New radiator was installed yesterday, because of severe leak. Radiator was topped off with coolant. White milky film observed in old radiator: mechanic indicates that this oil that has infiltrated the coolant system and that there is a leak in the engine.

After install, car was driven 4 miles and parked for 3 hours. Took the car out for a drive and pegged (overheat) the temperature gauge at mile 2 and was summarily turned off to prevent damage.

Attempts to refill coolant showed that it was down at least one gallon. Took the vehicle back to the mechanic at Advance Automotive and could not find the leak. Any guidance / tips to track down the leak are appreciated. Seriously considering a borescope because it is hard to see items.

Diagnostic questions are also appreciated: thank you

Update: I am building a tire-valve radiator adaptor per this instruction: the intent is to pressurize the fluid with the hope that it will spurt fluid to locate the leak instead of the current slow trickle

  • Has the coolant level dropped since the second refill of coolant?
    – mikes
    Nov 28, 2016 at 11:27
  • Last night (day 2 after radiator install), a spot-check in garage confirms a slow leak persists. This leads to concluding that a leak must be found and corrected. This issue is separate from oil infiltration in the old radiator?
    – gatorback
    Nov 28, 2016 at 17:16

1 Answer 1


Finding oil in the coolant system most often means a broken head gasket. There is a tester that you can use to see if this is a problem, which costs $35 or so. Amazon has one here:


But you can find a similar tester in most auto parts stores. Basically it will show if there are combustion gasses getting into the water cooling system. Although this is not a direct measure of oil getting into the water, a blown head gasket is usually the most common cause of oil in the coolant.

  • Nice. Ordered the Amazon Combustion leak detector today. Seeking guidance on how to find coolant leak.
    – gatorback
    Nov 29, 2016 at 1:52

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