the_kid_hartford

I have a 2009 D3 with only 38k miles but it has a slow coolant leak that started about 6 months ago. I know there is a ton of info on this forum but a very, very good mechanic in central NJ cannot find the source.
It has been pressure tested 4 times......now even a week of dye thru the system has not turned up any leaks.....could my D3 bought with just 27k miles last July really have a major problem, like crack in head????? If the dye turns up nothing and there is no coolant in oil and no visible leaks....where am I at????????
Any thoughts from the experts would really be appreciated, it is not looking good.

Jack88

About how much do you have to add how often? Any odd smells, or white sweet oily smoke from the exhaust? There are places it can leak around the back of the engine where it would burn off on the exhaust, so I'd point to look there for any signs of leaks first.

the_kid_hartford

I made a mistake in my post, not 6 months, but rather 3 months.....in Dec it was slower than it is now. I added once in Dec--2 times in Jan and now in Feb. about 4 cups last time.
Another problem is coolant low sensor is not coming on anymore. when this first started the sensor came on as soon as it went below minimum. Now it is well below min and never got warning.......
I will ask mechanic if they checked behind engine....anything specific?

Thanks for your help

JohnnyJ A6Q

Hello Kid,

Tell us which engine you have to narrow it down some, A8-A8L-4.2, S8-5.2, A8L W12-6.0.

I can tell you that when I first received my W12 6.0 it had leaks in the plastic tubing at the rear of the engine, and my low coolant warning stopped working also, I just replaced the whole tank and cap after fixing all leaking lines and hose.

look to find a pinkish crust around the leaking area, and as already stated it can hit the exhaust and burn off, therefore never reaching the ground.


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the_kid_hartford

thanks, I have the 4.2.....I am assuming that the dye will leave some residue somewhere.....

JohnnyJ A6Q

It should, but you will need the UV light and glasses to see it, and I would be checking that personally if I were you, and or the pink crust from the coolant should start to show itself soon.

Be sure to check around and under the coolant tank, radiator, etc, I have seen it steam out of the radiator core leaving nothing on the ground and only leak when in operation.

Do you smell any sweetness under the hood when you first open it hot ?


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Shark_V8

I would highly doubt cracked head. Perhaps a nicked o-ring though. I have not traced through the system yet so can't offer advice on suspected spots tho.

Curious as to when the leak down test was done? Ideally I'm thinking dead cold and have it sit for a few hours at test pressure. What is the leakdown spec?

PS: On my service record, there is noting of crusted coolant/ suspected leak. Pressure tests and no fault found (@ dealers and indie shops).

And then our keen noses whiffing coolant every now and then. I just used some Prestone stop leak 1/2 bottle not a problem, not losing any coolant, never have really. Smell is gone too.

MP4.2+6.0

Check everything noted here, plus the heater valve block under the plenum cover; maybe water pump if older/higher miles (see below).

As Johnny noted, you look for that pink fluffy residue when coolant burns off if no drips are obvious. On my D3 W12 over the 9+ years, I've had an o ring leak at the upper hose, another o ring at the small secondary hose toward radiator bottom, the radiator itself (tiny and never dripped; found a damp look in lower corner pre-warranty expire and got a new one); leak at loose heater valve block clamps (early on; warranty), cracked hoses with heat soak over the years at rear of motor like Johnny noted and that dealer maintenance seemed to exacerbate (later found their non factory splice and clamp kludge; thank you Rector). Also had a drip at one heater bleed valve due to a worn o ring on the sealing screw.

Also possible it is leaking at water pump bearing, and on a 4.2 5V you need to pull timing belt covers to see that if it isn't obvious from dripping. Not very common though, and water pumps that bad off are often also making bearing noise.

the_kid_hartford

Thanks MP4 and Shark.....I really appreciate the info....Shop wants me to drive for two weeks and let dye really works it way around before checking for 2nd time with light......will give updates when and if found.

richard-tx

Dealing with small leaks is a problem. I have had to make a special pressurization setup involving a regulator because of a small leak that I could not find. After the cooling system was pressurized for 24 hours, I could find the leak. Once I found it, I took the hose off, cleaned everything and reassembled. No more leak.