Creamy substance in expansion tank (SOLVED)

Hi everyone after finding some creamy sludge in my TD4 fl1 expansion tank I decided to replace the oil cooler for a new one. I have no bubbles in the tank, no white smoke, no coolant loss, no oil loss, im hoping its not the hg but cant be sure. Afyer fitting the new cooler Ive flushed the system a couple of times and replaced the expansion tank as it was cracked , I still have droplets of what looks like oil coming through thw return hose to the tank which ends up with a the same gunge floating on the top of the water. Am i kidding myself that its something else is is it the hg that has failed ?

Might need to remove expansion tank and clean it out a few times till slugs is no more

Many thanks im trying some dishwasher tablets tomorrow so onwards and upwards

I'm still cleaning mine out occasionally, 3 years after replacing the oil cooler.

Wow ive got a long way to go then ! Im gonna try a tester this week just to see if there are any fumes in the expansion tank that might point to a head gasket but hope its the oil cooler ive re placed

When i clean my coolant out i prefer to keep washing water through until it goes clear, before dropping all the liquid out. This helps wash anything out which is in the coolant like oil.

I disconnect the lower hose on the coolent reservoir and block the hole in the reservoir. Then direct the pipe to a bucket. Then keep filling the coolant reservoir to the top when the level drops. Level will drop as the higher water will push through via gravity. When my output pipe to me bucket runs clear i know the coolant and any nasties are washed out, if possible. It doesn't wash the whole system through but it does part of it. So makes me happier. I can also see what comes out. I then empty the contents of the cooling system and continue as normal.

Hippo said:

When i clean my coolant out i prefer to keep washing water through until it goes clear, before dropping all the liquid out. This helps wash anything out which is in the coolant like oil.

I disconnect the lower hose on the coolent reservoir and block the hole in the reservoir. Then direct the pipe to a bucket. Then keep filling the coolant reservoir to the top when the level drops. Level will drop as the higher water will push through via gravity. When my output pipe to me bucket runs clear i know the coolant and any nasties are washed out, if possible. It doesn't wash the whole system through but it does part of it. So makes me happier. I can also see what comes out. I then empty the contents of the cooling system and continue as normal.

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Many thanks hippo I appreciate the help, so I understand I disconnect the lower pipe on the expansion tank that goes to the pump, then block the outlet nozzle on the tank. Then ?? At this point im a bit lost sorry.
I did try directing the return pipe to the tank into a bucket and kept topping up the expansion tank while running the car, it did clear some out but still very murky woth what looks like droplets of oil but cant be sure, so feel i need to find another method of flushing. Can you go through your method again mate so I fully understand cheers

Flush the system out using orange juice, this is a tip that's been used on the R40 engines.

(Best tip of all time, 50/50 water to pure orange juice without bits, run up to temperature, then drained whilst quite hot & any contamination is in suspension.
This gets rid of all emulsified oil deposits, safely follow this by a fill of clean water run up to temperature, then dump it out, then fill with 50/50 antifreeze water mix.
Works every time)


Steer clear of Dishwasher detergent (sodium metasilicate) is quite alkaline, pH 11-12 I'd guess). Aluminium is dissolved by alkaline solutions generating hydrogen gas. (Ever put something aluminium in the dishwasher?) If you got a good head of hydrogen in the system it could make quite a bang when you removed the filler cap, you don't want anything foaming in the system.

Arctic2 said:

Flush the system out using orange juice, this is a tip that's been used on the R40 engines.

(Best tip of all time, 50/50 water to pure orange juice without bits, run up to temperature, then drained whilst quite hot & any contamination is in suspension.
This gets rid of all emulsified oil deposits, safely follow this by a fill of clean water run up to temperature, then dump it out, then fill with 50/50 antifreeze water mix.
Works every time)


Steer clear of Dishwasher detergent (sodium metasilicate) is quite alkaline, pH 11-12 I'd guess). Aluminium is dissolved by alkaline solutions generating hydrogen gas. (Ever put something aluminium in the dishwasher?) If you got a good head of hydrogen in the system it could make quite a bang when you removed the filler cap, you don't want anything foaming in the system.

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Thanks m8 I'm gonna give this a try it sounds great so will let you know how I get on later today thanks again

It's difficult to get oil out of the cooling system. Oil doesn't dissolve in water, and sticks to the cast metal surfaces of the block. Also oil is viscous (thick) when cold, and only gets less viscous when the engine is at running temperature. This make removing it a difficult and slow process. Flushing with a garden hose works to a degree, but the water is cold and so it's flushing ability is reduced.

After the initial clean, over time the oil in the system slowly migrates to the expansion tank in use. This can then be cleaned out regularly. I've found that I don't need to clean it so often (every 6 months), as time has gone on.

