oil in the side coolant reservoir (1 Viewer)

[GregMacd]

My mechanic was doing some repairs on my 1995 TLC and he noticed some dirty oil in the bottom of the side coolant reservoir. (I think that this is the part circled in red in the attached photo). He wasn't sure how this occured, or if it means that this is a sign of a bigger problem with the engine. He didn't think there was an issue with the head gasket, because the engine pressure was normal. He said that it almost appears that someone (e.g. an untrained person at an oil changer place that did not whow where you add engine oil) may have accidently poured oil into the side coolant reservoir, but this would't explain why the oil was dirty.

* The TLC has 289,000 miles on it and the engine was never rebuilt. I had the valve cover gasket replaced about 15 years ago, because of oil leaks. However, over the last 20 years, I've been pouring about a quarter of oil in the engine with every tank of gas. I'm assuming that the seals are worn.
* My mechanic recently fixed a leaky power steering reservoir. I had been pouring in a lot of power steering fluid. However, I don't think that excessive power steering fluid would have a way to leak in there, because they are on opposite sides of the engine.
* I had the radiator replaced 2 years after it cracked. Is it possible that oil mixed with the coolant in the old radiator after it cracked, and then it made its way into the side coolant reservoir?
* Any ideas of how this may have occurred?

 

[flintknapper]

Not very likely it would be oil in the 'bottom' of the overflow reservoir. Oil will float on top of water/coolant unless it emulsified in which case you'd probably see oil all over the inside of the reservoir.

The overflow reservoir's job is to accept a certain amount of coolant from the radiator (as the coolant expands from being heated). Then when the engine cools off.....the coolant from the reservoir is drawn back into the radiator (via the vacuum created).

The ONLY path for oil/other containment to enter the reservoir is through the coolant in the radiator....OR someone having put something directly into it.

There are any number of ways that engine oil could be getting into your coolant. Head-gasket failure would be one. A leaky gasket at the engine oil cooler would be another.

Not sure why your mechanic discounted the head gasket simply because you have good cylinder pressures. That would have nothing to do with a H/G failure where you have coolant to oil port blown (water in oil or vice/versa). Head gaskets can fail in a number of ways. If your mechanic does not understand that.....I'd find a new one.

If I were advising you....I'd recommend you clean/replace the reservoir. Make sure your coolant is fresh and at the proper level of fill. Continue to drive the vehicle and inspect the reservoir from time to time for any contaminants.

IF at some point prior a 'sealer' (stop leak) was added to the radiator or engine....that is most likely what was in the bottom of the reservoir. In any case.....it sounds like your vehicle is running well enough....so if not overheating, I wouldn't be too concerned at this point.

 

[77mustard40]

Agree with @flintknapper , I did have a head gasket failure at 238K and "found it" by noticing I was loosing about a half inch of coolant in the reservoir with each fill-up. The truck as running fine but since I had replaced all hoses and had a newish radiator cap I knew something else was up. Leak down test of the cooling system confirmed my suspicion. Wasn't excited to do a head gasket, but hey now I don't burn a drop of oil.

Keep an eye on that reservoir, hopefully it was just dirty.

 

[suzuguru]

I agree with the above, and would add that I would be looking for a new mechanic after hearing what he had to say on the matter.

 

[GregMacd]

Not very likely it would be oil in the 'bottom' of the overflow reservoir. Oil will float on top of water/coolant unless it emulsified in which case you'd probably see oil all over the inside of the reservoir.

The overflow reservoir's job is to accept a certain amount of coolant from the radiator (as the coolant expands from being heated). Then when the engine cools off.....the coolant from the reservoir is drawn back into the radiator (via the vacuum created).

The ONLY path for oil/other containment to enter the reservoir is through the coolant in the radiator....OR someone having put something directly into it.

There are any number of ways that engine oil could be getting into your coolant. Head-gasket failure would be one. A leaky gasket at the engine cooler would be another.

