1991 Jeep YJ


Randy Pertner

July, 19, 2010 AT 10:26 AM

Engine Cooling problem
1991 Jeep YJ 6 cyl Four Wheel Drive Automatic 50000 miles

My daughter has a 1991 Jeep YJ Wrangler. It is and always has been a California vehicle. We purchased it from the original owner and he used it as a tow vehicle behind his motor home. Since he owned a car dealership the car was maintained excellently. Even though the odometer showed 80,000 at the time of purchase he had documentation that 50,000 of those miles were from being towed. It now has 100,000 miles showing equating to 50,000 miles of actual driving. It has always run great, but lately it has been overheating. We took it into a mechanic who said the water pump was going out, but the bigger issue is he said the engine itself is full of rust. He said he recommends putting the new water pump on it and then selling it immediately because the rust issue is going to lead to further damage with the other components of the engine. Is there a way to deal with this interior engine rust problem? What would cause the engine to do this in the first place? My daughter loves the car and has put a lot of money into getting it just the way she wanted it (Lift kit, tires, rims, etc.) I hope you can offer a solution.


6 Answers



July, 19, 2010 AT 11:30 AM

Hi Randy Pertner,

Thank you for the donation.

When coolant is not used in the cooling system, rust would form. Get the water pump replaced and while the water pump is out, flush the block and radiator with water to clear the rust.

After installation of the water pump, fill the radiator with coolant and the rust problem should be contained.

Coolant is an anti-rust agent.


Randy Pertner

July, 19, 2010 AT 11:54 AM

I was hoping for a little more indepth response than put coolant in the engine once water pump is replaced. I already knew that and the car has always had coolant in it. Is there any other reason it would have this heavy rust issue? Are there other components I should replace while replacing the water pump? What is the best way to fully flush the rust out of the engine when I have the water pump off? Is my mechanic right that my daughter should unload the Jeep and that this is going to be an ongoing issue or is there truly a way that I can stop it and keep it from coming back?



July, 19, 2010 AT 1:11 PM

Coolant comes in different qualities. A good quality coolant would prevent rust from forming whereas a cheap quality would.

If as you said the rust is bad, then you would have to check the water jackets, pipes etc. For corrosion and clogging. Even the radiator has to be checked.

If the cleaning of the system is done well and the correct amount of coolant is used, I don't see how it is going to be an issue.

If you are worried about it, then yes, I would agree that you let it go.



July, 19, 2010 AT 3:32 PM

First off take some coolant out of the engine and see for yourself how bad the rust is. If theres chunks of metal in it, which I doubt it it probably plugged up radiator also and heater core and replacing water pump will not all fix it.

Best way to flush it is just take off the upper hose and just keep running water through it till it cleans up. It takes ALOT to rust through a block belive me. I have yet to see it happen. And most of the rust you do find is from heater core and radiator degrading along with parts from the water pump when they go out. Just flush it out and put coolant in and you really should have nothing to worry about. Even if that didnt stop the rust it would be way past the life of the vehicle before it would rust bad enough to start to really affect things.

After you fill it with new coolant after flushing it or water because I suggest after running it for a bit draining the system again and keep repeating it untill the water is free of rust particles.



July, 19, 2010 AT 3:42 PM

Run a special chemical cleaner to the existing coolant to remove rust, sludges/scales and then reverse flush it and ensure you use the correct type of coolant as specified when flushing is done.



July, 19, 2010 AT 5:47 PM

I would also have the radiator removed and get the core cleaned as if the rust is deep seated, flakes can start to block radiator core tubes and often just a back flush may not be enough to dislodge these particles, a radiator shop will take off the top & bottom tanks and clean the cores of and blockages, you may have a number of blocked tubes and still have some circulation through the others, but not enough to maintain correct temp control.

Mark (mhpautos)

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