Hi - I'm currently baffled by this one.  Coolant being lost at an alarming rate but no signs of leakage.   Have had to top up approx 4 litres in last 500 miles and car was apparently fine before.

 

Expansion tank filled to max at the weekend and I had to put in another 2 litres on commute to work this morning.  Absolutely no sign of leaks anywhere.

 

Head gasket?  possibly but motor starts and runs fine without signs of steam/water from exhaust.  Does use quite a bit of oil though as well.  Car has 185k miles on it.

 

Anything specific I should look for?  

Radiator remaining stone cold but radiator in/outlet pipes are very hot. Had thought maybe stuck thermostat but now suspecting water pump having read a few threads on here.

 

Temperature through the roof on way home tonight.   Still baffled by the coolant loss though.

 

 

Water pump is a possible shout. You won't see a wet patch under the car as it may only be leaking through the seal to the external belt drive sprocket when it is spinning and subsequent leaking coolant is evaporating off on the hot engine.

Otherwise have you checked condition of the oil, Any mayo coloured gunk on the underside of the oil filter cap indicating possible head gasket issues?

That does suggest either a disintegrated water pump impeller (get the cambelt done at the same time since the belt has to come off to change the pump) or a sludged radiator.

 

So, as an investigative question, what colour is the coolant?

That does suggest either a disintegrated water pump impeller (get the cambelt done at the same time since the belt has to come off to change the pump) or a sludged radiator.

 

So, as an investigative question, what colour is the coolant?

 

Coolant is dark grey instead of blue, but no signs of oil.   Also no sludge under oil cooler cap.

Coolant is dark grey instead of blue, but no signs of oil.   Also no sludge under oil cooler cap.

Yes, but G12(++) should be pink or orange. If you've been using glycol (blue) rather than OAT, then I think you may well have a sludged up radiator (if you're lucky; if you're not then the block is sludged up too).

a couple of photos......

 

coolant tank this morning, so its lost a little fluid overnight, maybe 250ml or so.

 

 

ran engine at idle for a couple of minutes and got about half a pint of coolant through from the return pipe which I disconnected and fed into glass......increasing idle speed made more coolant flow, but not necessarily the same at sustained fast driving speed.  I guess water pump working to some degree then, but not sure how effectively.

 

After a few minutes at idle, top radiator hose was warm, lower one was still cold.

 

:coffee:

Edited 8 September, 20169 yr by Fastblack

That coolant is nasty and cloudy, and it's also glycol based in a car that should be using OAT!

Looks like an alco pop.  As mentioned it should be using G12 long life!

So - wrong coolant then - but that's not what's causing the problem.  It's been there for over a year without problems.

 

G12/OAT will go in when the system is repaired.  Still showing signs of a stuck thermostat but intemittant.   as radiator sometimes hot, sometimes cold.  Same with heater.

The heater should still work whether the thermostat is open or closed so its probably the water pump impellor loose on the shaft.

It may have been over a yr but its orobably just taken that long to start causing a noticable issue..

id be dumping it out and flushing to refill with g12.. and changing the water pump & belt (might as well while in there..)

The black section at centre of photo I guess the coolant pipe unit on left side of engine.  Has connection for car heater and off to upper radiator coolant hose.  Massive airlock as this is regularly devoid of coolant as far as I can see.  Disconnected upper rad hose today to check and hey presto, nothing there but air.

 

 

Have got new water pump and thermostat to go in - less than £30 for both 

 

Will get trusty local garage to install along with new cambelt which I suspect is due now.  Car has sticker in sunshade saying last change was at 125k, now at 185k, but i've no idea if the 125k note is genuine.  Anyway, new one going in with pump.

 

According to receipts, radiator was new around three years ago so I think its probably ok but going to flush and see wot appens.......

Edited 10 September, 20169 yr by Fastblack

Current status:

 

1.  Drained cooling system at radiator stopcock until no further drips of fluid.

2.  Removed thermostat to replace it and a further 1 litre approx flew out of thermostat port.

3.  Renewed thermostat and flushed radiator - no signs of anything odd.

4.  Refilled system at expansion tank.

5.  Drove approx 15miles and parked up.  All ok.  coolant at 90 degrees and heater and radiator warm.

6.  After being parked approx 1 hour, drove back and coolant boiled within approx 3 miles.  Upper and lower radiator hoses under high pressure, difficult to compress.  Radiator cold.  Heater blowing cold.  

 

Did you bleed the coolant system? Or did you just pour it in then take it a batter down the road?

To the best of my knowledge I bled it - fed coolant in slowly and left it to settle, then squeezed upper and lower rad hoses to try to expel air.   Let it idle for a few minutes then switched off and checked level.  Then left it, engine off, for 20 minutes or so before rechecking and setting off.    As I say, for the first 15 miles or so everything seemed fine, then after I'd stopped and restarted the coolant boiled, no hot heater air and cold radiator...........

 

Is there a better way of bleeding the system - can't find much in Haynes? 

We usually pour coolant in it, start it up and idle for a while, the sit with the revs at 2000 or so with the cap still off the expansion tank. Have the heater on warm and you'll feel hot air coming through eventually, if its staying cold then you've still got air somewhere and will need to put the cap back on and rev it with the cap on until hot air comes through. If you've already taken it a drive then really it shouldn't take long.

 

Just sounds like the whole system is pressurised (you can't squeeze the hoses) and either airlocked or not circulating properly (no hot air).

 

So its either air in the system, or its your water pump. 

 

If its identical to before you drained the system, then its more likely to be the water pump.

I had this on the wife's 1.9tdi A3 on an 03 plate. Started overheating/loosing coolant, AA diagnosed the thermostat. Changed that and problem persisted. Turned out to be a tiny knick in the head gasket.

I had this on the wife's 1.9tdi A3 on an 03 plate. Started overheating/loosing coolant, AA diagnosed the thermostat. Changed that and problem persisted. Turned out to be a tiny knick in the head gasket.

sounds like a blockage somewhere...... happy hunting :(

Like i said before, the thermostat sticking shut would not affect the heater, you need to change the water pump.

Garage (a good un in my experience) says head gasket goosed