Was checking my D2 earlier today for coolant leaks ( and yes the hoses are old and leaking in several places and the coolant tank seems to have a crack, I will replace all of them).. but also observed coolant bubbling. Especially after idling for about 10-15min and bubbling increases as I rev up to 2k rpm. At first crank there is white smoke but kind of goes away after a bit. engine oil cap has a bit of condensation inside.

Please see attached video and a pic of under the oil cap. Thank you in advance.

 

Video of coolant bubling

 

Well that is not a good colour but how far and how long do you drive on average. If you are constantly doing short trips, sub 20 minutes you will get build up on the cap.

As to the video is that actual air bubbling or coolant moving, you will always have coolant motion at that location, it is the return from the intake manifold.

My suggestion is clean your oil filler cap up really well and drive as normal for 2 or 3 days and see if it re-occurs

 

The chemical test kits are not always accurate on a small leak, so that might not help. You can borrow a pressure test kit from Advance and see if the system will hold pressure, but the test could damage the hg further. If it is not bad you can drive it with blown hg for weeks if you run the cap one full turn loose, but you will eventually need to change it. About 18hrs round trip of work to change them them and a good long term update given the age.

 

Thank you very much for the replies. I just bought this car and been waiting on parts etc to do the ‘known’ fixes aka inline thermo, coolant hose replcement, drive shaft etc. i just hooked up the ultragauge and for a short 10min ride it shot up to about 220F ( no inline mod yet, and some coolant leaks, really old oem thermostat). I havent yet driven too often but the previous owner was an older man and he used it for short trips and taking his dog to the park etc.

Really good suggestions on cleaning the cap and observing for a while. Will do that for sure.

 

As for the video I dont see air bubbles and even that circulation aka bubbling I saw was after engine was idling for 10min and temp around 170 or more. Will retest tomorrow in the day to check on exact temp when it starts that bubbling.

 

Ahh, what a relief for me to know this. Thanks.
I've been wondering about this on Betty...