Tip & How-To about Audi A4
If you own a Volkswagen or Audi and have coolant in your engine oil or oil in your coolant you may have a failing oil cooler. This may have been misdiagnosed as a bad head gasket.
Before spending hundreds or thousands repairing a head gasket that may not be the problem you can perform this relatively easy check of your oil cooler which is a common problem on many Volks/Audi models that use oil filter type of oil cooler. This type of cooler is located between the oil filter and the engine block. The oil filter screws onto the oil cooler. It has two rubber coolant hoses attached to it and is made from aluminum.
The oil cooler works by passing engine oil through the body of the cooler. The engine oil passes over what resembles a radiator inside the cooler. This 'mini radiator' is passing engine coolant in through one of the hoses and out through the other. When working properly the oil and coolant is kept separated. Over time the passages inside the cooler can corrode and the oil and engine coolant inside can mix. This can lead to coolant in your engine oil (which may produce a milky substance on the inside of the oil filler cap) or oil in the coolant (which you may be able to see in the coolant reservoir as a dark ring or oily film).
To test your cooler for leaks you will need a few basic tools and about 3 hour of your time. (To allow for the engine to cool)
-Basic ratchet set and set of screwdrivers.
-One straight 5/8 inch plastic heater hose connector. You can find this at most auto parts or plumbing supply stores. Cost about $1.
-A pan to catch some coolant that will spill.
This procedure is best done on a lift but can be done using jack stands as well. This MUST be done with a cool engine to avoid burns from coolant.
-Lift or jack the front end of the car. (If you don't know how to safely jack a car onto jack stands, DO NOT proceed any further. Take the car to your repair shop and have them follow these instructions)
-Remove the plastic cover under the front of the car (if your model has this) to expose the oil filter. The oil filter is a cylindrical part that sticks out from the side of the engine.
-The oil filter is screwed into the oil cooler. You will see two rubber hoses connected to the oil cooler.
-Using a flat screwdriver or socket loosen the clamps connecting the hoses to the cooler. Now have the plastic connector handy. Remove the hoses from the cooler, you may need to pry on them with a screw driver. I find that twisting them to break their seal works well. Catch any coolant that spills in the pan.
-Take each rubber hose and push them onto the plastic connector being sure to keep the clamps on the hoses. Tighten the clamps. (Not too tight, just snug) Now you have just eliminated the cooler from the system temporarily. The rubber hoses are now connected to each other.
-Wipe the oil cooler clean with a rag so it is easier to see any leaks that might develop.
-Now start the engine and let it run to normal operating temperature. This means at least 15 minutes but to be sure you find any leaks I suggest half an hour.
-Keep a close eye on the 2 metal tubes on the oil cooler. (The ones you removed the rubber hoses from) You are looking for engine oil to begin seeping out. It will appear golden brown to black in color.
If you see oil coming from those tubes you have found your problem. You will need to buy and install a new oil cooler.
If you don't see any oil leaking you will need to look elsewhere for the trouble. Possibly a head gasket, unfortunately.
-Let the engine cool for a few hours before reattaching the oil cooler. It is the reverse of removal.
-Replace any lost coolant with the same amount you caught in the pan.
And there you have it. A pretty simple procedure that may save you a bunch of cash in repairs.
Posted by badbrains on
Jun 20, 2012 | 2000 Audi A4
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