Coolant Leak at Water Bypass/Thermostat

As I am due for a routine oil change, I opened the cap to find the dreaded chocolate milk oil coating the underside of the cap. Although my truck (06 DC SR5 4.7L) is currently asymptomatic, I definitely need to address this issue and fix its source, which I am really hoping is not the head gasket. I have found some dried up pink spots on the water bypass joint under the connection to the thermostat and I'm wondering if this is the culprit. Does anyone know if this is an area that could cause leakage into the oil system or if this is a completely unconnected / independent coolant loop? Due to the clear leak of coolant being at the same time as my milky oil, they sure seem to be at the very least correlated.

Additionally, I recently (about 3 months ago) had my radiator, water pump, and timing belt swapped out in a shop. I had these swapped out due to an overheating issue in the late summer which was diagnosed to be an old clogged up and leaky radiator. I would say that the overheating could have caused some issues to different gasketed connections in the cooling system, but I have not had any signs of the pink coolant on the water bypass joint until now.
I do not think there is a way for the rad and pump swap to introduce coolant into the oil, can someone confirm?

I plan to change the oil, fill the coolant reservoir, and clean off the leaked coolant, then closely monitor for a few days.

Any tips would be greatly appreciated. Current photos are attached.

 

I hate to say it, but that doesn't look good.

 

Not good like "head-gasket replacement not good"? Do you think an oil change, coolant fill, cleaning, and monitor is the best solution for the next couple of days?

 

Yes my thought was head gasket when I saw the oil cap picture. I'm not an expert though. I'm going to tag @empty_lord, or resident Toyota mechanic.

 

Could be normal based on the climate it’s operating in.
https://www.youtube.com/watch?v=nYprcmsG-FA

 

Hmm. I missed this.


Do you do a lot of short trips by chance? Condensation like that isn’t unreasonable if the truck takes many short trips


The leak physically cannot leak into oil from there, that part is just purely cooling system. Get it addressed, but basically, when the t belt was done someone didn’t properly seal it.

 

I had a '88 Chevy Blazerette with the 4.3 engine and had the same, I had the same bad gut feeling. The oil fill tube was 4" or 5" long and the highest point of the engine which is a natural point for steam to collect. the neck was easy to remove on mine and I was able to put the cap straight on the valve cover and never saw it again. We had that vehicle for 200K+ miles and sold it to another gentleman who was still driving it when we moved from the area. I think on later models GM put a vacuum line up there to keep it burn the moisture and keep them clean.

 

Update and [hopefully] good news!

I changed the oil last night and it looked fine. Dark, smooth, and clear just like used oil should look. Before the change, there was still some of the foamy chocolate milk under the cap, but the dipstick and oil were as they should be. Addressing the overheating issue, this was over the summer and I had a boil out on the radiator. What I'm hoping is that when the coolant splashed everywhere I had some collect on the thermostat/bypass joint and it went unnoticed until now. This boilover was at idle in the heat of summer, and I'm hoping the radiator's relief valve did its job and I don't have cracking of the block/head or a blown gasket. I cleaned up the dried coolant and wiped down the engine bay; I plan to keep an eye on this.

Funny you mention this... I actually switched jobs so I have a very short 1.5 mile commute each day, so my truck has been running high quantities of short trips compared to normal. I'm hoping that this is a natural amount of condensation. Is this seen more frequently in vehicles with shorter drives?

 

Water condensation is exactly what that is you see. I get it all the time. My commute is 5 miles via interstate so by the time I just get into work, the truck temp is where it needs to be but unfortunately, I need more mileage to burn off the condensation. I've had my oil cap filled with what I call the "mayonnaise" effect.

Just change your oil regularly or drive further/longer to burn it off (if you're able).

 

Thanks for the help Jack and everyone else! The old truck had me pretty worried when I first saw the infamous choco milk but I will just keep the engine clean and monitor routinely.

 

Yeah that effect usually shows up the most in cold weather when you don't get the opportunity to get the engine up to temp after a drive.

 

Yup, that’ll do it

 

I get the brown froth in oil cap every winter, have for 8+ years. its just naturally occurring moisture that isn't getting fully burned out of the oil. Especially common if you only do short trips (which I often do) and/or live in an environment with cold and humid conditions. I like to think the long filler neck further from engine heat was done on purpose to collect the moisture for easy cleaning... You're not the first one to freak out when first seeing it, I almost shit a brick! fear not, its common.