Antifreeze in oil, blown head gasket or oil cooler?

04’ Tundra 188k miles
DC 4.7 V8 4x4 SR5

Symptoms:
Losing coolant with no visible leak

Performance: Runs great with enough coolant but eventually overheats, runs fine again once topped off. Idles fine, no misfires, no noticeable loss of compression or power/mpg

No smoke from engine or exhaust.

Changed the oil yesterday after the truck overheated on a trip. I wanted to see what the oil looked like. I caught much more “oil” than the spec’d 6.5 qts. It overflowed a 7qt pan by a good amount even before pulling the oil filter. The oil was dark(black/brown) and very runny. I believe antifreeze is getting into the oil.

I did find the creamy milkshake on the oil cap a couple of weeks ago, I suspected it may have been due to moisture in the engine, since I’m pretty sure the engine bay was pressure washed prior to being sold. I wiped it off, kept driving and have not seen it since.

No visible oil inside radiator/coolant reservoir.

When bleeding the cooling system after topping it off I notice no bubbling at the radiator other than the initial air pocket.

from my understanding:

the combustion chambers run at a higher pressure than the cooling system. Thus, if a head gasket or cylinder was leaking then there would be oil inside the antifreeze.

I believe, at the oil cooler, the oil pressure is lower than the cooling system. So, if there was an internal leak here, this allows antifreeze to flow into the crankcase.

recent engine work includes:
the timing belt and water pump (done by indy shop)

in either case:

the head gasket is $100 but takes way more labor.

the oil cooler is $1000 but less labor involved.

I haven’t pressurized the cooling system or done any compression testing yet.

this is above my pay grade and I’m going to take it to the garage tomorrow.

 

Combustion chamber to coolant doesn't leak oil, but it does overpressure the coolant with exhaust. (which causes overheating

Crankcase to coolant, leaks coolant to oil (crankcase is usually at NEGATIVE pressure, while coolant is at 18kpa)

re-check for bubbling, with someone holding the engine at about 3K RPM. Many times HG's won't leak at idle until they are really bad.

To my knowledge there is no oil-coolant intercooler on our trucks.

There is an ATF-coolant intercooler in the radiator and additional air-ATF cooler on some..

 

Filter housing has a water pass-thru on the 2UZ, the unlabeled part. The two doohickeys are water passthru. @Tundra2 posted pics of his because it was leaking, I think, he posted about it in crackhead res.:

​

 

Oil and water/coolant mixing make oil a creamy chocolate milkshake consistency. If your oil is brown/black (looks like oil, not a McDonalds milkshake) then I don't think you have coolant mixing with it.

 

This is normal, shy of a slight overfill situation, but half a quart isn't enough to do damage. I was actually closer to 6.8qt during my last OC cycle.

This is a symptom of short trip driving, failure to get to operating temp long enough, and steam condensing in the crankcase top-end. It's documented well on this forum and is not sign of HG leak.

 

https://parts.priceleblanctoyota.com/oem-parts/toyota-oil-cooler-1571050030

it’s actually what the oil filter threads onto.

 

Thank you all for your replies..still coolant is disappearing mysteriously.

I did have the timing belt and water pump done recently.

I read somewhere If there is a leak in this area it would form a crust and not drip anywhere?

 

Cool. Didn't know that.

How is your coolant overflow tank looking? Any signs of overflowing?

 

The tank has done different things.

the first couple of times I noticed that it would be empty.
then one time I filled it to the F line, drove it to the mechanic to have them look at why I’m losing coolant. popped the hood and it was damn near overflowing.
Sometimes I take it for long trips and the coolant level stays the same.
The last time the truck overheated the tank was full yet the radiator was over a gallon short.

 

I hate to say it, but that sounds like every head gasket failure I've ever had.

 

besides the coolant level and overheating due to that, what other symptoms did you have?

 

Those are the symptoms I've had every time I lost an HG (once in a 93 toyota truck, three more times in subarus)

It always started out as a sporadic problem, that got worse over time until overheating happened everytime I drove it.

Weirdly, the times I had a coolant leak from a leaking hose etc...I never had overheating issues, I'd just notice that the overflow was getting empty.

But with a leaking HG, you get high pressure exhaust gas entering your coolant, displacing liquid and pushing it out into your overflow, until you lose it. Then when the engine cools off, it automatically sucks fluid back in from the overflow, and 'fixes' the problem, until you run out of coolant.

Your mechanic should be able to definitely test for this by testing your coolant, for engine exhaust. Its a simple test that will rule out, or confirm a cylinder, to coolant type leak.

 

Might want to pull your spark plugs and see how they look. If you have one that looks super clean, that would indicate that cylinder is being steam cleaned by coolant leaking into it.

 

^^ combustion leak detector isn’t an expensive test. Harbor freight sells them for under $30. Wishing you luck man.

 

This!! ^^^

 

I mean, if the symptom here is lost coolant, combined with strange coolant issues, plus froth in the oil cap, there's still a number of explanations. Froth in the oil cap with no froth in the oil and no discoloration in the oil is suspicious because with half a quart of coolant in the oil, that oil isn't gonna be straight-up black, it will be more like coffee. Lost coolant, there's been some really f'n weird ones on here.

