Coolant System Bleeding

[Jeff Ovens]

I recently suffered the famous popping off of the front rad hose (after buying the car two weeks ago!) loosing a couple of litres of coolant. It happened after a good motorway run, then getting stuck in traffic. I felt a thud through the chassis (the hose coming off) then temp rose to around 103 deg (started flashing) then I shut down. I refitted the hose (difficult job due to lack of space but straigtforward) re-filled and bled the system. My coolant temp is now slightly erratic. If I'm pootling around at low engine/car speeds the temp can rise to around 91, however I notice that if I dip the clutch and rev the engine a few times, the coolant temp suddenly drops by up to 10 degs, tehn returns to 'normal'. I suspect that there maybe air in the system somewhere which is causing this behavior. This is the question - does anybody have a tried and tested coolant bleeding method that they can divluge? - I've scoured the web to no avail! My method was to fill the system then run the engine (from cold) with the front bleed screw open. Strangley even when the engine is fully warm, water does not conitually pee from the bleed screw, however a rev or two starts the flow. I need to get this sorted as I know how delicate the head gasket is on these units. Having just bought the car my knowledge of such elise detail is lacking so will welcome any methods or tips to do the job properly. (PS - No regrets on buying such a great car however!) Cheers

[fergusd]

You know about the bleeding vents in the system ?

There's one on the left hand rad pipe, close to where it connects to the rad, and there's on on the left hand side of the engine, on a steel coolant pipe, you should check these to see if any air comes out.

There is a bleeding procedure that Lotus specify which includes a pressure bleeder, however most people manage by removing any air using these vents.

hth

Fd

[Jeff Ovens]

Cheers fd.
I have heard several reports from people experincing head gasket failures in the weeks following the release of the hose. It doesnt instill much confidence in the car now and is spoiling the whole driving experince due to one eye on the road and one eye on the Stack temp reading!! Can anybody put my mind to rest?


I am aware of the bleeds and have bled the sytem several times now. I still get this erratic temp drop when I give the engine some revs. I'm not sure if this is normal as I never looked at the temp before the hose came off as much as I do now. Do others notice this on cars that havent suffered this hose release problem?

I'm tempted to take the car to my local lotus dealer and allow them to carry out the bleed to the Lotus manual.

[fergusd]

It does sound to me like you have an airlock, better safe than sorry, I'd make sure it was bled properly too :-( . . . HGF is a weaknedd of the K engine, and some cooling systems, especially earlier cars, can be difficult to bleed. The later cars had a design change to the cooling pipe routing in the engine bay which makes bleeding easier . . .

Fd

[Stevef]

I hate to be pessamistic, but those fluctuating temps could be a symptom of a HGF. I wouldn't drive the car until you get it checked out. I melted a VHPD head following a HGF, which was expensive.