Oil in coolant? Deathcool sludge?

[NMBurb02]

While driving to the airport on Monday in 110F+ heat, the Grand Prix's cooling system wasn't working too well. My ODBII scanner told me the coolant was sitting at about 212F while cruising at a steady 65 mph. I got back last night and checked the radiator this evening to find:

I don't know what I'm looking at but assume it is either oil in the coolant or Dexcool sludge (although I thought the gasket issues leading to sludge were worked out by the 2006 model year). I did a full distilled water flush when I replaced the coolant elbows and thermostat (Stant SuperStat) 2 years/23k miles ago and only used Prestone Dexcool and distilled water for the refill. No additives, cooling system tabs, etc.

What is the likely culprit here and what should I do next? Take it to a shop to have the cooling system pressure tested? Do another coolant flush? I was already planning on doing a drain and fill while replacing the thermostat with an ACDelco unit and putting in some ACDelco cooling system tabs since I have heard that using the tabs is recommended even if there are not any issues.

I am starting a new job in a week and will have to make the 900 mile round trip twice in the span of two weeks until I can move my family out and do not want to get stranded in the middle of the desert with an overheated engine.

 

[69GTX]

Are there any sources of oil that use the coolant system for cooling? (ie power steering coolers, trans cooler, etc.). That's the kind of sludge I'm used to seeing when the power steering cooler fails on the 1998-2002 F bodies and forms mud. If it's not from oil contamination (head gasket?) then it could be from an air leak/low level over time. I'd suspect oil contamination though.

Run the car on distilled water/water wetter for now and find the source of the leak/contamination.

 

[NMBurb02]

The radiator is a shared for engine coolant and transmission fluid. Could this be transmission fluid getting into the coolant via a leak in the radiator?

 

[69GTX]

Very possible. On my 2002, I found a small trans cooler leak into the coolant system early last year. It showed up as small oil dots and blobs at the top of the coolant reservoir. The blobs had a reddish/deep brown tint to them rather than black (ie ATF vs. engine oil). I ended up replacing the radiator. Possibly a cheaper fix might have been installing a stand alone finned cooler and plugging the radiator.

 

[Lyman]

Might want to check your trans fluid.

 

[JimPghPA]

Check the trany fluid and the engine oil for coolant.

 

[NMBurb02]

Originally Posted By: Blkstanger
Might want to check your trans fluid.

The transmission fluid is nice and pink. The sludge is brown and smells only like coolant. Oil looks and smells normal.

Looking less likely to be a tranny fluid/coolant mix.

 

[sleddriver]

The sled's radiator also contains oil + ATF coolers. I use Dex-cool. Was planning to go out of town the next day when I discovered a brown chocolate milkshake in the coolant reservoir. Oil pressure is higher than coolant pressure.

So I spent the weekend installing a new radiator & flushing out the junk with SHOUT.

That looks like sludge to me...but in only two years?? Very odd.

Whatever it is, a simple D&F isn't going to cut it. You need a thorough flush, then an aluminum safe detergent, then a rinse & repeat until your comfortable it's all gone.

 

[Chris142]

That's rusty Dex sludge. That did not happen over night.when did you last take off the cap and look.

 

[Gasbuggy]

Originally Posted By: Chris142
That's rusty Dex sludge. That did not happen over night.when did you last take off the cap and look.



I've seen that in neglected systems. DexCool is 5 year coolant and it looks like someone went 10.

 

[NMBurb02]

Originally Posted By: Gasbuggy
Originally Posted By: Chris142
That's rusty Dex sludge. That did not happen over night.when did you last take off the cap and look.



I've seen that in neglected systems. DexCool is 5 year coolant and it looks like someone went 10.

Chris, I'm not sure the last time I took a good look. I have noticed very minimal film on the walls of the filler neck before but nothing like this.

Like I said, I did a full distilled water flush 2 years ago, so this is not 10 year old fluid. I bought the car 3 1/2 years/40k miles ago and did not do anything with the coolant because Carfax showed a coolant change within the previous 20k or so miles. The flush I performed was because I was draining the coolant anyway to replace leaking coolant elbows. I ran several gallons of distilled water through the system, draining and filling with full temp warmups between until it ran clear, then added the appropriate amount of Dexcool concentrate to get a 50/50 coolant/water mix.

The coolant did run low before the elbows were replaced, so could there have been some rust/corrosion that the water flush did not clean out? Should I try another distilled water flush and use an additive to get a good cleaning before refilling?

 

[JHZR2]

I've never had Dex sludge. But, there are tablets of sealant that are sometimes used... That get a sludge looking later at the cap.

Dex is sensitive to air, so you may have just not topped it up fully.

 

[69GTX]

If your flush before wasn't thorough enough, it's possible some old coolant was left behind that wasn't compatible with Dex Cool. That sometimes causes sludge as DexCool doesn't play well with some other coolants.

 

[NMBurb02]

Originally Posted By: JHZR2
I've never had Dex sludge. But, there are tablets of sealant that are sometimes used... That get a sludge looking later at the cap.

Dex is sensitive to air, so you may have just not topped it up fully.

I didn't use the tabs after I did the flush so that isn't it.

I might not have burped the system adequately and had some air in there.

 

[Colt45ws]

Rust scale from air in the system.
I wouldn't put the tabs in at this time.
Flush it, and replace the pressure cap.

 

[doublebase]

Good old Dexcool sludge...seen it a million times. Yours doesn't look all that bad actually - for Dexcool anyway - maybe another flush would help, but the problem is that your radiator and heater core may be stuffed up a bit. Seen that a million times too.

 

[NMBurb02]

Okay, I will do a thorough flush this weekend and keep a close eye on it. Are the radiator flush additives safe? I can get the Bar's Leak Radiator 10 Minute Flush and Prestone Radiator Flush + Cleaner locally. Is one any better than the other?

 

[BigD1]

Looks like Dexcool sludge to me. A 1998 Malibu that I bought new looked just like that.

Instead of the GM tabs that I have used and recommend, you can also buy a bottle of the Subaru Coolant Conditioner from your local Subaru parts department. The bottle I bought was right at $2.00 plus tax. The Subaru stuff is actually Holts Radweld that is made in England. Sealed up a radiator weep on my Oldsmobile in about twenty minutes. The Subaru stuff is already premixed, so just shake it good, and pour it in. You only need one bottle.

 

[mehullica]

Dexcool sludge/electrolysis/hose deterioration.

 

[Boss302fan]

Dexcool is fine, you just need to check it and do drain and fills... Main issue were gaskets and people not checking and maintaining their coolant system.