1.6tdi overheating

[moon man]

So i was stuck on the m5, hours and hours, set off engine overheat light, taken to services fresh coolant, bled as good as possible
fast forward to now ...............'still overheating 2014 1.6 tdi diesel

intermittent loss of flow before the stat tries to kick in (heater goes cold)
The stat doesn't kick in , the coolant just rises in the reservoir
ideas ?

airlock I've run with cap off and squeezed hoses also used an extractor pump to draw water through the reservoir return pipe, no blockage
thermostat
reservoir cap, tried a known good one
water pump ,supposedly 2 yrs old but don't trust this info
doesn't really leak but maybe its not pressurising enough
head gasket , no bubbles can be seen with cap off
bag that is in some vag group reservoir's split causing blockage


anyway as i haven't done this for a living since the 80s anymore ideas, its booked in for a diagnosis but i have a coupe of days
if not i will post the outcome next week

tbf i may just get rid of this hateful lump of metal

 

[jpaul]

I never had bubbles when I had a head gasket blow/deteriorate and overheating - just excess pressure,
I think radiator cap 3series had an overpressure relief, which was blowing as I opened bonnet, and I left it half unscrewed and drove slowly home 20 miles or so

can you get one of those coolant exhaust gas test kits - I hadn't known about them at that time.

e: had had what I later realised was steam out of the exhaust a while before

 

[moon man]

I never had bubbles when I had a head gasket blow/deteriorate and overheating - just excess pressure,
I think radiator cap 3series had an overpressure relief, which was blowing as I opened bonnet, and I left it half unscrewed and drove slowly home 20 miles or so

can you get one of those coolant exhaust gas test kits - I hadn't known about them at that time.

e: had had what I later realised was steam out of the exhaust a while before

ah yes seen those, probably not time to get a test kit delivered ,i think the original overheating may have done some damage, think i would try one of the head gasket sealants if that is the case and do a retail trade in

 

[LuckyBenski]

Don't know if those sealant products are really recommended. Good eaybtomclog up and engine or coolant system