Bleeding Sigma

[Luegonigel]

Hi, I had a K series which was a devils own job to bleed the air out after radiator changes etc.

 

I now have a 150 Sigma which seems to have developed a mind of its own with regard to expansion tank level. I have fitted a bleed tee, jacked the car right up at the front (high enough?), checked the bleed tee, full to top and ok, took plug out of radiator, filled it, checked expansion tank somewhere sensible, put cap back on, lowered car, level at max, drove car, level now 20mm above max. when hot, same when cooled down. Conclusion, air still in there somewhere. Any ideas gratefully received.

[Jonathan Kay]

There are multiple threads on this. Here's a recent one.

 

What's the highest point in your circuit?

 

Jonathan

[RedCat7]

My Sigma had this problem after I upgraded from the standard plastic capped radiator to the all alloy one which I think is now standard on the 140. Trouble is the alloy version doesn't have the 5/16 bleed nipple which is T'd with the 5/16 bleed hose coming from the back of the head. I had the same symptoms until replaced the M10 bleed plug with a 5/16 banjo fitting plumbed the original T back in. Well actually I upgraded the plastic T to a brass one while I was at it.

 

Banjo Fitting

 

Tee

 

[DJ.]

If you don't have the set up mentioned by RedCat7, that is most likely the problem.

 

If you do, the system should be self bleeding, but I do find it difficult to get all 5 litres back in mine after working on it. The procedure I use is with the car level, I fill it by pouring into the top heater hose (valve open) until water comes out of the heater. Once I've attached the hose again, I top up the expansion tank. At this stage, I've usually got more than 4 litres in.

 

Then vigorous squeezing of both radiator hoses will bring the expansion tank level down. I continue until water is coming out of the pipe from the T mentioned above into the top of the tank.

 

At this point there is less than 0.5l to go in, and I run the engine for a while. While running the level drops, and without warming it up, I top up to level again. After the first drive, the level always needs topping up again.

 

Sorry if this doesn't help you, but as there weren't many answers I thought I'd pass on my experiences

 

Duncan

 

 

[Luegonigel]

That's the head hit on the nail thanks. The radiator was changed out about three months after I got the car from CC Midlands and one week before going to Picos mountains in Spain, they only had a plastic one in to replace the existing plastic one which leaked, fitted it the day before going......it leaked, went in Audi instead.

Alloy one fitted on return, that was June last year, I remember the tee piece becoming redundant but can't remember a bleeding problem. Engine and gearbox out last October to replace leaking gearbox seals, CC paid (good on them), can't remember a bleeding problem then either.

It only seems to have happened over the last few months.

I'll read up on the other threads but it sounds like there is the solution in there somewhere so thanks again.

[Luegonigel]

That is the deed done this morning so we will see how it goes. Expansion tank unbolted, lifted up 6" so now higher than radiator and heater bleed tee.

Engine run, no big gulps but level seemed to settle down, left when hot to let air escape for half an hour which it seemed to do.

 

To answer a previous question, the bleed tee on the heater is the highest point.

 

Tee and banjo fittings ordered to re-introduce the line from the radiator, previously removed when changing from plastic to alloy radiator.