Unsolvable airlock? Cooling system issue on AHU TDI JX style 50°

[ALIKA T3]

Aloha everyone!

Grab a beer that`s gonna be a long one to solve...

I`m battling cooling flow issues to the radiator not even 10 days before shipping my van to CA to finally do my dream trip with the Syncro to Central America.

Well, looks like it won`t happen on time now...

If you can help me, that would be awesome. There is clearly something I must be missing somewhere but I`m too stupid to find out what.

So, here`s the deal:

Brand new rebuilt 1.9 Tdi engine by yours truly over a period of 8 years. Finally got on the road, kinda...

JX 1.6 TD style layout.

I cannot bleed the air out of the engine hot hose (the spider hose). When the engine is off, if I squeeze hoses fast, I can hear bubbles in there.

Let me tell you that`s not my first rodeo with diesel engines or Vanagons in general, and I had never had this issue, ever, so I`m really at loss here....

I always bled the engines nose down , expansion tank open, heater loop open, and that`s it. Easy as it gets.

I tried also nose up to move air a bit and while accelerating to avoid sucking air into the radiator.

So far I have almost no flow to the radiator, I can bleed it easily, but the stainless pipes underneath tell me the flow is almost non existent.
The hot pipe after a while get extremely hot on the top of its diameter and warm on the bottom, indicating coolant is barely moving in there.
So I put a brand new Behr of RSA radiator, just in case ( old one was a copper core AKG radiator from 1984, with 17,000 original miles so I had kept it).
Same result.

I replaced the brand new 80*c thermostat ( Wahler brand, made in France) by an 87*c thermostat ( Vernet brand, also made in France).
No improvement.

I ordered an original 87*c VW thermostat ( prolly made by Behr in Czek republic, manufacturer code BCH )
The thermostat arms are oriented vertical at 12 and 6 o`clock as to not interfere with the flow from the lower hose from the expansion tank.

I also spoke to my buddy Felix in Germany who pointed out I had aftermarket silicone hoses and most likely missing the restrictor into the hose that goes to the upper expansion tank nipple. I remembered about this but actually didn`t think much about it. So basically, this 4mm restrictor hose makes sure the coolant flow doesn`t take the path of least resistance by-passing the radiator loop. http://www.t3-pedia.de/index.php?title=K%C3%BChlsystem_bef%C3%BCllen_und_entl%C3%BCften

Genius, right?
I took a 1/2 square drive socket extension, cut it and drilled a 4mm hole in the center and shoved it into the hose, added a clamp.
It made an improvement in how fast I could bleed.
I thought that was it but nope...

I had a dual oil heat exchanger set up, one exchanger is just a bigger one for the engine, the other was for warming up a possible veggie oil set up at the fuel filter. I thought it was trapping air, so I was, eff it, go back to stock set up, only the engine oil heat exchanger.
I do not know which way it circulates in there but from touching hoses, it seems like the cold gets sucked in the cooler and goes out into the hot hose then back to radiator.

My heater loop works like a charm, so the water pump must be working. It is a cast impeller water pump made by Graf from what I recall. The pump runs clockwise from the V-belt exactly like from factory. Correct size pulleys down to the part number, correct impeller angle ( in case there was a CCW running pump option out there).

I tried pinching the culprit hose to avoid by-passing the radiator completely and force things to and from the radiator.

I need to do that next on the heat exchanger loop but I doubt it`s gonna make a difference, I mean in what world do you have to do that to bleed a diesel? This is becoming ridiculous.



I tried the bong method, which I had never needed until now. I used on flat surface and in a slope, nose down. No improvement.

I took all hoses to and from the radiator to blast the garden hose through them to dislodge any potential plug that may have been in there ( unlikely, but out of desperation...)

I made a special additional coolant tank pressurized to bleed things and crack open hose clamps at the oil heat exchanger connections to get air out. No improvement.

I removed the extra cooling hoses to the fuel heat exchanger that was in series. No improvement.

Here`s the cooling diagram, I must have checked it out a million times hoping I made a mistake, but nope...

Here`s a real life view of the radiator connections

The water pump left nipple ( top right on the picture here) goes to the cylinder head flange between the injectors. This hose gets closed when the thermostat opens. The gap is about 5mm.
The right nipple is the one from the bottom of the expansion tank, so you can understand without the restrictor on the top hose at the expansion tank it would by-pass the radiator completely. This port is always open fully.

The cold IN from the radiator is completely shut until the thermostat opens.

