So I thought the head gasket had failed on my 2.0 petrol. It keeps pushing the coolant out the bottle with lots of pressure at the cap when warm.

Short story:

How do I checked if a water pump has failed or help narrow it down?

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Long story:

I Started looking into it tonight and started with the sniff test!

Zero engine gasses were found in the coolant which is good, tested it twice at different revs until it boiled over (not enough to do damage tho) and it was clear both times.

Next check was a compression test to see if the head was warped or anything similar. All four cylinders were the same with about 180psi, good!

Next check was the thermostat. I removed it completely to see if the coolant still boiled over. I checked the thermostat with the boiling water test which if failed, but didn't cure my problem.

Last check was the matrix for any blocks, came through clear.

So with everything pretty much tested... My last resort is thinking the water pump might have failed (it is due anyway with the belt) but how do I test or check a failed water pump?

If the timing belt's due anyway, replace it and inspect it on the bench. That'll give you a clear picture as to whether it's the water pump or not. Check it for cracks etc, check the movement of the impeller and if any blades are missing if possible. If it's not the water pump, further inspection.

Which 2.0 petrol engine do you have please?

The waterpump failed in my 51 reg 2.0 8v Bora. 

Same engine I think... 

Typically, it happened en route to my sisters wedding. 

Plastic impellor came away from the spline and stopped 

turning although the spline was spinning like a good un apparently. 

Had the cam belt(Thought I may as well)  and waterpump done and 

all fixed. 

Pattern part metal impellored one went in after the breakdown. 

 

Edit, seems it was an 8v

It's an aqy engine I believe.

I'm still thinking of getting rid, don't even know if I should spend £60 on a water pump and timing belt kit...

I would like to know if I can diagnose it any other way.

Is it the venerable 2.0 8-valver found in Golf IV etc. or a later 2.0 multivalve?

It is a 2.0 8v from a mk4 golf, beetle etc....

Don't know much about them I'm ashamed to say.

It is a 2.0 8v from a mk4 golf, beetle etc....

Don't know much about them I'm ashamed to say.

 

Scant consolation I know but these engines generally don't go wrong at all, 200k miles is commonplace and over 300k can be found for sale regularly.

 

You can maybe remove the thermostat and from the front of the block (just behind the alternator) and disco the bottom rad hose which is connected to it, hold it up in the air, disco the coil pack and crank the engine to see if water gushes to test the water pump. I'd drain all the coolant first and do the test with fresh water, you can flush it right through, forward and back at the same time with the thermostat out.

 

It really does sound like the head gasket though, luckily it's a simple job since it's an Iron block with a SOHC 8-valve alloy head bolted onto it, tbh the cambelt and water pump are pretty simple jobs as well.

I'll order a timing belt kit and water pump and change it tomorrow.

I don't think it is head gasket though, no dips in compression, runs fine, no mayo etc, no oil contamination, no engine gasses in coolant which was the main one for me.

Tbh it would be cheaper if it was the head gasket!

They are one of the easiest hg to change haha nothing attached to the head and very little in the way. Nice four bolts on exhaust, and inlet manifolds on the top haha

Other symptoms also!

The fans in the car always blow cold

The pipe at the bottom left of the engine (the thermostat pipe) is always cold but the top right one off the rad is usually hot.

It's the pump, bad luck, I'd change the thermostat as well since they're about a fiver and it's only two M10 bolts.

Yeah, I removed the other one so the car currently doesn't have a thermostat in, needs replacing 100%.

I'll report back over the next few days with how it goes, thanks for your replies.

So got to work this afternoon changing the timing belt and water pump, nice easy job, no hard or awkward bits... Wish they could all be this easy.

Anyway, removed the water pump and hey presto, was in pieces and not attached to the pulley.