hesh LAW

So about a week ago i looked under my hood and saw that my coolant was brown. First thing i thought was a blown head gasket or a cracked head. I flushed the hole system and a week later its starting to brown up again. I only recall seeing white smoke coming out of my exhast twice a while ago. Its not ever over heating, it runs decent so now im wondering if its my radiator or a blown head. The oil looks fine and cant notice any water.
I guess what i need to know is how can i tell if its my head gasket or my radiator rusting up.

92mallcrawler

You can have a test done at most shops to see if there is carbon monoxide showing up in the coolant, which would be a blown head gasket or a cracked head.

5-90

If it's from the overflow tank, dismount and clean the tank. A lot of crud collects in there, and it's not a reliable indicator of cooling system health.

If it's in the radiator, dip your finger in and smell. If you smell oil, it's emulsified oil. If you smell gasoline, you may have a head gasket leak. If you smell neither - and it smells more like wet rusty metal, do a flush and refill (somthing like he two-part powdered flush works well here, with an extra clear-water flush done after the neutraliser.)

I'm almost willing to bet it's rust (if it's in the radiator,) which is a side effect of not changing coolant regularly. If it's in the overflow tank, clean and re-examine in a few days.

(In all honesty, the overflow tank on "open" systems should be washed out each time the coolant is changed, as the crud buildup in there can cause you to mistakenly think you have cooling system trouble, when you do not.)

EDIT - yes, there are some truly wifty diagnostic tools out there. Don't neglect the ones you already own - five senses and a functional brain. You can learn a lot just from using those, you already own them free and clear, and it doesn't cost anything to use them!

hesh LAW

Oh okay, thanks. I cant smell oil or gas, i flushed it a while but will do it again. As for the overflow tank this is where i really have only noticed the brown coolint but i didnt take a good look at the color in the radiator (0nly smelled it). Ill probably take it into a shop just to be certain if my coolint continues to discolor.

But i clean the overflow tank first, never would have thought of that.

tjwalker

What is the history of routine cooling system maintenance on this vehicle?

Not unusual to have to perform multiple coolant flushes if the system hasn't had fresh coolant once in a while.

For ones that are looking tough, I recommend using a coolant flush additive, available at any parts store. Follow the instructions on the bottle!

And yes, thoroughly clean the reservoir too.

fishtaconc

Another option to tjwalker's, drain the coolant, replace with 50/50 mix of vinegar/water, and run engine for 45mins-1hr after operating temp is reached. The flushes work well, but if you have to do multiple flushes vinegar method is a little more budget friendly. A new thermostat from jeep is recommended, and a very good inspection of the hoses,etc. Warm weather is approaching, nows a good time to get ahead of the curve. Is there a oily sheen to the coolant? If you have an automatic, the tranny cooler may be leaking into the radiator, just a thought.

Passt

I recently had my coolant flushed. I acquired my 2000 XJ from a used dealer and had no knowledge of the care the previous owner took. I did all my fluids, and my coolant was in the same state as yours, just a lot of rust. I'm willing to bet that's all it is, based on your diagnostics. Let us know what you end up finding out!

JAYSSICKXJ

X2... Rust..

xjpettit99

Has there ever been any other color of coolant than green put in it? One thing that I find common is people will put red in is which is for most ford vehicles and when the red mixes with the green and heat up they turn a reddish brown and with excessive exposure to temperature creates a sludge. check the color in the radiator to make sure it us just dirt.

AdamG8GXP

I know Jeep thermostat has a small hole in it. The replacement I bought doesn't but it the same, 195°F, as stock. It has been running good for last 6 months. Will this cause anything?

5-90

The hole is there as an air bleed, it's preferred to have it.

I usually drill two 1/16" holes in the flange, 180* apart, before I install a new unit. One hole goes at 12:00, the other at 6:00. The upper hole will pass air out of the head, the lower hole will pass water into the head to displace the air.

Makes the system self-purging of air, and helps keep air pockets (reactor men would know them as "steam voids") from forming behind the thermostat. An air pocket will prevent thermostat function, and usually results in overheating...

hesh LAW

Last sping i changed my water pump and flushed the system, ive only owned it about a year so i cant really say how well it was kept up before.
Started snowing today so im gonna have to wait to flush it again but ill let yall know how it goes.
Thanks for all the advice.

bigbadon

If this is the result of mixing incompatible antifreeze it is impossible to clean the system with conventional flushes. I have had great success using Cascade dish-washing detergent....1/4 cup,run engine for 30 minutes,flush and rinse then rinse again. I never tried this on a Jeep but don't see why it would be any different.

jamurrin

Why wouldn't an ordinary flush work? I'd be a little nervous of Cascade making suds/bubbles and sticking the Thermostat closed.

My old S-10 had a Dexcool/conventional antifreeze mix in it. The sludge plugged the heater core, and lord knows what it did to the radiator. I drained it, flushed the heater core, and filled it with straight water. Drove the car to work the next day, then drained the water/sludge mixture and refilled with clean water. Repeated the drain/fill every day for about two weeks. It seemed to work great. I'd not recommend when temperatures get close to freezing, but that method seemed to work great for me!

bigbadon

That Dexcool will turn into mud when exposed to air and is very corrosive. Cascade will remove it and it does not make suds. I tried flushes and lots and lots of plain water on a Blazer to no avail then done the cascade out of desperation. Not only did it unclog my heater core and radiator but when I looked into the radiator the brass looked shiny and new.