Deton8r

So a couple months ago, I changed out the intake manifold gasket (upper and lower) on my 2008 JK. A couple weeks later, I had to replace the water pump. After doing the water pump, I saw coolant pudding on the floor and figured I did a bad job sealing the water pump so I added some UV dye to the radiator. This allowed me to find my leak, which sure enough was the water pump gasket. As it turns out, one of the bolts did not hold torque and was only a bit more than finger tight. Needless to say, I retorqued all the water pump bolts and the leak went away. We've been driving the Jeep ever since and even took it on a 1500 miles trip to MS from FL a few weeks ago.

The other night, another puddle of coolant was on the ground. I grabbed the UV light and checked around everything I could find. I think it may be leaking in a couple of places, like the thermostat housing and temperature sensor. The most troubling part, and the reason for my post, is I saw the UV dye in the engine oil. First on the dipstick, then I pulled the filler cap and saw it inside the valve cover, too.

What are the chances I failed to properly clean the mating surfaces well enough on the intake manifold job? I thought I did a good job but I did it all by hand with brushes and scotch bright pads. I didn't use any locktite on the intake bolts so could they have come loose? I'm really hesitant to pull the intake and redo the job if it might be something else. Anyone have an idea of something else it could be? Is the water pump able to somehow leak internally? I figured it would be sealed off from the internals. I also thought maybe head gasket/s but the Jeep has never overheated.

Any ideas would be appreciated. Thank you!

SoK66

When something like this occurs after a repair it's always best to visit the last thing that was done before moving on to another possibility. Coolant in the engine is bad juju, so I would drain the oil ASAP. The intake manifold reseal looks to be a PITA, I understand your reluctance to visit the job again. Beforehand, try pressurizing the cooling system and look for leaks with your UV light. If the pressure drops but is not visible externally, then you know you have an internal leak. If it's the manifold the coolant will leave a tell tale trace that should pinpoint the leak.

FWIW, the intake manifold on. 3.8L can be difficult to seal. Several videos on You Tube on the subject.

Mr.T

If there's UV dye in the oil, but no other sign of coolant in the oil, it might be worth checking some of the same unused oil with a UV lamp just in case it has some fluorescence -- Not something I've seen, but never checked either. If a shop (or prior owner) added dye to the engine oil to check for an oil leak, some might still be left over from that too. Another idea is to send an oil sample to Blackstone, Amsoil, etc. and note that you're checking for coolant in oil. And like SoK66 wrote, changing the oil is high priority -- Check with the UV light right afterward, and keep checking.