Coolant Hard Line Behind T-stat Housing, ?'s

KrashDH · Aug 13, 2018

For those that have had the pleasure of replacing the o-ring at the end of the hard line that enters into the block, I have a quick couple of questions.

I chased down a leak at the plastic t-stat housing, so that and the t-stat are new, and it's not leaking. It's dry around there.

I literally just flushed the coolant when I did my TB job (a month ago or so) so it's nice n pink (and VW coolant isn't cheap).

The hard line connection is leaking, I can see where it's pooling just below the hard line on the upper rib and then leaking down onto the lower ribs. It's a slow leak, but it's wet behind there.

So my questions.
With the t-stat replacement, I was able to just remove that hose and let a bit of coolant drain from there. I didn't need to drain the whole system to replace that housing and t-stat.

I see with the hard coolant line that there are a couple of coolant hoses coming off of it. It's up pretty high, so can I get away with just draining the coolant from the hard line so I can avoid doing an entire coolant change? Or is this one an all-or-nothing?

Also, I know the oil feed line at the filter housing needs to come off. I suppose I just need to draw the oil out of there prior to removing this?

Hopefully it won't fight me too bad, the car isn't in a rust environment.

Thanks all in advance.

AndyBees · Aug 13, 2018

The hard line (painted black metal pipe) is the "return" coolant from the: oil cooler, expansion tank, EGR cooling system and heater. It is about on the same level as the center of the T-stat opening.

So, considering that metal pipe is in a very tight location, you're going to lose a considerable amount of coolant when you loosen the "bolt" that holds it down and pull the pipe out. Even on my ALH in the Vanagon, which due to modifications, does not have all those hoses attached to it, coolant loss will happen. Also, the hose going off the tee on the metal pipe to the bottom of the coolant expansion tank has to be removed in order to rotate the metal pipe and slide it back far enough to have access to the O-ring. The Dip Stick Tube and it's metal pipe coming up from the bottom is the issue there.

This is what I do to minimize loss of coolant ........... vacuum the coolant out of the expansion tank. Coolant will keep draining into the expansion tank until no more will come out. At that point, you can remove one or more of the hoses (EGR coolant hose or heater hose) to insert vacuum source to remove more coolant. Then, vacuum more from the bottom of the expansion tank.

My vacuum source is made from an old vacuum pump attached to a plastic weed killer spray canister. I use the 5mm braided hose with a short piece of plastic pipe on the end of it. I can reach into those small pipes and vacuum out the coolant. Works great and I am able to do changes with very little loss of coolant.

Seems you may have to unplug the wiring connector that goes to the Injection Pump to allow more working room with the metal hard pipe. I think you can pull and rotate the metal pipe far enough to replace the O-ring without totally removing it.

When I was doing my ALH engine in the Vanagon, I had that pipe in and out numerous times. Vaseline worked great and it does not leak with the OE O-ring still in use after all those times being in and out.

Hope this helps.

WildChild80 · Aug 13, 2018

This is why I am addressing that o-ring prior to engine install...it looks like a pita

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KrashDH · Aug 13, 2018

AndyBees said:
The hard line (painted black metal pipe) is the "return" coolant from the: oil cooler, expansion tank, EGR cooling system and heater. It is about on the same level as the center of the T-stat opening.

So, considering that metal pipe is in a very tight location, you're going to lose a considerable amount of coolant when you loosen the "bolt" that holds it down and pull the pipe out. Even on my ALH in the Vanagon, which due to modifications, does not have all those hoses attached to it, coolant loss will happen. Also, the hose going off the tee on the metal pipe to the bottom of the coolant expansion tank has to be removed in order to rotate the metal pipe and slide it back far enough to have access to the O-ring. The Dip Stick Tube and it's metal pipe coming up from the bottom is the issue there.

This is what I do to minimize loss of coolant ........... vacuum the coolant out of the expansion tank. Coolant will keep draining into the expansion tank until no more will come out. At that point, you can remove one or more of the hoses (EGR coolant hose or heater hose) to insert vacuum source to remove more coolant. Then, vacuum more from the bottom of the expansion tank.

My vacuum source is made from an old vacuum pump attached to a plastic weed killer spray canister. I use the 5mm braided hose with a short piece of plastic pipe on the end of it. I can reach into those small pipes and vacuum out the coolant. Works great and I am able to do changes with very little loss of coolant.

Seems you may have to unplug the wiring connector that goes to the Injection Pump to allow more working room with the metal hard pipe. I think you can pull and rotate the metal pipe far enough to replace the O-ring without totally removing it.

