Bubbles in coolant , yikes.

[Dazco]

Went out in jambo at the weekend and whilst out had the dreaded red flashing light come on. Stopped ASAP ( thank god for Morrisons , stocked up with vitals at the same time. Anyhow , let things cool down a bit then had a gander, the level in the header tank ( the one with darlek sat on the top) was a tad low , the top up tank was just below the upper marker ( where it's been for a good while). I eased the darlek off slightly and there was a hiss of air and the header tank filled with coolant. I then squeezed a few of the bigger rubber hoses and had air pass into the header tank. ( now I'm getting worried ).
The temp needle has always sat just under the led and I did bleed the coolant system a couple of weeks back following the now famous brickworks method.
The header has a brickworks darlek, been in use about 8 months( I do have a brand new one also from b'works to try)
The oil was changed a few weeks back and looked fine and still looks ok on the dipstick. Not had any loss of coolant from under the van as far as I can see. She had pink coolant in at 50/50 and had that in when I got her. I believe Steve at gasure has serviced the van for some years so in sure the engine has been looked after.
Does this look like I'm getting a leak of exhaust gasses into the coolant? Next thing on my list is a sniff test. Any other possibilities that wouldn't be so catastrophic? And what do I check next. Thanks in advance . Daz ( very worried cos we are meant to be going to Cornwall in June and can't afford a new engine yet)

[Aidan]

ok when the light came on was the needle over 2/3 ?
did the led flash or come on and stay on ?
when you released the pressure the coolant boiled and blew through into the top up tank, that's fine, shows the cap holds pressure to 1 bar but will release excess pressure
the levels suggest the system needs a slight top up and bleed that's all unless the gauage is saying it is really hot
you can start the engine and remove the darlek cap and keep adding coolant till it's full you will see bubbles of air coming into the tank this is normal, when it's full then cap back on, reconnect hose to top up tank and check the radiator is full, monitor levels and top up if necessary till you are happy it's good, if it uses any coolant then check for leaks

[Dazco]

Light was flashing . When it was flashing the needle was way over to the right but swung over instantly. Prior to that its been bang on and on a run yesterday it was spot on. Ill put the new cap on just for piece of mind and top up and re bleed.
When I lifted the engine cover it didn't "smell" hot if you get my drift. Ill keep tabs on it over next week or so.

[mrhutch]

dodgy PCB connector at rear of dash gets my vote (along with coolant being a tad low). If the needle "swings" then it's electrial

[Dazco]

Compression test and bleeding this weekend

[Dazco]

ive done a compression test today and the results are as follows.
Ive never done a compression test before so all new to me, was done with a cold engine, but i did turn it over a bit first to get some oil round .

No 1:- 112 psi / 7.72 Bar
No 2:- 125 psi / 8.61 Bar
No 3:- 105 psi / 7.24 Bar
No 4:- 120 psi / 8.27 Bar

Ive read in the Haynes that the wear limit is 8 Bar so from the results i have 2 that are quite a bit under.
Ive re bled the system and topped it up.
Cannot see any leaks anywhere .
What do you good people suggest?

Daz

[Aidan]

compressions are ok it's only a 9:1 compression engine
No leaks and topped up I'd take it for a 40 mile round trip and see how it behaves

[Dazco]

its a relief to know that you reckon the compression tests are ok ish
just been for a 55 mile run through the peak district , ix of speeds etc and some steep 2nd gear climbs and one 1st gear down hill on winnats pass.
the needle never went above half way and when i got home the level in the darlek tank was the same as when topped up yesterday. all looking good for the Cornwall holiday.
Thanks for the advice Aidan, much appreciated.
Daz