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.