrical diagnosis is needed.

4. Even if the rad fan switch is not gunked up, it can fail electrically. You can used a volt-ohm-meter (VOM) to check it in a pot of boiling water, if you suspect it has failed electrically.

5. The high-current fusible link for the rad fan might have failed. See the Bentley manual. However, if that fusible link failed, the most likely cause will be a fan motor that is dying or dead. They don't fail that often in my experience.

6. For whatever reason (sort this later - - don't leave it a mystery) , your coolant system may have excess air in it. In the Vanagon, this can be a serious problem. The system is supposed to bleed itself of air through the expansion tank, but this is not always succesful in a cooling system with some problems. Regardless, at some point in your repair, you are going to have to bleed air out of the system. To do that, raise the rear of the van as high as you can (on a steep slope, or back up onto ramps) so that the expansion tank is the highest point in the cooling system and the coolant at the high (rear) point in the vehicle can force air out of the now-highest point, the radiator bleed valve.

Get access to the bleeder valve on the radiator and bleed the air out. Top up the coolant in the expansion tank as necessary and, once no air is coming out of the radiator bleeder, close that bleed valve. Now you can start the engine and allow the system to come up to operating temperature. Then open the front and rear heaters up to full hot and rev the engine at, say, 2,500 rpm for a minute or two. This forces out any air trapped in the heater cores.

Note that the Vanagon cooling system is very large and very long. This is the reason why it needs a sophisticated (and operating) expansion system and overflow tank. The heat in some pockets inside the engine actally produces small amounts of steam until that steam is again cooled enough to condense back into a liquid water/coolant mix. The expansion tank cap is a critical part in this process. The Vanagon cooling system operates to an extent like a pressure cooker. If the system cannot hold pressure (the maximum pressure, before the pressure tank cap opens and vents, is 15 psi) and the expansion tank cap vents at a lower pressure/temperature (say, 5 psi), then the amount of coolant vented into the overflow tank will exceed the volume of the overflow tank and then spills out of the overflow tank (which is vented to the atmosphere), and you lose coolant.

When the engine and coolant cools, a slight vacuum occurs in the expansion tank which sucks back the coolant in the overflow tank. When all is as designed and functioning properly, the amount left in the overflow tank will be between the "hot" and "cool" lines. That same slight vacuum occurs throughout the cooling system, so any small leaks in the system can allow excess air to be sucked into the system. This is why, even though the system is supposed to be self-bleeding, it often is not - - until you cure all those leaks.
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'86 Syncro Westy SVX

[djkeev]

I will add that the system has way more plastic in it than just that pressure tank with the Blue or Black cap on it.

The potential for failure with 40 year old plastic subjected to heat and pressure is high.

Almost every plastic part is now available in aluminum or stainless steel.
Yes, every piece is expensive but what is a blown engine worth?
The radiator and the heater core still most often have plastic tanks on them.

I forget the sheer number of hoses in the system but I'm guessing about 20-24 depending...... each hose has two ends with a clamp on each.

Personally, to run an aging cooling system that has an unknown service history is simply asking for trouble, trouble that is almost 100% preventable.

If you have engine internal coolant seal problems, that is a horse of another color altogether.

Just be aware of what you have, even Vanagons with engine transplants have as many pipes and hoses, some even more!
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Stop Dead Photo Links how to post photos

Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[4Gears4Tires]

[do.dah]