Coolant Loss Etc

[francois]

Hiya,

Any general advice on the following:

My W reg Avenis 2.0 SR 150k on a 3SFE, overheated the other day (doing about 70mph), the engine light came on then 2 minutes later steam started coming from under the bonnet and temp gauge went up (shamefully i hadnt checked my levels in over a month). I pulled over immediately and lifted the lid (coolant was boiling in expansion tank), I took off rad cap and let it all cool down, filled up with water (took about 5 litres) then drove it home. I let it all dry out then topped up with water so rad was full and expansion tank to max line and took it for a spin. No sign of overheating, and no signs of leaking. So, took it for a proper spin on main road, no overheating at all. However seemed to lose a lot of water/coolant (best part of a pint in about 30 miles), but no signs of leakage anywhere. Also there was bubbling in the expansion tank, which didnt smell of exhaust and no oil film and which slowed down with time, so I am assuming this is air that got in during the overheating episode. There was no hissing from expansion tank. No gunge on oil cap or dipstick either, and no water coming from exhaust.

I know there is small leak in rad core, but this isnt enough to even drip, it just leaves a little dry deposit, its been like that for yonks. basically, i cant find any major leak with engine on or off, or hot or cold. And I cant get it to overheat either which implies to me the head gasket is okay.

I'm thinking in order of severity: radiator cap (seems ok), radiator leakage is more than I think, thermostat is playing up, water pump is about to fail or head gasket is on the go.

the question is did it overheat because the water ran low, or ir is it something more sinister?

and where is that damn coolant going?

I'd like to know if there are easy tests i can do to narrow it down a bit before I go to a garage, . I also think I need to bleed the system of any air, not sure how.

[francois]

bump

[igormus]

checkc with gasket packing on the expansion tank lid

the less pressure the less boiling point (100 C) -- it might you have this effect fo de-pressurisation of the system.

besides -- are cooling fans in order? control sensor el contacts ? thermostat?

regards / Igor

[francois]

hi thanks Igor,

you mean seal the expansion tank lid so nothing escapes, and see if it starts boiling?

cooling fans work ok

dont know about control sensor

not sure about thermostat, I only checked top and bottom pipes after going for a run in it, so they were both hot, which i guess is normal. Should I check them as the engine warms up too?

when car starts there is a water gurgling noise behind dashboard for a few seconds

cheers

[igormus]

hello again

- as to exp tankk lid ---- the cooling system must be under pressure assuring you the coolant will be be boiled !!! - it is not a kitchen kettle . it is understood en expension pressure will be relieved thru safety valve/plastic tube right on the tank top.

- as to fan control sensor --- in static condition you can have this sensor screwed off and just using normal water boiling in the glass + thermometer + multitester -- check at wat water temperature the sensor passes signal. AFter that you should check with repair manual what temp fan is ON at. The idea is simple to understand whether sensor works or not;

- as to thermostatic valve -- it is understood you should check it when engine is at stable working temp , let say after small drive. touch all IN/OUT hoses temperature.

- as to water gurgling noise --- most probably you have an issue with either steam blockade or an air is still in the system and you have to bleed cooling system.

regards / Igor

[francois]

Hi Igor,

Thanks for that advice, I tried the hoses, it wasnt right, as if radiator not working so I got a mechanic to look at it (they didnt charge me, which was good). He confirmed the radiator is blown (seized up?), however he thought there may be head gasket trouble developing, but he couldnt be sure.

i'm booked in tomorrow to get the radiator changed and the head gasket inspected, in a garage that does head gaskets.

how much should I expect to pay for head gasket to be fixed, if there is a problem?

cheers

[igormus]

the head gasket issue is the worst cos you will have to strip the engine and purchase more consumables -- i have no idea

the diesel avensis owners might help, sorry matey

regards / Igor