Nodge68 said:

It's difficult to get oil out of the cooling system. Oil doesn't dissolve in water, and sticks to the cast metal surfaces of the block. Also oil is viscous (thick) when cold, and only gets less viscous when the engine is at running temperature. This make removing it a difficult and slow process. Flushing with a garden hose works to a degree, but the water is cold and so it's flushing ability is reduced.

After the initial clean, over time the oil in the system slowly migrates to the expansion tank in use. This can then be cleaned out regularly. I've found that I don't need to clean it so often (every 6 months), as time has gone on.

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Thanks Nodge I'll keep up.with the monthly flushes till it gets better. Great advice as always

I've used Jizer and that worked great to clean up the oil. Obviously only need to run to warm and get it running through system for a short time then drain and flush a few times with water.

Oh and removing the thermostat is going to make your life easier. otherwise you'll not be able to circulate the whole system effectively.

John5710 said:

Many thanks hippo I appreciate the help, so I understand I disconnect the lower pipe on the expansion tank that goes to the pump, then block the outlet nozzle on the tank. Then ?? At this point im a bit lost sorry.
I did try directing the return pipe to the tank into a bucket and kept topping up the expansion tank while running the car, it did clear some out but still very murky woth what looks like droplets of oil but cant be sure, so feel i need to find another method of flushing. Can you go through your method again mate so I fully understand cheers

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No. Remove lower pipe from coolant reservoir and point towards a bucket to empty into. Block the coolant reservoir hole you just pulled the pipe oft. Now tip water into the expansion tank to fill to the top, via the hole covered with the screw on cap. The pressure will push the water and coolant through the system and out via the pipe into the bucket. Keep topping up the coolant reservoir until you see clear water flowing out.

It's not a perfect process to get everything out but it does allow you to wash the coolant out and anything in it to a certain extent, before disconnecting the big pipes to drop all the water out of the radiator etc. I do mine this way as I choose to but there are other ways. As above you can force water (cold or hot) through it via a hose and use chemical or other diy method. Put the hose in the coolant reservoir and block the rest of the hole with a rag. I would never put a harsh cleaner through myself as cleaning that out is difficult anorl. Opinions vary on the different methods. You can also hose the radiator out. Don't use pressure washers like on you tube as they're too powerful/harsh. Make sure you know how to bleed the air out when refilling.

windy81 said:

Oh and removing the thermostat is going to make your life easier. otherwise you'll not be able to circulate the whole system effectively.

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You can't remove the thermostat on a TD4, as it's an integral part of the housing.

oh well then it's a bit more difficult to do

Hi everyone I flushed my system again and again, and it does look better but still showing signs of oil deposits. However my hg test kit arrived today so gave it a try it out and it now looks likely my hg is at fault.
It took approx 3 mins for it to turn from blue to green so it looks like my initial fears are now realised so decisions decisions, do i let the garage do it (gulp) or attempt to tackle it myself ? On the haynes manual it looks a bit daunting for a diy mechanic but any advice would be appreciated.

John5710 said:

However my hg test kit arrived today so gave it a try it out and it now looks likely my hg is at faul

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That's a first for here. The TD4 isn't known for HG failure. I don't mean it can't happen, but it really is extremely rare.

Those colour changing dyes aren't very accurate anyway. They react with combustion byproducts and change colour. However on a diesel, if combustion byproducts are getting into the coolant, you wouldn't need a dye to prove it, as the coolant will be ejected at high pressure through the pressure cap, or by exploding the coolant tank.

I expect the dye it's showing a failed HG because there are byproducts of combustion in the oil that contaminated the coolant.

I'd ignore what the colour of the dye is saying, as it's very very unlikely to the HG on a TD4.

Nodge68 said:

That's a first for here. The TD4 isn't known for HG failure. I don't mean it can't happen, but it really is extremely rare.

Those colour changing dyes aren't very accurate anyway. They react with combustion byproducts and change colour. However on a diesel, if combustion byproducts products are getting into the coolant, you wouldn't need a dye to prove it, as the coolant will be ejected at high pressure through the pressure cap, or by exploding the coolant tank.

I expect the dye it's showing a failed HG because there are byproducts of combustion in the oil that contaminated the coolant.

I'd ignore what the colour of the dye is saying, as it's very very unlikely to the HG on a TD4.

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Thanks Nodge mate you have just made my day, the car runs like a dream so your explanation couldnt have been better times as I have just read exactly the same from similar chemical dye tests. So I agree they arent to be trusted I will now momitor the coolant tank as it does look 100% better after a couple more flushes, and thanks again your advice is very much appreciated.

Is the oil creamy? Is there cream around the inside of the oil filler cap?