Filling coolant, double tap sound from engine

[paule3d]

Anyone came across this before?

Trying to fill coolant and make sure no air in it. Put bottle above water reservoir. Water goes down, keep bottle filled so no air gets drawn in to the system, after a while the water level rises significantly and water comes back out of the bottle (around 1 litre), shortly afterwards the water level goes down suddenly (again, around 1 litre) and there's a loud "Tap,tap" sound from the engine block (most noticeable at 23 and 24 seconds on video)

Bit worrying!

Trying to diagnose overheating issues. New thermostat, sensors seems OK, fan comes on. Radiator is not blocked.
Car seems to lose coolant water, has for the 16 months we've owned it. Also has overheating issues in traffic etc, usually after some water has obviously disappeared somewhere. I've ordered a pressure tester for the cylinders.

Thought I got to bottom of it before as bled the system and gave it a good fill, wait for thermostat to open and shove more water in it. A few weeks later the damn reservoir is empty.

Any idea why the water level rises and drops so suddenly? And any idea what the plastic sounding "tap tap" might be?

Apparently I'm not allowed to post youtube videos, after typing all this....

[paule3d]

if anyone is good at internet etc, here is the youtube video id

XzO8wRcM-6E

e.g.,

.com/watch?v=XzO8wRcM-6E

[GrandadMonkey]

My guess is that you need a new water pump. The impeller can corrode away over time. This results in poor circulation and overheating.

An example is this thread:
http://www.peugeot206cc.co.uk/viewtopic ... 4&p=131739

You don't tell us much at all about the car. If the timing belt has been on for a number of years,when you do replace the water pump I would renew the timing belt, tensioner and follower pulleys at the same time.

[paule3d]

Thanks for reply. I've no idea about the car history with timing belt etc.

Do you know if changing water pump is a job an average home mechanic can do or does it require precision equipment and specialist knowledge due to timing belt?

[Capncol]

There is a "how to" on this forum

[paule3d]

Thanks!

[paule3d]

Thanks guys. Changed water pump and timing belt - the water pump had no impellers!
The loud tap - tap sound when the reservoir was emptying was filling every few moments (when engine was hot), has also gone.

Unfortunately the system is still losing coolant over a couple hundred miles, have to top it up every week.
Yesterday we did a 200 mile trip and I had to put 2 litres water in it again!

I can leave engine running for ages and not a drip of water to the ground.
The compression tests was even across all cylinders, around 130 - 140psi, so hopefully the head gasket is OK.
Does anyone have any idea where the coolant might be going?

One other thing in case relevant, the heaters never get very warm.
Also engine runs at 70 degree unless traffic jams - is this a bit low?
I've noticed the foot wells can be wet sometimes too, but more towards the rear of driver seat. Though once the passenger footwell had a mouldy patch - so maybe this is 2 separate leaks.

*edit* Done a bit more research since posting this and I can answer my own question - I think the heater matrix might be leaking. Will leave this here for search engines.

Thank you.

[IanL]

Compression is measured when the piston is high in the cylinder. A crack in the cylinder wall lower down could admit coolant. Any sign of coolant in the oil? (Not that a no is conclusive, as it could turn to steam and vanish with the blow-by gases via the crankcase breather).

[gazza82]

70 degrees is low (normally around 88-90 mark) ... it will be affecting your fuel consumption as it will think engine is cold so adding fuel .. you probably need a new thermostat too!

[paule3d]

The passenger footwell is soaking so I think the water is going there, coupled with heater never getting very warm, will replace the matrix in a couple days.

It had a new thermostat before as it was overheating (faulty water pump). I even checked the old one and both seem to work fine. Maybe it's just a faulty temperature sensor after all.

Thanks for the ideas.