When I was doing my ALH engine in the Vanagon, I had that pipe in and out numerous times. Vaseline worked great and it does not leak with the OE O-ring still in use after all those times being in and out.

Hope this helps.

Thanks for all the info Andy. Yeah I knew I was going to lose coolant, was just trying to figure out the most efficient way to do it.

I was thinking if I could clamp the expansion tank and oil cooler hoses off close to where they meet the hard pipe( @ number 17 and no number), that when I removed them, the coolant in the upper part would drain right out of the hard pipe. not even sure I could get anything in there to direct coolant flow. But that in theory would drain everything out of what I needed to work on up top there and keep me from having to break the connections down by the oil cooler and expansion tank.

If I don't have room to do that, looks like I'll be doing a good ole fashioned drain all over again via the expansion tank then the cooler lines. I hate doing stuff twice (or 3x now, partial drain to replace the t-stat and housing prior to TB job...)

But yeah I plan on removing all the brackets and wiring that I need to free the hard pipe, as well as that oil feed line from the housing. That in theory should give me enough wiggle room to yank that thing horizontal. Oh and possibly the air box too. All to replace part number 3...

I'll be putting a smidge of RTV where the hard faces of the engine and pipe meet as well after I get everything cleaned up.

AndyBees · Aug 13, 2018

Clamping off the hoses will help, but the coolant on the "other side" of the circulation scheme will back-flow through the head down into the Water Pump housing, although probably slow.

For what it is worth, in the drawing, #17 is an Error. The coolant flows in the other direction. That is from the bottom of the expansion tank! Bentley made a mistake there which I caught back in 2012 when working with the ALH install in my Vanagon.

You should look into making or purchasing some sort of vacuum system. It makes this sort of job much less messy.

EDIT: Yeah, I forgot about the hard oil feed pipe to the Turbo. If you can work around it, that would be the best decision. Loosening the banjo nut at the oil filter housing will be easy, but the brace on the back of the block and the connection at the top of the Turbo will not be fun. And, for what it is worth, I've had that pipe off the ALH engine in Vanagon numerous times and re-used it each time with no leaks. Seems the Oil Filter Housing will keep oozing oil when the banjo fitting is removed... so, that'll be a mess to deal with.

KrashDH · Aug 13, 2018

AndyBees said:
Clamping off the hoses will help, but the coolant on the "other side" of the circulation scheme will back-flow through the head down into the Water Pump housing, although probably slow.

For what it is worth, in the drawing, #17 is an Error. The coolant flows in the other direction. That is from the bottom of the expansion tank! Bentley made a mistake there which I caught back in 2012 when working with the ALH install in my Vanagon.

You should look into making or purchasing some sort of vacuum system. It makes this sort of job much less messy.

EDIT: Yeah, I forgot about the hard oil feed pipe to the Turbo. If you can work around it, that would be the best decision. Loosening the banjo nut at the oil filter housing will be easy, but the brace on the back of the block and the connection at the top of the Turbo will not be fun. And, for what it is worth, I've had that pipe off the ALH engine in Vanagon numerous times and re-used it each time with no leaks. Seems the Oil Filter Housing will keep oozing oil when the banjo fitting is removed... so, that'll be a mess to deal with.

I don't think you can work around that oil feed line, but I think you can flex it with it disconnected only at the oil filter housing. I seem to have read it's not necessary to remove it from the turbo.

My plan was to suck the oil out of the filter housing to mitigate the leaking at that fitting. It can't really keep leaking once that is drained I'm assuming? Maybe I can find the right fitting to temporarily plug it after I remove the banjo. I'll let the car sit overnight before I attempt any of this, it will help a bit.

I'm guessing in my case then it's just probably the easiest to drain the expansion tank, pull the lower radiator hose and oil cooler hose from the hard pipe, and let all that drain. That should be enough for me to get what is needed out of the system for this. I'm dreading this repair

I didn't take that arrow in the photo above as coolant flow, I just thought it was a number telling where it connected to.

KrashDH · Aug 13, 2018

Looks like I just stumbled upon this post.

http://forums.tdiclub.com/showpost.php?p=2493103&postcount=41

No photos, but good description.

I think I'd rather do a TB job over again than this one haha.

Edit:

Here's another great write up of someone that fully removed it:

http://forums.tdiclub.com/showpost.php?p=3604915&postcount=8

Maybe I'll do a full write-up when I can get after this

KrashDH · Aug 13, 2018

Any reason this line, other than having a multitude of brackets connected to it, be fabbed up from some coolant lines with inline "T's" that go to the respective components? Ie could you just keep the hard nub that enters the block and fab up the rest of it from regular line? If this is a return line from components, I can't imagine that it sees high pressures at all??

