BKD coolant leak

[efeballi]

Hello all,
The dreaded coolant leak has returned.
Car had sprung a coolant leak many years ago, I put K-Seal in it and it was fine for years. Now it reared its ugly head again.

Period between coolant top-ups changes with driving style but is ~150 miles on average. I hear the whoosh of presssure releasing from the reservoir as I open the cap.

So far I've replaced:
Reservoir cap
EGR cooler
Hose going into transmission oil cooler

Exhaust gas sniffer on the coolant came negative. Coolant reservoir looks dirty but not abnormal for a 19 year old, 150k miles car. Car has a B revision cylinder head, but I can't see how the cylinder head can be a problem if K-seal can fix it.

I've recently read about watching for bubbles in the reservoir and checking for pressurization in the coolant pipes and will do them shortly. A recent pressure test done with the engine warm held 1.5 atm pressure no problem.

What would you guys suggest? I know it's a problem discussed to death but I'm at my wit's end to correlate internet findings to
what I have.
Thanks!

 

[Seatman]

Does the cooling system make a woosh noise when removing the cap with a cold engine?

After replacing the gasket I got no more woosh when taking the cap off on a cold engine. BRT lump, 2L single cam.

Try and get a pressure gauge on the cooling systam, see if the pressure goes up when giving it decent throttle going uphill. That was the real giveaway for me, you could watch the pressure rise as the boost kicked in.

 

[Rx7145]

This may not apply to you at all, but on the BRM’s there’s a head gasket coolant flange that likes to leak on the back of the head.

 

[efeballi]

Does the cooling system make a woosh noise when removing the cap with a cold engine?

After replacing the gasket I got no more woosh when taking the cap off on a cold engine. BRT lump, 2L single cam.

Try and get a pressure gauge on the cooling systam, see if the pressure goes up when giving it decent throttle going uphill. That was the real giveaway for me, you could watch the pressure rise as the boost kicked in.

Cap does whoosh when removed on a cold engine. Will verify in the morning.

 

[Seatman]

Cap does whoosh when removed on a cold engine. Will verify in the morning.

In that case definitely get hold of a pressure tester and take the car up a hill, you'll soon see if it's the gasket. Mine was leaking between a cylinder and the water jacket under boost.

You can see the sooty area

 

[efeballi]

Car left overnight, no whoosh when removing cap. Started car and ran for ~5 minutes, some bubbles came up but it could be due to me topping up the coolant before starting.
A makeshift idea is to put in a low quality reservoir cap to effectively reduce the pressure at which the cap opens, thereby not allowing coolant lines to be overpressurized and blowing coolant from overflow ports.

 

[Seatman]

Car left overnight, no whoosh when removing cap. Started car and ran for ~5 minutes, some bubbles came up but it could be due to me topping up the coolant before starting.
A makeshift idea is to put in a low quality reservoir cap to effectively reduce the pressure at which the cap opens, thereby not allowing coolant lines to be overpressurized and blowing coolant from overflow ports.

So not wooshing when properly cold? That's good. Mine always wooshed.

You want the pressure to help find the leak, check the radiator, bottom corners are a classic leak area.

Have ypu got an under tray fitted? If so it can hide leaks, be best to pop it off if fitted so you can get a good look underneath for wet spots.

 

[efeballi]

Slight bubbling in the reservoir continues with the car stationary and the engine being revved. When you get off the throttle at 4000 rpm a bunch of bubbles surface giving the coolant sort of a cappucino look, covered with bubbles.
Two short drives with low power and the engine barely warming up by the end of drives have caused ZERO coolant loss. Both were ~5 mile drives, though.

I'm aware of many 16V TDI's losing coolant due to gasket and cylinder head failures, with cylinder head part no.s ending with A and B being the most common ones to go (I have a B). How do I differentiate between the gasket and head being on the way out? Other thing that does my head in is how K-seal was able to sweep the problem under the carpet for YEARS.

 

[relumalutan]

This may not apply to you at all, but on the BRM’s there’s a head gasket coolant flange that likes to leak on the back of the head.

THIS.

Do you see any coolant on the ground?

 

[efeballi]

Can't see any coolant anywhere, I've heard that TL774F coolant glows with UV so I checked at night with a UV light. Nothing glaringly obvious anywhere in the engine bay.

 

[relumalutan]

Can't see any coolant anywhere, I've heard that TL774F coolant glows with UV so I checked at night with a UV light. Nothing glaringly obvious anywhere in the engine bay.

You are not going to find any coolant on the ground. I have a BRM and this is the story:
The coolnat flange is located on the driver side of the engine block. It has orange gasket which in time becoems britle and begins to leak.
It will leak only when the coolant reaches the operating temperature. At that point the thermostat will open, allowing the coolant to circulate. The engine block is defintely hot, the coolant dripping from the brittle gasket lands on it, evaporting very fast.

