Hi. I have a VRS 170 PD. Been having slight coolant loss issue for some time, vag specialist said couldn't see any obvious leak but no signs of obvious head gasket failure. Needed new thermostat and an oil change and he flushed the coolant as car was also struggling to get to temp. Car ran better, still slight coolant loss. A little while later after a long but painfully slow run up to Liverpool from Brighton my DPF light came on along with glow plug flash and engine light and car goes into limp mode. Great. RAC man came out, diagnose and starts dpf regen and even toon it for a drive then returned ot back to me all clear (was 52% full) and car good to go. I mention coolant loss, rac man says probs little heater matrix leak and coolant is evaporating. I have a cup of tea. Before I leave the services where I called the rac from I decide to top coolant slightly. Engine is still warm so carefully undo cap with hand protection. Weird thing happens.....i get a hiss and some off colour water comes flooding back into the expansion tank. Never happened before. On the rac mans suggestion when I get to Liverpool I throw in a half bottle of rad weld and walla. 1500 miles coolant is steady as a rock. My question is was it the rad weld or was it something to do with the dpf clearing that solved the coolant issue? Another question, is there a scenario where my car would just be unable to regen itself (dpf) cos from my understanding, 52% is a lot and I'm telling you, I drive this car as it was intended to be driven, hard and I regularly follow the dpf regen protocol of 4/5 gear and 1800-2500 rpm for 30 mins. Please discuss.......

I can't imagine how a dpf regen could affect coolant loss so the gunky rad weld will have solved your coolant leak. I don't like the stuff and such approaches are usually thought of as a temporary solution but I know some people have had long term success.

 

Always makes me a little concerned about what it could do to flow in engine coolant lines and contained block and head capillaries.

 

DPF life and regen is not my area of expertise, but if 52% is after 9 years driving that's not too bad is it?

I figured its cheaper than a new heater matrix and tbh was more like 1/4 of a bottle. The smell of coolant slightly from the hot air has gone now too so i reckon it's solved it and rac man was right. I'll get another oil and coolant change in a few months as I like to keep on top of these things. 52% from 9 years I suppose your right, isn't much just worried it was so full cos my car isn't performing regen properly....we'll see, I'll check it again with computer when it goes in for next fluid changes.