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Hey,

I've been driving around without a front bumper for a while now and noticed this spot on my intercooler getting slowly bigger. Is this a leaky intercooler or just getting dirty from driving around? Pic attached

Thanks for the help!
 

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looks like a grease spot. hit it with brake clean and see if it comes off
 

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You are right to suspect intercooler integrity, especially if you notice the dark area growing and there are no other sources of grime/oil/grease near this location. Make sure you don't have any pinholes from your radiator, A/C condenser, etc. that are directing fluids/oils very very slowly in a small stream toward this spot.

If nothing obvious leaking is nearby, easy way to check the cooler is to fab up a leak check device.

For an intercooler of your size, I have built caps to cover the intercooler ends using the silicone couplings you already use for your aluminum charge air piping, and PVC household water drain/supply pipe and components from a hardware store (a short straight section with threads on one end of the pipe and a matching threaded cap or glue the cap to the straight section if no threads).

You can then drill a hole into the cap and use a high pressure tire valve stem purchased from an auto parts store. These valve stems stick through the hole and have a rubber seal on the inside part of the stem, with a locking nut to pull the valve stem against the cap creating a seal. You can build two of these guys for around $15 with locally sourced parts.

Once you have these pieces built and clamped to your intercooler, you can use a cheap bicycle pump or a walmart 12V tire air compressor that has a pressure gauge that reads live tire pressure on it for like $5.

With the silicone hose clamps tightened securely to your adapters and the intercooler, pressurize the assembly to 15-20PSI, shut the compressor off and watch the gauge for leakdown.

If the gauge leaks down quickly, troubleshoot for leaks with a squirt bottle filled with water and dish soap to make bubbles. Check all of your clamps/fittings/seals for leaks first. If those are not leaking, start spraying down the intercooler everywhere or submerging it underwater (bathtub or bucket) and watching for bubbles to form while maintaining a consistent pressure.

Ta-da! $20ish homebrew intercooler pressure tester! This will prove if the intercooler is leaking.
 

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there shouldn't be anything in the intercooler to leak though.......0_o
 

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there shouldn't be anything in the intercooler to leak though.......0_o
You would definitely think the charge air components should solely contain AIR, nothing else. It makes sense!

Except, there can be very small "trace" amounts of oil present in the pressure tract, depending on the turbo type (ball bearing cartridges use significantly less oil than journal bearing CHRAs), intake/exhaust design, pressure levels being run and overall turbo health. A quick inspection of the charge air piping between the compressor housing and the inlet (hot side) of the charge air cooler will normally reveal a very very thin oil film buildup on the walls of all things that pipe the pressurized air to the throttle body/intake manifold.

This is very normal for a very small amount of oil to be present in the charge air tract. Turbo center housings can't be sealed by rubber type seals effectively because of the harsh conditions they would be subjected to, and instead they use tight fitting precision machined high quality metal components everywhere and rely on the precision fit to keep oil movement from the center housing to the turbine/compressor housings at a minimum.

Some oil does end up making it past these precision parts, but turbos do have another trick up their sleeves for further keeping oil escape to a minimum: housing pressure equilibrium. It is known that the pressure in the compressor housing is roughly equal to what is present in the turbine housing, and these pressures will follow each other as charge air gas volumes and pressures change.

For example, if normal boost for you is around 20PSI, then the exhaust gas pressure existing between the exhaust valve and the turbocharger exhaust turbine wheel during the exhaust stroke is roughly also 20PSI. The fact that these pressures stay more or less equal to each other, means that any oil trying to push past the shaft sealing device towards the housings is going to have a harder time vs just simply heading for the turbo drain port.

Perfect pressure equilibrium between housings does not exist under every operating condition, let alone the pressure pulses experienced within the intake and exhaust tracts. One housing will almost always be higher or lower than the other with this shifting around continuously, but more or less always pretty close to each other. Because of turbo oil sealing techniques, pressure differentials and the insane volatile environment turbocharger components are subject to almost guarantees a small amount of oil escaping.

It's not a perfect system, but these sealing techniques do a damn good job for the conditions turbos are up against.

Because of the small traces of oil that can be present, if your intercooler DOES have a super tiny pinhole in it on a normally driven in-service vehicle, over time you will notice a dark spot slowly getting larger as grime/dirt/dust end up sticking to the oil that does seep out. The same thing happens with pinholes in radiators, oil coolers, A/C condensers, etc. a dark spot slowly appears on a normally clean looking aluminum component!

It's less likely to do this with coolant, because oil doesn't evaporate and grabs dirt like a magnet!
 

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I just thought of a service bulletin when I was a tech in the medium/heavy duty truck industry. Every OEM has some kind of bulletin like this for just about any turbocharged vehicle that explains what normal vs abnormal oil presence in the intake system looks like. I actually still had this in my old work archives! It provides a great description of what is normal oil carryover vs excessive/abnormal oil carryover for your average journal bearing turbocharger. It also explains what causes this oil carryover.

I have attached the screenshots to this post for your viewing. You might notice that on the ones that say "normal" there is actual pooling of oil present! That takes a LONG time to get to that level. Most of the normal carryover oil in the intakes on these Hino vehicles ended up collecting in the intercooler, and they would coke up internally and need replacing after 500,000ish miles. These intercoolers are about the size of a civic hood, and had lots of oil holding capacity lol.

You would constantly see oil traces around all of the silicone couplings, because of the "accordion" bendy parts designed into the coupling oil loved to pool right there after a while. If customers complained about the oil around the joints, the official "procedure" from the OEM was to clean all the oil off, add high quality oil resistant liquid silicone to the hose mating joint and reclamp the coupling really tight!

As much oil passed through these intake systems, not one of them would ever smoke out the tail pipe under WOT snaps and full boost, even on pre-exhaust aftertreatment engines! It just goes to show you how slowly the oil actually moves through the system.

It does accumulate normally in low points within the intake tract on all kinds of vehicles. The amount pooling up of this oil is much less noticeable on smaller charge air systems because the air velocities are usually a bit higher than on large volume charge air systems for larger engines.

Normal Oil Carryover



Causes of Excessive Oil Carryover



Excessive Oil Carryover
 

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