So far, I still have air in the engine hoses, unbelievable.
Either it`s creating an air lock and the flow is dead to the radiator as a result or something is not right with the flow from the beginning so I can`t get these bubbles to move out of there since the flow is weak.
Chicken and the egg story.

I checked the impeller, it is not loose from the shaft.

This sh!t`s been killing me, I must have spent over 50 hours on this. I`m dead.

EDIT: I also checked for combustion leaks just in case. Liquid stays blue ...
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[djkeev]

Sorry, I don't know diesels at all.

But I do offer my heartfelt condolences and encouragement.

Maybe get a buddy to cone look, sometimes fresh minds and new eyes see the obvious.

Dave
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[MarkWard]

Three tips. The thermostat is clocked wrong. You want the tabs out of the flow. I always drill an 1/8” hole in the thermostat to ensure you have coolant on both sides of the thermostat. Last tip, I always fill the engine through the top hose on the cylinder head. Then I fill the cooling system. Don’t imagine the order matters. Then bleed as usual.
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[Steve M.]

The 1/8" hole in the thremostat disc also lets air through it when bleeding, but I've got the feeling you know this already.

My brain is getting dizzy looking at all the hoses! That's a lot of work -looks like a great job getting it all in there.
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[uberaudi]

Have you boiled your thermostat to see if it actually opens? There is always the chance of brand new faulty parts. Like Mark said, drilling a small hole in it ensures flow on both sides and if I remember right, older Audis always had a hole in their thermostats.

I had a heck of a time bleeding my 50 degree and ended up having the best luck with parking on a steep hill, nose up, and cracking the radiator bleeder bolt. It's been smooth sailing since.
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'84 Adventurewagen 1Z Tdi, '89 Tintop ABA, and a 86 Syncro tintop WBX.

[valvecovergasket]

If you have access to a larger air compressor (20-30gal) I'd recommend trying one of the vacuum bleeders. We've had really good luck with them on a couple vans and it does the work of checking for leaks prior to filling as well.
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[skills@eurocarsplus]

since we're playing take a guess....

we've all been there. couple of things to consider:

-did you mix up any hose routing?

-did you leave a rag/plastic plug/tape etc in a hose or over a coolant port?

new doesn't = good as we all know. was the water pump impeller made correctly, or is it slipping on the shaft? yes...i have seen both of those happen

i will think about any other crazy situations i have seen and add as they come to mind
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[old_man]

Are you positive you still have air? Is your TDI overheating? Reason I ask is I have found the TDI to be rather efficient. It does not make a lot of heat especially in cool weather unless your are giving it on the highway.

[Vanagon Nut]

This is counter intuitive but.....

crack in cooling system part allowing air in as engine cools?

Have you measured temps at various engine parts?

I see the GW tool but have you measured cooling system pressure? i.e. does system maintain pressure?

Neil.
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1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[?Waldo?]

As a restrictor in the upper expansion tank hose, I use a fender washer with the appropriate OD and ID. Cheap, easy, and effective.

The only symptom is air in the system. The limited flow to the radiator sounds like the thermostat simply hasn't opened. With a TDI that can take some effort. How much have you run it?

I find these to be remarkably easy to bleed. I use the libby bong for initial bleeding and then when fully up to temp I park with the passenger front side higher and open the bleeder on the radiator. I do that a couple/few times until coolant immediately comes out (no air). I then just top off the expansion tank before each cold start until no air is present there and keep the license plate tank at the appropriate level.

If air is continuing to get into the engine after that point, then you have a leak in the cooling system somewhere.

[ALIKA T3]

[ALIKA T3]

[ALIKA T3]

[ALIKA T3]

[ALIKA T3]

[skills@eurocarsplus]

have you tried, while warm and under pressure to just barely crack open the offending hose?

do it slow and carefully. i have a tractor that is a fucking bitch to bleed. what i do is get it warm, cap on so pressure is built. loosen the hose clamp just enough to get a hose pick tool in there.

once i get a good few psssshhhhh of air coolant generally follows. after i'm happy with the amount of coolant that puked it's usually good to go.

you may just need the pump to catch a good prime
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[?Waldo?]

[ALIKA T3]

[ALIKA T3]

[syncroserge]

I think you have 2 things adding up to trouble..

1. air in the block from fresh rebuild,

2. it's a TDI..

I use external heat to start/bleed fresh filled diesels. Coolant block heater, oil pan heater, Espar hydronic..

Being in Hawaii you might not have any of those but anything will do..heat gun even..

I bet nothing's wrong with the engine, hoses, themostat etc..

Get the block as warm as you can artificially...