M20 Coolant Bleeding - I have checked the Wiki!

[MattCyclone]

Hi all,

Car's been working well, though drinking a bit too much fuel and taking a while to warm up so I thought I would treat her to a new thermostat when I did the summer service.

New Oil and filters in, so onto the thermostat and coolant change - did what I did last time (no thermostat change though), took the rad off and blasted it through in both directions with the hose - re-assembled and slowly filled the system again, took the top heater stub tube off, liquid flowed both ways so checked everything and fired her up...

Warmed up quicker as it seems there is an air lock!! So, please let me know if there is anything I have missed:-

1. Up on axle stands at the front anyway.
2. Thermostat change and rad blast through
3. Filled system slowly.
4. I didn't drain the block (as the coolant is only a year and a half old).
5. Checked flow from both top heater pipe and stub sticking out of the bulkhead - also checked only fluid came out of the bleed valve.
6. Even did the blow through the overflow pipe to ensure it was good (when I checked the second time)
7. Engine temp reached 1/3 an no heat from the heaters...

Any advice greatfully sought!!

[Speedtouch]

I presume you have undone the bleed valve by the thermostat to let the air out? Try squeezing the hoses to help remove the air, and rev the engine a little as you bleed it.

Sometimes, letting the engine cool down again, then top up the coolant as necessary, then bleeding again will work. You may need to repeat several times as required.

[MattCyclone]

Speedtouch,

Thanks - I had opened the bleed valve and it seemed to stream a constant supply of coolant... I will amend the list of 'already done' above...

I will try it again this evening, just a bit frustrating as I have managed to bleed it twice before with no issues by following the instructions I put above.

[Rtaylor2208]

The way I have done it a few times and its worked every time:

1. With the coolant topped up, start the car with the heaters to full heat and on number 4.
2. Let it heat up till just below the half mark on the guage.
3. Open the bleed valve, let coolant run out until the bubbles stop and the heaters are warm.

Keep an eye on the temp guage during this time.

[MJJ_ZX6RR]

You did not put the stat in the wrong way round did you?

Just wondering, as a *ahem* friend did that recently and the coolant system would not bleed for love nor money.

Martin.

[MattCyclone]

Hope not! Got me wondering now...

I had it so that the spring is inwards, towards the cylinder head.. Also, why would that stop the system bleeding?

I may very well drain enough off again to check it - then I can fill it from scratch and hopefully cure the airlock...

Cheers...

[MJJ_ZX6RR]

I would imagine it is more to do with the rubber o-ring then being on the wrong side rather than the stat back to front.

Find your car on http://www.realoem.com, look at the engine cooling section and there is a nice exploded diagram of which way round stat and o-ring need to go. Just in case you got it mixed up, like me.

Martin.

[MattCyclone]

No joy bleeding again, as the top stub heater hose is not getting warm then I assume there is an airlock in the heater? Even though I have done the hose off, cover the top of the expansion tank and plugged the loose end of hose and blown at least 2 litres through the heater??

Will empty the system tomorrow and start again I think... Filling it even slower! I will also run a hose right through the system until I see clear water running through the heater.

Any other tips??

[MattCyclone]

All done, though now the temp sits at 3/4's, rather than the half it did before...

What do people think, rad partially blocked from me pushing a load of water from the hose through it or does the water pump sound like its failing... Any way of checking either?

[Speedtouch]

As long as it's not going anywhere near the red zone you'll probably be OK. Have you tried checking the brown temperature sender with a multimeter, or swapping it for a known good/new one?

I doubt you will have done any harm to the rad, but you never know if it's an old one.

A worn water pump will normally either screech or have a rumbly bearing sound - try waggling the fan from side to side to check for play.

[MattCyclone]

Thanks for the quick reply...

I think the brown sender is fine, as it was before the thermostat change and I did not disturb it. I will try and check it though I imagine the difference between half up the gauage and 3/4 of the way up will be very little?

I will check the fan, the engine is pretty good noise wise apart from the ticking injectors and (I think) a small crack in the exhaust manifold which ticks...

[clipper]

Partially blocked rad would really only show up when you're working the engine relatively hard, up hill motorways for example.

Sure you got the right thermostat ?

[MattCyclone]

Hmm, bought one of ECP using my number plate.... Any way of checking? I still have the box...

[MattCyclone]

Clipper - you are good!

Upon checking the box, you are correct, I currently have a Volkswagen thermostat in there! ECP will replace it (luckily without me having to remove the one from the car) so I will change the thermostat and go from there...

Annoying but at least I know the cause (hopefully!)

[Speedtouch]

This goes to show, that it's best not to rely on just giving your numberplate when ordering parts - you know what these monkeys are like behind service counters!