Maybe it's because of the length? I would think you could add some coolant hose supports where it bolts to the engine just because.

Not that I would do such a thing...

oilhammer · Aug 13, 2018

You are WAY overthinking this, LOL. This is not *that* hard of a job, it is actually easier on the diesels than it is on the gassers due to how they changed the way the pipe mounts, even though there is no good reason why it should be any different. That's Volkswagen.

Depending on its condition, I often remove the pipe completely from the car, clean it up and paint (clear) the whole thing, and wire wheel the o-ring land. On older cars I try and update to the newer style with the double lip o-ring. Your car should already have the new style pipe.

You are going to lose a substantial chunk of coolant. It is not that expensive. Get it from someplace other than the dealer if your wallet flinches.

I take the oil pressure switch loose, and feed the wire harness up and out of the way completely, lay it off to the side toward the battery.

Good time to reseal (manual) or replace (automatic) the flange at the head, too.

KrashDH · Aug 13, 2018

oilhammer said:
You are WAY overthinking this, LOL. This is not *that* hard of a job, it is actually easier on the diesels than it is on the gassers due to how they changed the way the pipe mounts, even though there is no good reason why it should be any different. That's Volkswagen.
Depending on its condition, I often remove the pipe completely from the car, clean it up and paint (clear) the whole thing, and wire wheel the o-ring land. On older cars I try and update to the newer style with the double lip o-ring. Your car should already have the new style pipe.
You are going to lose a substantial chunk of coolant. It is not that expensive. Get it from someplace other than the dealer if your wallet flinches.
I take the oil pressure switch loose, and feed the wire harness up and out of the way completely, lay it off to the side toward the battery.
Good time to reseal (manual) or replace (automatic) the flange at the head, too.

Thanks Hammer.

My car is rust free for the most part, that hard line isn't bad and doesn't show signs of rust, but I may pull it via link #2 I posted above just to get it out and paint it.

I ordered the seal and coolant flange o ring and copper washers (as well as another jug of coolant) from IDparts.

You mentioned an updated double lip o-ring? Is that different than the square o-ring that I ordered from IDparts?
Yeah I think I'm going to go the route of post link #2 that I showed above

I know coolant isn't expensive, but this is the 3rd time this summer I've had to do a coolant change in the car. Way more than I want to. Literally the last time was a few weeks ago during my TB procedure.

You said you take the oil pressure switch loose? does that mean you remove the switch completely or just move the wiring out of the way?

oilhammer · Aug 13, 2018

I call it a double lip, you'll see when you get it. It does not look like a conventional o-ring. I think the change happened around 2000 or so, can't remember, but it is a different pipe, too.

Yes, I take the switch completely out, seems like I end up having to swing the pipe up right where or very near the switch, and would rather not risk breaking it.

Just take your time and remove everything that is in the way. A lot of steps, but none of them are particularly hard. Just a time consuming fiddly job is all.

FWIW, often times with cooling systems, when one leak is fixed, then another happens. It is because that second one was "just ready" to leak, but never was asked to hold back enough pressure to leak because the first one was doing that.

Luckily, the ALH is a rather simple engine, with a rather simple cooling system, that doesn't have that many places to leak in the first place. If you have not done so already, another common spot is the quick connect flanges at the heater core. There is an o-ring inside that degrades over time.

AndyBees · Aug 13, 2018

I agree with Oilhammer. (but, easy for him to say considering he does this stuff while he sleeps....

)

Since that coolant isn't available in my neck of the woods, I always try to capture all that I can when doing anything involving the possibility of coolant loss. And, when vendors run specials such as, free shipping, free shipping on large orders, etc., I always buy at least one gallon of the pink stuff.... it never goes bad.

As for the hard oil pipe to the Turbo, it does have a "brace" which is bolted near the end of the head below the coolant flange. To obtain much flexibility, you'll have to loosen up or remove that brace.

KrashDH · Aug 13, 2018

oilhammer said:
I call it a double lip, you'll see when you get it. It does not look like a conventional o-ring. I think the change happened around 2000 or so, can't remember, but it is a different pipe, too.
Yes, I take the switch completely out, seems like I end up having to swing the pipe up right where or very near the switch, and would rather not risk breaking it.
Just take your time and remove everything that is in the way. A lot of steps, but none of them are particularly hard. Just a time consuming fiddly job is all.
FWIW, often times with cooling systems, when one leak is fixed, then another happens. It is because that second one was "just ready" to leak, but never was asked to hold back enough pressure to leak because the first one was doing that.
Luckily, the ALH is a rather simple engine, with a rather simple cooling system, that doesn't have that many places to leak in the first place. If you have not done so already, another common spot is the quick connect flanges at the heater core. There is an o-ring inside that degrades over time.