Remember the guy a week or three ago who had a leak in the radiator, but it only showed when he had a friend hold the truck in 3000rpm for more than 20 seconds? There's also leaking that happens often enough there's plenty of pics here, leaks below/next to the throttle body. We've also seen leaks at the front of the engine, like recently with that one member . Furthermore, if the OP didn't burp the coolant properly when re-adding more, it would cause the other symptoms. Also, if there was any work done and OP or someone else didn't clock the jiggle valve on the thermostat between 11 to 1 o'clock.

First thing I'd be doing:

With the engine to operating temp, heater on at full blast, I'd have someone (or a brick/prop) hold RPM at 2000+ and look for leaks, special attention to the radiator and under the truck in general.

I'd also be taking measures to burp the coolant system, just to be sure air is not at play.

Also, I'd be inspecting the back of the block and everywhere else for traces of red/pink crusty dried up runoff from coolant. I'm assuming OP is using the correct color coolant and hasn't mixed colors.

 

This is where you need to start.
Burp the system. Triple check for leaks around the new water pump. Check for hairline cracks on the plastic sections of the radiator.

 

Damn, I missed the bit about the shop doing the water pump. I assume they did the t-stat also? That's fishy as hell. Both because they may not have filled/burped the system and there could be an air bubble causing this, and if they did the t-stat, they may not have clocked/oriented the jiggle valve on the t-stat properly, which would prevent any bubbles from clearing.

I agree with Seth here, priority is to burp the system, again, with the heat on full blast. Whe weird overflow situation is a possible symptom. But man, you really want to find out if they did the t-stat, and if they did, make sure it was installed correctly.

And @woosah just so you know I'm not pulling your damn leg, here's one of about a dozen examples of oil cap froth from people who DID NOT have a head gasket blown, nor anything else weird happening, driving habits, short trip driving, and sometimes climate will cause it:

https://www.tundras.com/threads/coolant-leak-at-water-bypass-thermostat.100216/

 

I did not have them do the thermostat. However they said they “topped off” the coolant(I was under the impression that you had to drain the system to do this job?) with 2 gallons(I think the system calls for 3 gallons and some).

 

Have you guys ever seen someone so happy to have a blown radiator?

It rained this morning while I was driving so I do have to make sure that’s not rain water splashing off the fender. I just went for a long drive so if it was water it should’ve dried off. I parked the car in the garage to pressure check the cooling system is when I noticed it.
The hood was bone dry so I’m assuming the radiator should’ve dried off before the hood.
I do see a slow leak on the pressure gauge with the car off.

Anyways I sprayed the whole rad off and I am going to fill/burp the system and use the combustion gas detector.

 

No, but I'd had the joy of telling someone "I told you so" plenty of times on here.

 

PS - Get a Denso replacement and buy it from RockAuto, 100% success of no damage when bought there for forum members. This is one item you don't want to need to return, and Denso will fit - but make sure you get the one that matches your cab type, radiators are different between the different cabs.

PPS - Also, Zerex 'Asian Red' coolant on the replacement, unless your coolant is not currently red, as it should be.

 

Rock Auto also sells Aisin coolant which is what I use. OEM supplier of Toyota parts so I have to think their coolant is legit.

 

Combustion test is clean. ran full heat blasting hot. I Let it get to operating temp. Revved it up real good. And pumped the doohickey. No change in color. Did it on a low radiator then filled and burped it then tested at the reservoir. Tested at the exhaust to make sure the free oreilly tester works. Btw if anyone ever needs to do this, they let me ‘rent the fluid’…lol

The OEM radiator is even cheaper nearby and saves me shipping and time. I thought about getting the KOYORAD from rock auto but also the shipping issue.

I may order the Alison coolant from them if I can’t get it nearby. I can run straight water for a few days to do a flush, correct?

 

In theory, you could use tap water for a few days, but if you've ever left a glass of tap water in a room for a day or two and drank it, you know how bad that can taste. Think about it in your engine. Granted, the heat will purify it. But still. I'd at least go get distilled water.

 

does anybody know what Toyota calls these or have the part numbers/a diagram?

the pictures are taken from above the radiator/camera pointed at the ground, so these mounts shown are at the bottom of the radiator

i think those may come with the new radiator but not sure.

 

Since you have a DC and IF that is from the front, I'm fairly certain you're actually looking at brackets for the AC condenser.

Are you speaking of the bracket from one of your pictures highlighted in red ?






If it's indeed the Condenser, this is a link for right hand bracket, even tho their dis-continued.
2004-2006 Toyota Tundra Condenser Lower Bracket 88688-0C190 | Toyota Parts (mcgeorgetoyota.com)

Left bracket is 88688-0C200

 

yeah whoops that is the condenser mistook it for the radiator

dang now im hoping those wet spots arent an ac leak but the thing is blowing pretty cold

 

That’s not hard to do given the close proximity but yes, it is your AC condenser and NOT your radiator.

In fact if you look on the sides, you can see a slight space between the condenser and radiator. Noticed when I looked at mine, that I need to add removing radiator to my things to do list, considering the bug blockage and what not I could see on the coil fins.

 

Jeebus, I see what you're saying now. Orientation of the pic being 90 out made me thing it was where the endcap met the coils/fins.

I'll admit, I prolly sat here for a good 5 minutes scrolling back and forth looking at pics, scratching me head, wondering, "are we speaking the same f'n language here?"