TheSamba.com :: View topic - Bleeding cooling system with seized radiator bleed screw

Mon Jun 30, 2025 2:11 pm

Hi all,

I am hoping to bleed out the air from my '89 Vanagon but discovered that a previous knucklehead installed a plain steel hex head cap screw in the radiator instead of the correct bleeder screw.
It will not unscrew with a medium amount of torque and I don't want to force it as I think it may well break the brittle plastic it's screwed into.

Any tips on how to bleed the system, or to get this sucker out?
Thanks.

It's a Subaru conversion, if it matters.

Mon Jun 30, 2025 3:40 pm

Just to the left of the bleed screw, in the black plastic is a round embossed emblem.
Read the 2 digit number in the center of it.
That is the year the radiator was made.
If the same or earlier year as your van then consider what might happen soon anyway.

Mark

Mon Jun 30, 2025 3:47 pm

Are you sure it isn’t a bleed bolt? It looks stock to me. Anyhow, I believe there is a brass insert for threads not plastic. Maybe some PB blaster and some patience and it will free up.

I agree with Mark, that a new radiator might be a better option. It’s important to have that ability. There are likely some ways to get the air out, but not worth the risk.

Mon Jun 30, 2025 4:33 pm

Earlier Nissens rads had a plastic screw/bolt that easily snapped off. They supply a metal one now. I replaced mine with a SS bolt. Lots of PB Blaster?
Bleed it by running it hot and parking it with raised rear end (slope or ramps). Any air will collect in the expansion tank as it cools.
Edit: there should be an O-ring with the rad bolt.

Mon Jun 30, 2025 4:54 pm

Well I just assumed (haha) that the original bleeder bolt would not be made of steel that would obviously rust.

Maybe it is the correct screw. It has a 13mm hex and has the raised script ESKA 88.

The date code circle shows 88. So it looks like the original radiator.
I am not going to pre-emptively replace a good, 37 year old radiator with a POS aftermarket one that may last one tenth to one quarter that long, from what I've read about them on this site.

Well there is a $1000 USD all aluminum unit but I'll pass.

In my experience these plastic / aluminum radiators start to leak slowly and don't fail catastrophically. So I'll wait.
With luck it will get a tiny leak at the very top, allowing air to be bled out while only losing a few drops of coolant a week.

Mon Jun 30, 2025 4:57 pm

After 40 years your original radiator is guaranteed to be filled with sludge. PB Blast it, try to get the screw off, but if it snaps, it snaps. It's time to replace it anyway.

Mon Jun 30, 2025 5:09 pm

Well what you got there is galvanic corrosion, the screw should be brass, but since it is steel, well it galvanicly corroded given that it is screwed into brass.
High heat aint an option for you given the plastic near by.

So try the penetrating oils, Kroil, PB Power Blaster and such. You may need days of soaking.
Then keep a trying to loosen it.

If that fails, remove the radiator for access and try to drill the bolt out, with the right drills, technique and a steady hand that can work.

Replace with a brass screw to prevent reoccurance of corrosion.

Mon Jun 30, 2025 5:15 pm

4Gears4Tires wrote: After 40 years your original radiator is guaranteed to be filled with sludge.
Agree. I have pulled apart a half dozen original radiators and they all were filled with sludge no matter how nice they looked.

Mon Jun 30, 2025 6:32 pm

Van den Broke wrote: The date code circle shows 88. So it looks like the original radiator.

First, I read about an '87 Golf Cabriolet still sporting its original K-Jetronic fuel accumulator, now ^this! :shock:

As with that accumulator fellow, I agree with the others and say, "Replace it!" Not a matter of if, but when it will fail. I just flushed my cooling system a couple months ago. The crap that came out of my approx. 10–12-year-old radiator was astounding. Hate to see what's inside a 40-year-old radiator! :-&

Mon Jun 30, 2025 6:38 pm

wesitarz wrote: Earlier Nissens rads had a plastic screw/bolt that easily snapped off. They supply a metal one now. I replaced mine with a SS bolt. Lots of PB Blaster?
Bleed it by running it hot and parking it with raised rear end (slope or ramps). Any air will collect in the expansion tank as it cools.
Edit: there should be an O-ring with the rad bolt.

No O-ring on my 1986 Van, it has a brass bolt and a soft copper gasket for the seal. There is no groove for an oring. With no o-ring groove, an o-ring is at risk of failure.