Ah I see upon looking closer yea there is a dual lip kind of there.
Very well could be that one sprung because sealing up the t-stat housing (new) added some pressure the system hadn't seen in a while. Or they were both leaking and I couldn't see that one at the time and had pinpointed the culprit to be the t-stat housing to block interface

AndyBees said:
I agree with Oilhammer. (but, easy for him to say considering he does this stuff while he sleeps.... )

Since that coolant isn't available in my neck of the woods, I always try to capture all that I can when doing anything involving the possibility of coolant loss. And, when vendors run specials such as, free shipping, free shipping on large orders, etc., I always buy at least one gallon of the pink stuff.... it never goes bad.

As for the hard oil pipe to the Turbo, it does have a "brace" which is bolted near the end of the head below the coolant flange. To obtain much flexibility, you'll have to loosen up or remove that brace.

Yeah I read about getting to that brace by moving the intake pipe. I thing there's one on the back of the head too I may have to loosen?

I was on IDparts this morning, and I had the coolant and 2 seals in my basket, went to check out, and shipping was $20 on a $24 order I was like what the heck? I realized I had forgot the copper crush washers so I went back and put them in the basket, and now I had a shipping option that was $5...not sure what that was all about. Oh well it's on the way, another thing to get to when I manufacture a longer day or week...

Appreciate the help guys, maybe I'll do a dedicated writeup with photos

AndyBees · Aug 13, 2018

I have a below dash mounted pressure gauge for the cooling system. I've never seen pressure above 9 lbs. Generally, pressure hangs around 7.5 lbs. But, some coolant loss, combined with a very hot day in stop and go traffic and pressure can climb fast.

gmenounos · Nov 11, 2019

oilhammer said:
On older cars I try and update to the newer style with the double lip o-ring.

What's involved with updating to the new style? Just buy the newer style pipe and o-ring? My 99.5 Golf is leaking and I was going to replace the pipe anyway since it's pretty rusty. Looks like the old pipe (038-121-065-AM) was recently discontinued.

Nero Morg · Nov 11, 2019

gmenounos said:
What's involved with updating to the new style? Just buy the newer style pipe and o-ring? My 99.5 Golf is leaking and I was going to replace the pipe anyway since it's pretty rusty. Looks like the old pipe (038-121-065-AM) was recently discontinued.

Yes, just new pipe and o ring. Mounting locations are the same, just make sure you get one for an auto or manual.

oilhammer · Nov 12, 2019

The mountings are NOT the same.

Here is how it went:

early ALHs had one style, then they "updated" this style with the newer double lip o-ring, but it still mounts the same way.

Then the later cars used a different pipe, that not only had the double lip o-ring, but had different mounting points.

The update for the early cars is no longer available. So you'd have to get the later type pipe and mounting hardware to make it work. The threaded holes are in the block already, HOWEVER, they've never been used, were exposed naked cast iron, so will be rusty. You will need a thread chaser (not a tap) to clean them out. And there are a couple different sizes. The one at the front is a M7x1.00, the one at the rear is I think M10x1.50 but not 100% sure.

Also, for anyone reading this, while there were three versions of this pipe (early, updated early, late), there are also several versions of each depending on equipment. The manual trans is different than the automatic (auto cars have an extra nipple for the hose to the ATF cooler), and the New Beetle is different because the angle of the nipple going to the hose to the water bottle is UP instead of DOWN like it is on the G/J.

Nero Morg · Nov 12, 2019

oilhammer said:
The mountings are NOT the same.

Interesting. Just speaking from experience, I put a 2003 pipe on my 2000 engine, and it bolted right up. So I guess I should have said, hey, holes are there, good luck with rusty threads?

oilhammer · Nov 12, 2019

1998 and 1999 cars are the early type mounting. 2000s could be either, depending on production/plant/etc.

Chances are your 2000 engine had the later type to begin with (most did).

VAG (and others) do middle year changes pretty regularly, so you have to watch out for those things.

The ALH's block changed some time in 2002 as well, they went to a thicker boss on the spot where the mounting bracket attaches.

What adds confusion to the issue is the fact that for the USA and Canada, ALH powered cars could have come from one of three different final assembly plants, and they may not have gotten the newest engine bits at the same time, even though the engines themselves may have all come from the same place.

