Possible Bad Head Gasket

Hello all I'm new to the forum and need some help! I started my caddy last night and its got an MF TD from a mk2 jetta. I was purging the system and had the truck running for over an hour. It did not overheat but bubbles kept on coming up from the bottom of the reservoir. They were small but still there. No smoke of any kind, except a little puff of black since that was the first start since November, and the coolant that was cycling back was clean the whole time. The oil was fine too, just black lol. I'm pretty certain that it must be a bad head gasket, but I would really appreciate the input from all you experienced folks!
Thanks.

Yes, that does sound like a possible head gasket leak.... although could be air being purged.

A compression test with a quality gauge would be the standard next step, although if the void is small it can go undetected at cranking speeds.

People report mixed results with coolant testers.

Another common test is to let the engine get stone cold over night, crack the coolant cap to release any pressure, put the cap back on, run the engine at idle for 1-2 minutes, and then slowly open the cap again, listening for any hiss of pressure buildup.

If it is a dying head gasket it will likely reveal itself as an overpressurized coolant system after a spirited drive on the highway, where the extra pressures of highway driving lift the head a bit and make the void bigger.

Thanks for the quick reply, will try that out. My rad hoses could easily be squeezed when the truck started up and remained soft until the truck got hot. The temp guage was over the middle line tho and did not come down even with heater cranked up. The aux fan came on once when the temp got that high, but after that did not come on when temp got high again. I jump tested it after, and the fan is not at fault..would that indicate an air pocket?

Hmmm... our engines don't produce much extra heat and so the fan is rarely needed under normal circumstances... perhaps only on hot days stuck in traffic.

You'd need to see what the actual coolant temp was to be sure (the gauge is an approximation only) but in and of itself hard to say if what you've described is an actual problem with an air bubble.

On the other hand, your hoses staying soft is a good sign. Perhaps the best approach would be to just carry on and keep an eye in it... if it's a tiny leak it will take some time but will become more obvious.

Or... treat your aging car to a new headgasket and motor on for another 250K.

Ok makes sense, once agian I’ll take your advice and try purging again. If I can’t find anything else I’m hoping a head gasket will do the trick! Really want this thing running good again, lots of good memories made in the last couple years from driving it to high school every day
Thanks again for your advice!!