Dexcool sludge or bad oil cooler?

[07keo02]

Just bought a high mileage o2 that was slightly neglected in the maintenance department. I noticed right away there was green coolant in the reservoir and the cap had a brownish green tinted sludge built up on it. I took it to gm to do a flush but they really didn't do a good job. When I got it back the reservoir fluid was still green but the stuff I drained from the radiator was red, and there was still some junk in the reservoir and sludge on the cap. I am going to do a 3 day flush but is there any way to check for sure if I have An oil cooler issue or if it was a coolant mixture issue? Zero pressure issues after the truck sits I don't think it is head gaskets.

PS: Good to be back in a duramax.

 

[ALLY Fox]

Sounds like a coolant mixture issue. Dex doesn't mix well with some of the older green coolants and will create sludge. If you're not losing coolant, it's probably not an EGR cooler issue. If you heve an EGR cooler you can bypass it if it's leaking or suspect.

 

[07keo02]

Fedaral emmissions truck so no egr. Reservoir is full of this crap.

 

[07keo02]

Getting more concerned. Is this the use of a head gasket sealer or can bad coolant mixture do this???

 

[OregonDMAX]

Dex doesn't mix well with anything at all really except water :roflmao:

You can always check to see if you are getting coolant into the oil or if the oil level is going down. Chances are though it's just nasty green coolant, I would flush it several times with clean water until you get the gunk out and then go with 50/50 dexcool

 

[TheBac]

IMO, yes you have coolant mixture problems. Do as Oregon posted. You've got to flush it all out.

 

[07keo02]

Working on it. I pulled the thermostats and they are ate up. Have to get a new I ring for the crossover pipe it's leaking bad and all flat. Once I pick that up I'm going to flush it however many times it takes. Then fresh coolant.

 

[Ridin'GMC]

Fill it up with water and add the radiator flush additive in and drive for a day or 2. Get it up to temp for a good half hour or more. Then drain it all out and add in the Dexcool. I use CAT ELC with embitterment coolant in mine, it was cheaper for me to get it in a 5 gallon bucket that has a 50/50 premix than the Dexcool premix at Walmart.

 

[c20elephant]

Fill it up with water and add the radiator flush additive in and drive for a day or 2. Get it up to temp for a good half hour or more. Then drain it all out and add in the Dexcool. I use CAT ELC with embitterment coolant in mine, it was cheaper for me to get it in a 5 gallon bucket that has a 50/50 premix than the Dexcool premix at Walmart.

For $14.00 you can buy 100% walk to the other end of the Wallymart and buy a gallon of distilled and have 2 gallons for $15.00...

 

[07keo02]

I bought some 150k prestone yellow/green stuff. Any issues with that since I will have all of the dex gone? Btw, the 2-3 day flush is exactly what I'm doing.

 

[onebaddmaxxx]

Every truck I work on (more so of fords than gms) that i do coolant flushes on, which can be after oil coolers blow, bad coolant, cracked heads etc, I use cascade in the cooling system with tap water. I let the truck idle an hour and let it warm up. Then flush it out. Ill either pull lower hose or open petcock depending on application, and shove the hose in the coolant bottle and let it go wide open. And let it run while its flushing thru. Then ill fill it with cascade again. Go drive the truck for 10 minutes, then flush it all out again, and then fill with correct coolant. The cascade does not bubble, and gets everything out. Oil and everything

 

[07keo02]

Right now I have blue devil coolant flush in there with water and thermostats removed. I'm going to run a few days then flush a couple more times or whatever is necessary. I also picked up a new reservoir, cap, and gm thermostats to put in when it's all done. Hoping for the best.

 

[andy-stevenson]

Also have heard good results using simple green to flush it out.

 

[cwolfley]

definetly the mixture is a problem, also you have a sealing problem some where, more than likely your cap is bad dexcool will grow a fungus (the white crusty stuff you see) when exposed to air..... just a fyi once you get it all flushed and a clean system you can use regular green antifreeze, your service interval would be shorter though.... which ain't a bad thing. i would use green all day long instead on dexcool. just my .02.

 

[Yellow Jacket]

I always replace with Northland Diesel Guard, which is purple and has DCA's in it to protect against cavitation...

 

[TheBac]

Every truck I work on (more so of fords than gms) that i do coolant flushes on, which can be after oil coolers blow, bad coolant, cracked heads etc, I use cascade in the cooling system with tap water. I let the truck idle an hour and let it warm up. Then flush it out. Ill either pull lower hose or open petcock depending on application, and shove the hose in the coolant bottle and let it go wide open. And let it run while its flushing thru. Then ill fill it with cascade again. Go drive the truck for 10 minutes, then flush it all out again, and then fill with correct coolant. The cascade does not bubble, and gets everything out. Oil and everything

Cascade, as in dishwashing Cascade? Does it leave the coolant passages spotless?

 

[Ridin'GMC]

Cascade works wonders. Techs at my work uses them to flush the crap out after testing an engine.

 

[onebaddmaxxx]

Yes tom, that cascade. Works wonders. When oil coolers explode on 7.3s and dt466 its ugly.....just like orbit....squeaky clean lol

 

[Robby Avery]

Subd to the op once you clean the cooling system out and reinstall the thermostats let me know what temp you see after wards my wife's 02 lb7 had a leak on the lower turbo coolant feed line repaired with proper gm hose from work no pressure issues just noticed it seem to run a little on the cold side like 165-170 all day long on warmer days will creep up towards 180 but that's were it stops I wonder if I have a thermostats hung open or if the ect sensor is off the sensor is one I got back in 2009 from Napa wonder if it the culprit thanks in advance

 

[07keo02]

Just an update. After GM's quick flush and 2 multiple day flushes this is what's coming out of my system. I think it is getting better but wow this system was bad. Today, cascade is going in and I'll drive for a few days. I think I'm going to go ahead and test the oil cooler this weekend just in case. Doesn't look like an oil/water mixture though correct?