Use a soft ( annealed) copper gasket for the seal. and a brass bolt so in as it wont under go galvanic corrosion as is the case with the steel bolt which is the subject of this thread

Mon Jun 30, 2025 10:16 pm

"Replace it!" Not a matter of if, but when it will fail."

But isn't that true with a new radiator as well, considering the low quality they are now?
The current original radiator will last, maybe another five years.
A new one might last, maybe five years. What's the point?

I've applied penetrating oil to the bolt but am not optimistic about it coming out. But I'll keep gently trying. Drilling it out is certainly an option, but of course I'd rather not remove the radiator.

However, if I do throw in the towel and buy a new radiator, can you fellows suggest a better one?

Tue Jul 01, 2025 1:26 am

The Nissens I put in has been going for 10 years plus. They are not cheap anymore ($250 then). It had a plastic bleed screw with an O-ring. I replaced it with a SS metric bolt with a bleed channel cut into it. The Nissens is $399 from autopartsway.ca. Can try werke1 out of Vancouver to import one in from a US vendor.

Try germanparts.ca They have a Mahle rad:

https://germanparts.ca/parts/volkswagen/1988/vanagon/2.1-l-2109-cc-h4/gl/engine-cooling/radiator/

Tue Jul 01, 2025 2:48 am

I would warm it with a torch with a needle tip three time, using my fingers to keep it well under plastic melt temp.

The get a socket on it and off it will pop.

Worst case if it breaks or melts, JB Weld in a stopcock and bleed from there.

A lot of keybaord warriors here will spend your money for you - no need to throw away an old radiator, especially if you use a run to fail model for parts. There are choices, not single right answers, for every repair.

Tue Jul 01, 2025 6:27 am

I think it was a Behr brand radiator that I installed in my van 12 or 13 years ago. It still works.

Don’t let all the talk of “new but potentially poorer quality” parts scare you into running a time-bomb of a 40 year old wear item.

Tue Jul 01, 2025 8:57 am

A 37-year-old radiator has long outlived its designed service life. Unless all owners of the van have religiously changed the coolant every 2 years, then it is undoubtedly filled with scale and does not dissipate heat anywhere near as well as a new unit.

If the radiator still cools adequately in the most extreme loads in high ambient heat, then I probably wouldn't replace it preemptively, but I would feel completely unconcerned about breaking that bleeder bolt/radiator because if it did break it would just make the decision to replace the radiator completely clearcut.

Tue Jul 01, 2025 10:26 am

You can also try tapping that bolt with a light hammer about 200 times and see if that can loosen the scale enough to allow you to turn it out. Good luck.

Tue Jul 01, 2025 11:05 am

The fix is simple, crack that bolt loose. If it breaks and becomes useless, go to a hardware store and find the old guy with grey/white hair. He will hook you up with epoxy and a valve.

BK

Tue Jul 01, 2025 12:09 pm

Van den Broke wrote: "Replace it!" Not a matter of if, but when it will fail."

But isn't that true with a new radiator as well, considering the low quality they are now?
The current original radiator will last, maybe another five years.
A new one might last, maybe five years. What's the point?

ok, then don't open the bleeder and cook the engine. there, now the fucking 800 year old radiator will never leak. problem solved.

you're lucky to get 5-7 years out of ANY cooling system made in the last 15-18 years. it's time is up, or you can sit around and waste time and not be enjoying the van or toss a new radiator in it when you pull the brass insert out of the ancient heat cycled plastic. your call

fuck, I hate posts like this. like what are you going to do, waste a week+ trying different things just to have it break anyway?

Tue Jul 01, 2025 12:14 pm

Thanks for all the suggestions.

The drilling idea got me thinking - I could drill a small hole in the bolt and thread it for, say, a 3mm (stainless!) screw to bleed it.
If I were really lucky I could loosen the radiator and tip it forwards at the top so I could do the job without having to remove it.

When the van is warmed up the radiator is only hot on the lower third, which seems to indicate that's the coolant level. In other words I have one third the cooling potential of a properly functioning system.
But the climate here is not too hot so it's been okay for the few years of ownership.

I did try putting a 13mm box wrench on the bolt and tapping it many many times with a big brass bolt, I will also try the suggestion of heating the bolt gently while shielding the rad.

Cost is an issue, the only way my family afforded this beast was by squandering a small inheritance to pay for it. Luckily I can do all the repairs and maintenance myself, so far.

Before this the most expensive vehicle we ever bought was $3500.

Tue Jul 01, 2025 12:17 pm

Hey, thanks for the input, Skills.
Don't hate, just be amused.