I noticed after driving home recently and pulling the jeep into my garage that the radiator fan was running on high and the temp "analog" gauge was a couple of clicks off center. After about a minute of idling the temp quickly normalizes and the fan comes down to a lower speed and all is pretty much copacetic again. I should mention that we do live at the top of a steep road.

This is out of the ordinary though as I've never noticed the fan running that loud before. Since I've been away the past few weeks, I asked my wife about it and she says it's been doing that more and more the past two weeks but only after getting home.

In all other conditions things appear normal...highway driving, town driving, etc.

So I open the hood and check the coolant expansion tank. It's nearly empty. But the thing that alarms me the most is that there is a layer of what I can only describe as sludge on the walls at the bottom of the tank. Da freak is that? I start doing some investigating about this new crap that Chrysler uses for coolant and don't like what I read at all. My jeep is supposed to take this new high mileage stuff called OAT. Who here knows about this crap?

Apparently it's completely incompatible with any other coolants, particularly HOAT. Mixing these two together will cause coagulation and over a short amount of time if not flushed out, will destroy a car's cooling system. Why would Chrysler start using this OAT junk? My fear is that some schmuck at the dealership while servicing my jeep topped up the coolant with possibly HOAT instead of OAT and now I'm starting to see some side effects. But proving this seems all but impossible.

But if not that, what is this sludge? Has anyone experienced anything like this?

Oh and did I mention that this OAT crap is priced similar to liquid platinum?

There's also a great deal of confusion about the color of this stuff (purple) compared to HOAT (orange) and the OAT that Fiat uses (also orange)...yadda yadda yadda...I think you can see where mistakes can get made.

Freakin' jeep. Gotta love it...or not.

A pic of the crud as best as I can get it:

Anything I could offer would be pure speculation as to the cause of the sludge. But what you can do is two things:
1)Check the coolant level of the radiator
2)Pop open the drain valve (using a clean catch container) and drain a little out and inspect it.

In either/both case(s) if it appears the correct color, then it might just be something that made it out of the system. I don't know if you can clean the overflow bottle but you can look into that.

ETA: Make sure the coolant level is appropriate for cold or hot and refill as necessary.

If it's not the right color, get a flush and refill...

You'll never get them to admit they put in the wrong coolant even if it's obvious.

Get thee to thine jeep dealer! Let them figure it out and tell you.

You may be seeing something not related to the coolant. When an engine is turned off, the thing goes into heat soak. That's nice for saying it kind of overheats. When its been working hard, like driving up a steep hill, you would expect the heat soak condition. As long as it cools down fairly fast, its nothing to worry about. A coolant problem is something to get straightened out.

Subaru has the same thing. As soon as the warranty expired I had it replaced with coolant that's cheap, and available anywhere.

quote:

Originally posted by rburg:
Get thee to thine jeep dealer! Let them figure it out and tell you.

I'm there right now as a matter fact. The guy here is telling me it's normal. Coolant breaking down or some nonsense. Fine. Well I just had my name called and picked it up after its service. I popped the hood and looked in the reservoir and of course what do I see? Green coolant was added. Perfect.

I bring the guy over, he takes a look, and says they'll suck it out of the reservoir and put in the right stuff. Man, I'm not happy.

And it was like pulling teeth to get him to write it down on my invoice what they did.

I'm thinking I might just have this thing flushed now just to ease my worried mind.

quote:

But if not that, what is this sludge? Has anyone experienced anything like this?

In a properly sealed, pressurized system, with no plastic components, OAT coolants work fine. But it actually attacks plastic, which is why GM had so much trouble with Dex-Cool and intake gaskets and why your plastic reservoir is discolored. And it doesn't like to be exposed to air. It will form sludge and eventually rust. GM 4.3 engines had a lot of problems with that as well, the causes for another topic. Does it have a cap like this?



The gasket must not be swollen, and the cap must also pump up to and hold whatever the specified pressure is.

If you can be sure of getting all of the old coolant out, there is nothing wrong with replacing it with plain old green ethylene glycol. You just need to change it every couple of years. And if the reservoir is nasty it can be easily replaced.

quote:

Originally posted by egregore:

If you can be sure of getting all of the old coolant out, there is nothing wrong with replacing it with plain old green ethylene glycol. You just need to change it every couple of years. And if the reservoir is nasty it can be easily replaced.

I'm thinking I might just do this.

Mixing different coolants causing "coagulation" is a myth, BTW. What mixing does do is take away the 100,000 mile servicing property. Since it's about time to change it anyway, no harm was done.

Make the dealer service people COMPLETELY flush your cooling system.

On the "German" cars, we do this every two years with distilled water and then add fresh/expensive antifreeze diluted to 50% with distilled water.

Yeah, PITA, but it helps.

Good luck,

RMD

Yep - They put the green in, the get to flush and refill. Don't accept draining the overflow tank.

There's quite a lot of discussion (with pics) over on the jeepgarage dot org forum. You might find some nuggets of info that could help? I hope so. Good luck, man.

quote:

Originally posted by egregore:
Mixing different coolants causing "coagulation" is a myth,

That makes me feel better hearing that from you.

Perhaps I've been reading too much internet lore since yesterday.

There is a group trying to get a class action lawsuit formed up against Chrysler / Jeep. Seems that they may not have flushed all of the sand out of their castings. It is migrating out into the radiator, heater core, and everywhere else that coolant cycles.

Also, some of it is getting into the oiling systems. Apparently Jeep is trying to say it's not an issue.

Yeah they shouldn't have put the green in for sure. I would have it flushed for sure. I run dex cool in my duramax and actually have been very happy with it. If you switch to green make sure it's flushed really well.

Dodge had a recall several years ago for casting sand in Cummins Turbo Diesel engines on their pickups. My sister in law had a truck that got the engine completely torn down and rebuilt by the grease monkey at the Dodge dealership in Monahans. I told her she should get rid of the truck when they returned it to her, because I didn't trust their shop to do as good a job as Cummins could. Their shop conditions didn't exactly inspire confidence.

This bullshit with 6 different non-compatible types of coolant that not even the dealerships can keep straight is ridiculous.