 

[efeballi]

Car passed a pressure test, ~5 minutes after I turned off the engine so the block was deffo hot and the thermostat was open. Will make sure to check the coolant flange.

Is the part code 03G 121 132?

 

[Rx7145]

03G 121 132

Yes

 

[Seatman]

K seal probably worked becasue the problem was small enough for it to do anything but maybe the problem has gotten worse.

Only way I know to test the head is for a machine shop to do a pressure test.

If it's gasket hopefully it'll be obvious like mine was. If I couldn't find

Car passed a pressure test, ~5 minutes after I turned off the engine so the block was deffo hot and the thermostat was open. Will make sure to check the coolant flange.

Is the part code 03G 121 132?

Tested while driving? Mine only showed up when boost kicked in and engine was under load. You could just watch the coolant pressure go up and up going up a hill.

 

[efeballi]

K seal probably worked becasue the problem was small enough for it to do anything but maybe the problem has gotten worse.

Only way I know to test the head is for a machine shop to do a pressure test.

If it's gasket hopefully it'll be obvious like mine was. If I couldn't find



Tested while driving? Mine only showed up when boost kicked in and engine was under load. You could just watch the coolant pressure go up and up going up a hill.

Tested in the shop, no driving. I'll have to brew up my own tool to pressure test.

 

[Seatman]

Tested in the shop, no driving. I'll have to brew up my own tool to pressure test.

Yeh I had to borrow a tester then strap it to a window wiper, sitting still was fine, pressure only went up under load and that's what finally gave it away that it was the gasket. Obviously when the turbo kicked in and raised the compression it then forced air out the cylinder and into the water jacket.

 

[Seatman]

Ps when I posted about my coolant issue some suggested it could be the egr cooler, I diconnected and bypassed it to check.

 

[efeballi]

Brewed up a pressure tester from a 3D printed coolant cap, a tubeless valve, some tubing and an electric tire pump. Passenger observed no change in pressure or no air coming through the tube throughout warmup or in any of the pulls I did.
EXCEPT when we turned off the car, a little burst of air smaller than what you'd blow to blow out candles came through the pipe for a few seconds.
Car also loses coolant when cooling down.

 

[efeballi]

I've found a tear on a pipe under the EGR/ASV valves. The pipe's integrity is not broken, but the surrounding area is all black (maybe oil/PCV? No oil leaks though) and does not glow with UV.
I will upload pics in the morning, Imgur appears to be down.

 

[Seatman]

I've found a tear on a pipe under the EGR/ASV valves. The pipe's integrity is not broken, but the surrounding area is all black (maybe oil/PCV? No oil leaks though) and does not glow with UV.
I will upload pics in the morning, Imgur appears to be down.

Soot from the egr or that?

 

[efeballi]

Best pics I could get at night:

 

[efeballi]

Coolant flange's been replaced. Not enough mileage yet to know if it solved the problem, fingers crossed.

 

[efeballi]

Flange didn't solve it. No change in nature of leak.
I 3D printed a better coolant reservoir cap and fitted a bike valve on it. I can't say it's perfectly airtight but it's pretty close.
We routed a hose from the reservoir cap to the passenger window (rolled a little bit down) and hooked up an old blood pressure meter to the other end of it. Co-driver monitored pressure gauge as I drove.

Observations are:

-no crazy pressure spikes when WOT --> no combustion leakage to coolant circuit. I'm now 99.95% sure it's *not* the gasket and 90% sure its *not* the cylinder head. Full beans were given for >10 seconds, uphill.

-coolant circuit develops slight vacuum when engine is revved on neutral, goes back to zero when engine returns to idle RPM

-slight vacuum when engine is stopped

My current bet is that the engine has a leak on the external coolant circuit (radiator etc.) and the course of action is to remove the front bumper to have a goooooooood look at the radiator and connections.

 

[efeballi]

Made an even better version of the custom reservoir cap to check the nature of the leak, or rather, nature of the pressure buildup during the drive. Pressure rose up to 300 mmHg which was close to the limit of the pressure monitoring device I used (a blood pressure gauge). 300 mmHg is in line with the vapor pressure of 50/50 water/coolant mix at 90C.
There's another coolant flange at the side of the block, facing the front of the engine (edit: it's the thermostat housing). Being under the EGR and ASV valves, it is drenched in oil from PCV. The seals of the coolant flange and things attached to it are probably fxxked if they were in contact with oil for so long.
Problem is, I can't find the part no. for that coolant flange.
Oh, this coolant flange is the one attached to the split pipe I posted above.

 

[efeballi]

Bought/ordered all parts to clean and replace all seals from boost pipe to intake manifold. Removing these will give me (or the mechanic) easy access to the thermostat housing. Will replace thermostat, housing, temperature sensor and the torn hose a few posts above.

I've got the part numbers but I can't find the o-rings that mate the two ends of the EGR valve so decided to get FKM (aka Viton) o-rings of the correct size. I found them listed as 62x3 between EGR and manifold and 55x2.5 between ASV and EGR.