Air bubbles in coolant

[Jollywoz]

Hello all.

Getting air pressure building up in header expansion tank. Very small air bubbles drifting up in a constant stream even from cold start. It's a mk6 2.4 rwd. Recently ran out of coolant from small leak I wasn't awhere of which a spot of rad weld sorted out and this issue started straight after.

Had a new head gasket about 2k ago but is there anything else possible before it gets pulled apart again?

[metalworker0]

well you need few tools to check it properly

but first bypass the EGR cooler by connecting together the coolers inlet and outlet hoses



Tool 1
A coolant system pressure tester,

If when pumped up with a the coolant system pressure tester, if it then t looses pressure ..meaning with test started at 15 psi and goes to zero within say one min ..then there is an internal leak somewhere ..that's if if you cannot see external ones.

Possible places for hidden leaks are
1. Head gasket --- can go strait into combustion chamber and out the exhaust or into engine oil , engine oil will take on a different colour from milky white to dark mustard brown... and there will be cream mayonnaise in the rocker cover oil filler area.
2. EGR cooler
3. Oil cooler - usually leaks oil into the coolant though, but pipes to it may leak.
4. Heater core - right inside the dash ..will be noticed by wet carpets ..steamed up windows or sweet smell of antifreeze inside car.
5. Water pump weep hole
6. Coreplug rotted, hidden behind the bell housing - my last car had this ..note i don't know if a transit has such a core plug hidden away. (just checked it does not ..but check other core plugs)

if the cooling system pressure tester does not loose pressure..then there is no leak...on the static test ..and the vans own pressure cap should be checked.

if that's ok ..move onto engine running pressure test with cold engine.

other notes ..a slow weep of coolant can often be seen as a build of crusty salts at the leak point, often the same colour as the antifreeze.


Tool 2.
a compression tester

This compression tester has many diagnostic uses:

Diagnose a faulty head gasket blowing between cylinders


Tool 3 a sniff tester

or buy one of those coolant combustion gasses tester kits

INSTRUCTIONS from description


100ml Bottle ( 50ml for Tests + 50ml Free for Flushing )

- easy, fast and inexpensive way of detecting combustion leaks in cars and motorbikes.

- works with PETROL/DIESEL/LPG engines (blue fluid for PETROL, red fluid for DIESEL)

- compatible with radiators and expansion tanks

- rubber bung (bottom diameter: 31mm , 45mm - top diameter)

HOW DOES IT WORK?

When combustion leak is present, a small amount of combustion gas goes into the cooling system which can be easily detected by this simple device. In presence of these gases, the test fluid will change colour to yellow.

TEST RESULT:

If the test fluid changes the colour to:

- YELLOW, the combustion leak is present.

- STAYS BLUE, combustion leak IS NOT PRESENT during the test.

- GREEN , unclear, combustion leak could be present (50/50)

HOW TO PERFORM THE TEST:

(Before each use, flush the tester with fresh fluid )

1. Unscrew the coolant cap to release the pressure but leave it on. To avoid splashes and burns during the task, make sure the engine is cold!

2. Start the engine and leave it on for a few minutes to warm it up. (the coolant must be warm and circulating)

3. Fill the tester with supplied test fluid (2ml per test)

4. Insert the tester into the radiator's or expansion's tank inlet and observe bubbles in the chambers. You can increase the number of bubbles by accelerating the engine. Be aware that the tester is without a filter; accelerating could induce coolant droplets or fog into the device and falsify the test result. In this case, the test fluid will stay blue.

5. Don't perform the test for longer than 5 minutes. Heat is harmful to test fluid and can change the colour to green.

NOTE: Dispose of the used test fluid (even if not changed the colour), never mix it with a fresh one as it could affect the sensitivity of the whole batch.

There are other things you can spend money on ..or just wait until, one day it will fail "good style" that failure date may be days , months or years away, but if it has it in the oil ..Head gasket must be changed, if you have the faulty block, then that must be changed.

Note the above test can also be done quickly at an mot test station or garage with the emissions tester probe .

There is also a very rough test that costs nothing

The glove test
Put a rubber glove in the header tank instead of pressure cap ..if it inflates in seconds on a cold engine its the head gasket.


all the best.mark

[Jollywoz]

Thanks Mark.

Rubber gloves I do have to hand and from a cold engine starts to inflate. It's slow and took a few mins but it defo inflates.

Gasket and bolts on order I guess.

Thanks for help

[metalworker0]

No, its got to inflate in 10 seconds or so

if it inflates in mins , not conclusive proof...as that could be the coolant expanding pushing the air in the gap above it in the reservoir.

if you mark the reservoir and see that the coolant isn't rising ..then you probably have the beginnings of a head gasket failure.

all the best.mark

[metalworker0]

Do the EGR cooler bypass first

The EGR cooler

i don't know a lot about how this could pressurise the coolant, but i suppose if you have a DPF that can get clogged, then considerably more exhaust back pressure would be in the EGR cooler, for that reason i say bypass it ... inside of the EGR cooler is a heat exchanger, with thin walls separating exhaust gas from the coolant, corrosion happens over time which would cause seepage and leaks ...this could happen both ways; exhaust gas into the coolant if the DPF gets full ..or coolant into the exhaust in normal conditions..

Maybe others will chip in and say what happens to the EGR cooler as it fails.

all the best mark

[Jollywoz]

It took a few mins to inflate and I can see micro bubbles rising up thru the coolant.

Vehicle is 2002 and dosnt have an egr cooler.

Warren

[metalworker0]

OK no EGR cooler ..the rest is up to you

you can buy the parts ready ..or wait until it gets worse, more of a problem , or do it strait away

Note: this engine has the face of the cylinder head almost level with the valves, if it needs a skim it will require a thicker head gasket .

its a good time to change the camchain if it has a high mileage, that being plus 100,000


all the best.mark

[Jollywoz]

Recently had a brand new head and catching after the old one slipped and cracked the carrier. Used a 3 hole gasket then and ordered the same. In hindsight I probably shouldn't have used the old head bolts. Thought reusing once might be OK. I guess not.

Thanks for the help Mark.

Warren

[metalworker0]

You want to check everything with an engineers starlit edge and feeler blades ..including the block face .

best value - versus thickness / length etc

18 inch is what think you need

https://www.bearingboys.co.uk/Engineers ... n-321541-p

£30.22

make sure it comes in a case!

all the best.mark