Plus, ETKA's VIN and production date clues are not 100% correct. Good news is, VAG puts part numbers on just about every last little bit on the car, which is helpful.

gmenounos · Nov 12, 2019

oilhammer said:
The mountings are NOT the same.
Here is how it went:
early ALHs had one style, then they "updated" this style with the newer double lip o-ring, but it still mounts the same way.
Then the later cars used a different pipe, that not only had the double lip o-ring, but had different mounting points.
The update for the early cars is no longer available. So you'd have to get the later type pipe and mounting hardware to make it work. The threaded holes are in the block already, HOWEVER, they've never been used, were exposed naked cast iron, so will be rusty. You will need a thread chaser (not a tap) to clean them out. And there are a couple different sizes. The one at the front is a M7x1.00, the one at the rear is I think M10x1.50 but not 100% sure.
Also, for anyone reading this, while there were three versions of this pipe (early, updated early, late), there are also several versions of each depending on equipment. The manual trans is different than the automatic (auto cars have an extra nipple for the hose to the ATF cooler), and the New Beetle is different because the angle of the nipple going to the hose to the water bottle is UP instead of DOWN like it is on the G/J.

Thanks! It turns out that when I first spotted the leak almost a YEAR ago

, I ordered both the old (038-121-065-AM) and new (038-121-065-Q) pipes (manual transmission) and a couple each of the old (WHT-006-407) and new (06B-121-687) o-rings. The pipe in the 99.5 Golf looked very rusty and the '01 wagon ('03 engine) is of similar age and they use plenty of salt on the roads here, so I figured it would be good to have a spare for the wagon. Little did I know that the old style would be NLA within a year, so I got lucky ordering one when I did.

Tonight I took a close look at both replacement pipes and they both use the newer style flat o-ring. I then looked in an old version of ETKA that I have and couldn't even find the part number for the pipe that uses the old style o-ring. Did they change the design of the pipe end without changing the part number?

oilhammer · Nov 13, 2019

No it is a different part number.

For some reason, ETKA no longer shows the original (single lip o-ring) style pipe, they just show the updated version, with the tag "also use..." and the later style o-ring listed. Then they show the later style mounting pipe, that already used the later style o-ring. This is for the G/J ALH.

However, for the NB, they still show all three pipes (for both manual and automatic), with the pipe supersession showing the new number and o-ring.

The part number is on the pipe too. Odd that the NB's ALH water cooling page got no updates but the G/J one did.

gmenounos · Dec 1, 2019

For future reference, the original pipe is part number 038-121-065-A. If you have that pipe, you'll need the old style o-ring (WHT-006-407).

hopcarolina · Jul 20, 2021

Lots of good info there guys! Thank you.

I am wondering though, what holds that hard pipe I. The block. Is there some kind of retain clip or is there hold down bolt behind the accessories bracket?

Nero Morg · Jul 20, 2021

There's a bolt towards the transmission side of the engine.

Tdijarhead · Jul 20, 2021

If I recall there is a bracket behind/under the coolant flange and the other end is held by slipping into the block by the water pump.

AndyBees · Jul 20, 2021

This is the best photo I could find in my Albums. The pic is of the black hard pipe which I have cut for the purpose of modifying to fit my conversation project set-up. But, it is basically laying about how it would fit on the engine. It "wraps" around behind the head.

In the pic below, you can see the hard pipe protruding to the right along the same level as the end of the exhaust manifold

Below is another view. The hard pipe can be seen where it wraps around the corner of the block between to the two rubber pipes to/from the oil cooler. And, you can see where the return hose from the oil cooler Ts into the hard pipe.

KrashDH · Jul 21, 2021

I did a write up/how-to on here a while back, not sure how well the search function works...

AndyBees · Jul 21, 2021

KrashDH said:
I did a write up/how-to on here a while back, not sure how well the search function works...

Is this your "how-to" on the black pipe?

MKIV, Golf: Hard Coolant Pipe Leak

Hey all, So this weekend I tackled the notorious leaky connection at hard pipe and block behind the water pump. I can honestly say, just like the majority that have done this...it's a royal PITA! I followed this thread which really helped out a lot. Note that I didn't remove the pipe...

forums.tdiclub.com

KrashDH · Jul 22, 2021

AndyBees said:
Is this your "how-to" on the black pipe?

MKIV, Golf: Hard Coolant Pipe Leak

Hey all, So this weekend I tackled the notorious leaky connection at hard pipe and block behind the water pump. I can honestly say, just like the majority that have done this...it's a royal PITA! I followed this thread which really helped out a lot. Note that I didn't remove the pipe...

forums.tdiclub.com

Yeah I guess it wasn't as much of a how to rather photos of what I was doing at the end. I remember following the other thread to get it out. I don't remember any threads I was in posting photos so I decided to throw in a few

Coolant Hard Line Behind T-stat Housing, ?'s

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