Troublesome coolant loss
 

Some know I replaced a headgasket in an 03’ 3.0 a few years back and have had no problems with it for about 15k miles. Recently my low coolant warning triggers every 50-60 miles or so and I have to add enough coolant to make it right.

I just pressure tested the cooling system and it held pressure (25 lbs) for 30 mins. And 30 lbs.

As suggested I pulled the spark plugs and tested for coolant in the cylinders but found none- I swabbed the cylinders with a soft piece of rope that would have absorbed anything on top.

Other symptoms: seems that the upper and lower radiator hoses hold pressure longer than I remember on cool down (maybe my imagination).

Yesterday on cold start I noticed a puff of white/maybe grey smoke from the tailpipe. Didn’t persist.

Interior temp gauge straight up 12 noon but seems to get there quicker than it used to - summer maybe?

Replaced spark plugs, previous had signs of being cooked so maybe wrong type? New plugs running great.

Would a pressure test reveal a head gasket issue? I suppose my next step is a block test.


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Are you seeing leakage under the car???
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Was there one or 2 of the spark plugs that looked different/cleaner than the rest?

Don’t guess. Put in dye and use a black light to see where it’s really leaking from. The most common cause is the plastic overflow tank.

As noted, UV Dye is a good test...I often use it to find hard-to-find leaks. It will also show up in your tailpipe if you have it in your cylinders.

You may have to buy the UV dye (for cooling systems) separate from the UV flashlight and glasses, but you can buy both on Amazon for little $$. Pour only 1/2 the little bottle (not a full bottle) of dye into your coolant and run it for a bit..at least up to op temps..

I am concerned with puff of white smoke out tailpipe on start-up..I think you may have coolant in cylinders despite not finding any.

A coolant pressure test will usually not reveal a head gasket.

Do you have exhaust gasses in your coolant?

There's a chemical test to rule out exhaust gas in the coolant. Head gasket leak will go both ways and much more pressure in the cylinder than in the coolant.

Most missing coolant without a drip are from a slow leak that evaporates.

In my case those have been the radiator outlet sensor and the reservoir seam. I've fixed both of those on both of our e53.

I don't know if the M57 has a weep hole like on a N62, but if so that's where I'd check.

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Troublesome coolant loss
 

Thanks. Good tips all

No drips on the ground but AC condensation.

I have the glasses (somewhere) so I’ll try the dye or do a block test.

When I pulled the spark plugs all were the same but #6 had a little bit of oil on the threads.

I’m going to change oil and filter soon so maybe that will tell? No mayonnaise under the oil filler cap either.

I’ll check Waterpump for weeping, and the overflow tank (this one was replaced last year from a failed one.)


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For some time when I first got my 05 X3 soon after ownership [emoji360]there were damp spots[emoji98] of what turned out to be coolant under the car. I put up with it for a while. Well, when the adding of coolant became too frequent and the low coolant light appeared l began investigating[emoji1992]. The tank was not damaged none. Turns out I read an article (I was new to bmw) that indicated that sometimes the problem was a simple worn -O- ring... sure enough that was the case for me then[emoji313].

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Which o-ring? I bought a ten pack of the model for the lower radiator sensor and needed almost half of them between the few cars I helped maintain