Flushing/whooshing sound on start up - DIY air bleed

CiaranMcK · June 22, 2022

Hi,

I’ve noticed a water flushing sound behind the dash on start up. The water pump is fairly new so I’m guessing air in the system. The expansion tank is full so I don’t think I’m losing any coolant and so far I’m not getting any overheating but it’s still not ideal.

I’ve seen references to running the car for half an hour with the cap off to rid the system of air. Can someone give me a walk through of how I do this? Which cap I remove, if I could do with any equipment etc? I also have a sloped driveway, so I’m guessing nose up would be best?

I don’t just want to run in there all guns blazing and mess up.

Thanks in advance!

CiaranMcK · June 22, 2022

1 hour ago, CiaranMcK said:

Hi,

I’ve noticed a water flushing sound behind the dash on start up. The water pump is fairly new so I’m guessing air in the system. The expansion tank is full so I don’t think I’m losing any coolant and so far I’m not getting any overheating but it’s still not ideal.

I’ve seen references to running the car for half an hour with the cap off to rid the system of air. Can someone give me a walk through of how I do this? Which cap I remove, if I could do with any equipment etc? I also have a sloped driveway, so I’m guessing nose up would be best?

I don’t just want to run in there all guns blazing and mess up.

Thanks in advance!

Correction, expansion tank is nearly empty when cold

ahmed24 · June 23, 2022

The expansion overflow bottle should not be empty. This is what is causing air to enter your system. Top-up to near the full mark with pink super long life coolant when cold and then monitor the situation over a few long drives. If there is air in the system you can burp them. Hopefully you don't have an airlock anywhere. If there's not much air in the system then the overflow expansion bottle should always be at a consistent level. When engine cools the coolant shrinks and the volume of coolant in the blocks reduces and hence it sucks from the overflow bottle. If overflow bottle is low then it will just suck air in.

normski2 · June 24, 2022

I changed my water pump and serpentine drive belt about 4 weeks ago. Did the whole job on the drive. My drive slopes too, downwards. I had completed the task with nose down and went through the normal warm up procedure.

At this point I found that even with temp set to high and fan on full blast the air in the cabin was not coming through hot at all. Turned the car around with nose pointing uphill and it was sorted within 10-15 mins.

As Ahmed has pointed out the expansion tank should not be empty!

J Henderson · June 26, 2022

Hi @normski2

Was changing the pump a preventative measure, or had it failed? And how many miles on your car?

I'm thinking this is a job I'll probably have to face in the very near future.

normski2 · June 26, 2022

Hi John

It was purely preventative. I was approaching 100,000 mls so felt it was appropriate. There was no record of it being done on any of the service history that I have, and I've had the car from 30,000mls. So I'm confident it was the original pump.

I figured it wise to renew the serpentine drive belt whilst I was doing the pump. The belt has to come off as part of the procedure anyway. Those parts cost me about £93 all in, I had bought them a year ago prior to retiring ( pump was a Blueprint make). Can't remember how much the pink coolant was but you'll need 2x5ltr pots as you'll need close to 9ltr for the fill up.

I'm pretty competent with spanners but like to take my time and be thorough. All in it took around 4 hours. You'll need catch pots as it gets quite messy when you pull off the old pump. The old pump was in really good condition. Bearing was silent and there was no external seepage or crust anywhere.

One thing I will say is you'll need a 3/8" drive socket set to be able to get in there, a 1/2" set is no good on the pump bolts as the std drive extension is just too long.