Intercooler Cleaning: Oil in Intercooler & What Never to Wash It With

Is your turbo engine losing power? Do you have oil in the intake hoses? Then it is time to look at the intercooler. This guide explains what the intercooler does, where the oil inside it comes from, how to clean it the right way and, most importantly, what you must never wash it with. Everything is shown with a 3D intercooler model.

Video: Intercooler Cleaning: Oil in Intercooler & What NEVER to Wash It With (3D Animation), 4:32 min, by Auto Oprema. The video has English and Serbian audio (choose the audio track in the ⚙ settings) and subtitles.

Quick answer: how to clean an intercooler

Clean the intercooler after every turbo repair or replacement and every 50,000–60,000 km.
Never use diesel, gasoline, harsh solvents, brake cleaner, oily degreasers or boiling water.
Use a dedicated intercooler cleaner (or warm water at 40–50 °C with a mild, water-soluble degreaser that is safe for aluminium), rinse with warm water and dry it completely.
Always find the cause of the oil: check the turbo and the crankcase breather.

What does an intercooler do?

When the turbo compresses air, the air heats up. Hot air is thin: it carries less oxygen, and the engine loses power. The intercooler is a heat exchanger between the turbo and the intake manifold. Hot air flows through its thin aluminium tubes, the fins pass the heat to the outside air, and cool, dense air goes into the engine. More oxygen means better combustion and full power.

Where does the oil in the intercooler come from?

Source	What happens	Is it normal?
Crankcase breather	Oil vapour from the crankcase is sent into the intake before the turbo.	A little oil is normal. If the breather membrane is worn, much more oil gets through.
Worn turbo	When the turbo seals leak, oil goes straight into the boost pipe.	No – the turbo needs repair. See how to check a turbo.

In both cases the oil settles at the bottom of the intercooler.

Why oil in the intercooler is a problem

Oil and dirt clog the tubes and reduce cooling and airflow.
Symptoms: loss of power, boost pressure errors and problems with the MAP sensor.
On a diesel, a large amount of oil can even be sucked into the engine and cause a dangerous engine runaway.

Where is the intercooler and how to remove it

The intercooler usually sits at the front of the car, between the A/C condenser and the engine radiator. Loosen the hose clamps on the inlet (from the turbo) and on the outlet (to the intake manifold). Full removal gives the best result, but on many cars you can also clean it on the car, through the lowest hoses.

What you must never wash an intercooler with

Do not use	Why
Diesel	It leaves an oily film that cannot be dried. Dust and soot stick to it, so the intercooler clogs again even faster.
Gasoline or harsh solvents	They can damage the rubber hoses, the seals and the protective coating.
Brake cleaner	Never use it for this job.
Oily degreasers	They leave residue, like diesel.
Boiling water	Avoid it.

What to use instead

Warm water at 40–50 °C with a mild, water-soluble degreaser that is safe for aluminium works. The best solution is a special intercooler cleaner: it dissolves oil and sludge quickly, it is safe for aluminium, plastic tanks and seals, and it rinses out completely without leaving any residue.

How to clean an intercooler: step by step

Plug the lower opening and pour the intercooler cleaner in through the top.
Fill the core completely and gently rock it to remove air pockets.
Let it soak for 20–30 minutes, or longer if it is very dirty.
Drain the dirty fluid into a container and dispose of it properly.
Rinse at least twice with clean, warm water until the water comes out clear.
Dry it completely: blow compressed air through the intercooler until no water is left inside. If you clean it on the car, protect the alternator and the electrical parts.
Leak test: fill it with water, mark the level and wait. If the level stays the same, it does not leak.
Reinstall it and tighten all clamps well to avoid boost leaks.
Find the cause of the oil by checking the turbo and the crankcase breather.

Summary

Clean the intercooler after every turbo repair and every 50,000–60,000 km.
Never use diesel, gasoline, brake cleaner or boiling water.
Use a special intercooler cleaner, rinse with warm water and dry it completely.

Video chapters

0:00 – Power loss and oil in the intake hoses
0:15 – What the intercooler does
0:53 – Where the oil comes from: breather and worn turbo
1:09 – Why oil in the intercooler is a problem
1:43 – Where the intercooler is and how to remove it
1:59 – What you must never wash it with
2:30 – What to use instead
3:03 – Cleaning procedure step by step
3:36 – Drying and leak test
3:52 – Reinstalling and finding the cause
4:09 – Recap

Frequently asked questions

Is a little oil in the intercooler normal?

Yes. The crankcase breather sends oil vapour into the intake before the turbo, so a little oil in the intercooler is normal. A large amount points to a worn breather membrane or leaking turbo seals.

Can I clean an intercooler with diesel?

No. Diesel leaves an oily film that cannot be dried. Dust and soot stick to it and the intercooler clogs again even faster.

How often should an intercooler be cleaned?

After every turbo repair or replacement (this is mandatory) and every 50,000–60,000 km.

Can I clean the intercooler without removing it?

On many cars, yes, through the lowest hoses. Full removal gives the best result. If you clean it on the car, protect the alternator and the electrical parts.

What problems does a dirty intercooler cause?

Loss of power, boost pressure errors and MAP sensor problems. On a diesel, a large amount of oil can be sucked into the engine and cause engine runaway.

How do I check the intercooler for leaks?

Fill it with water, mark the level and wait. If the level stays the same, it does not leak.

Related 3D diagnostics guides

How to Check a Turbo – oil leaks, shaft play, blade damage and when to repair or replace the turbo.
False Air / Vacuum Leaks – symptoms of unmetered air and 4 ways to find the leak.
Crankshaft Position Sensor Test – no start, stalling when hot, limp mode and 4 tests for the CKP sensor.
How to Test a MAF Sensor – power loss, high fuel consumption and 4 tests before you buy a new sensor.
Clogged EGR Valve – black smoke, rough idle, how to test the EGR and clean it properly.
Catalytic Converter vs DPF vs FAP – what each exhaust part does, lambda sensors and DPF regeneration.

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