Not sure why your mechanic discounted the head gasket simply because you have good cylinder pressures. That would have nothing to do with a H/G failure where you have coolant to oil port blown (water in oil or vice/versa). Head gaskets can fail in a number of ways. If your mechanic does not understand that.....I'd find a new one.



View attachment 3570172

If I were advising you....I'd recommend you clean/replace the reservoir. Make sure your coolant is fresh and at the proper level of fill. Continue to drive the vehicle and inspect the reservoir from time to time for any contaminants.

IF at some point prior a 'sealer' (stop leak) was added to the radiator or engine....that is most likely what was in the bottom of the reservoir. In any case.....it sounds like your vehicle is running well enough....so if not overheating, I wouldn't be too concerned at this point.

Thanks! Your response is very thorough and informative. I like the theory of the "stop leak" being poured in the reservoir. I saw that barsleak(dot)com states on its website "If direct access to radiator is not available, install in overflow/reservoir tank." Thus, someone (maybe me?) may have poured stop leak in the reservoir. I don't recall doing so, but about a year before I had the radiator replaced, I put a patch on it, so maybe I pored the stopleak in the reservoir

 

[GregMacd]

Agree with @flintknapper , I did have a head gasket failure at 238K and "found it" by noticing I was loosing about a half inch of coolant in the reservoir with each fill-up. The truck as running fine but since I had replaced all hoses and had a newish radiator cap I knew something else was up. Leak down test of the cooling system confirmed my suspicion. Wasn't excited to do a head gasket, but hey now I don't burn a drop of oil.

Keep an eye on that reservoir, hopefully it was just dirty.

How much was it for a new head gasket?

 

[77mustard40]

How much was it for a new head gasket?

I didn’t have the time to do it myself so I paid a local Toyota / Lexus specialty shop $3500 in labor and purchased the parts myself. I took the intake home and was able to replace all the vac lines myself. I also hit the deck for a fuel filter and insulated the wiring harness above the EGR before it went back together, all in I’d say close to $4,300. All cylinders looked great with original cross hatching still evident, and the truck has been perfect since that was done. I’m at 249K now and all is good.

 

[Timpanogos Slim]

I bought the below kit to verify my suspicions of a head gasket leak.

Get the engine to normal operating temperature, shut down, take off the radiator cap, install the stopper and airlock, put a little of the test fluid in the airlock, turn engine back on.

If the liquid changes color within a few minutes, there are exhaust gasses in the cooling system.

By the time i brought my rig home it was over $6k, but there was an awful lot of "while you're in there", the timing guides failed, engine had to come out to pull the timing cover and replace timing components, etc. And i did none of the labor because i have no garage.

Runs GREAT now, gets much better freeway mpg too.

https://www.amazon.com/gp/product/B07RS3N98V/

 

[Shipwreck]

In addition to the excellent advice above, I can suggest also:
1. Send an oil sample to Blackstone for analysis. It can determine if coolant is moving into your oil. This can be evidence of head gasket or oil cooler leak.
2. A brown sludge can be observed in the bottom of the overflow reservoir if green glycol based coolant is mixed with the silicate/phosphate free Toyota red coolant. The silicates in the green coolant will drop out of solution leaving deposits in the cooling system. Perhaps that is what your mechanic is seeing.

 

[80t0ylc]

There are any number of ways that engine oil could be getting into your coolant. Head-gasket failure would be one. A leaky gasket at the engine cooler would be another.

Could you explain what you mean by "engine cooler" in the last sentence (highlighted)? Curious to figure out what you're talking about.

 

[CharlieS]

Possibly the oil cooler mounted to the side of the engine? US Passenger side, under the exhaust manifolds.

 

[flintknapper]

Could you explain what you mean by "engine cooler" in the last sentence (highlighted)? Curious to figure out what you're talking about.

Yes, sorry....didn't proof read my post. Should read Engine OIL Cooler.

It is on the passenger side underneath/behind the exhaust manifolds.