My 91 7.3 diesel has been overheating slightly while pulling my boat, so I decided to clean the radiator and flush the coolant. I dumped the coolant filled it with straight garden hose water, let it heat up, drove for a while, then dumped the water. Then, I put in a coolant flush and topped it up with water. I ran the engine up to operating temperature then drove around for a while. I dumped this flush and it was kinda gunky. Then I did another flush with water. It wasn’t until after this flush that I noticed the issue. There are chunks of black and blue silicone that were coming up through the cores that are visible under the radiator cap.

I recently had some work done on the pickup, so I called the mechanic and asked him a few questions. He said that the engine looked like the heads had not been pulled in the past five years, so it wouldn’t be a shotty silicone job on the head. He thought that this silicone may have come from a water pump replacement.

When I started the task, I purchased the coolant that was precharged with SCA, and I planned on putting that in the truck. But right now, one day after the flush, it is still sitting with straight water in the cooling system. This leads to my question.

First, should I be concerned with the straight water in the system. Should I be worried about cavitation on the short term that I am working on the radiator?

Second, Can I clean the radiator myself? I have thought about taking the radiator off, taping up the holes, and filling the radiator with CLR? Is this a good idea. Has anyone tried it. I would certainly flush the radiator with baking soda after the CLR soak, as well as flush the engine with water upon re install.

Or would it be best the take the radiator to a shop and have them clean it. I cant find a shop near me that will do it, but my dad is going to check on prices in my hometown too.

Mostly, should I be worried about the water that sits in the cooling system now. And if I can clean the rad myself, what is the best way to do it.

Thanks for the advice.

 

CLR will not rid the radiator of silicone or other man made products ... only organic products and minerals .... short term no cavitation should occur ... but do get it fixed before it begins .... take radiator and have it hot tanked and reamed out to make sure your getting adequate flow ... keep us posted

 

What I ended up doing was taking out the radiator and backflushing it. I did this until I had clean water coming out the bottom (actually the top of the radiator, but it was set upside down). I then duct taped the hose into the radiator and pressured it up several times with my hand, and each time I did this, I held until the cap released pressure, then let my hand go. A bunch of chunks blew out and I noticed the flow out of the opening slowly increased, from about 1/3 of the diameter of the opening to nearly the whole opening.

Once pressuring was no longer producing chunks, I sealed up both openings of the radiator, and poured in two bottles of gunk radiator cleaner, and flipped the radiator around for about a half hour. When I dumped it, i got a dirty green liquid, so I am guessing that a few more plugged cores in the radiator opened up. Another backflush and pressure up produced a bunch more dirty coolant and chunks. I did this until I again had clean water flowing through.

Then I replaced the thermostat with a new one. About 30 bucks from Ford, and the gasket was 12. I then verified that my heating issues were resolved, which they are to an extent, though I still want to get an aluminum radiator some day. It is now sitting with Fleet Charge coolant precharged with SCA additive.

Which reminds me. Does anyone know where I can get SCA test strips. I asked the guy at NAPA, and he had no idea what I was talking about.

 

Some of these radiators cant be rodded out like most. I took the radiator from my 93 in to have it cleaned, but the tubes are spiraled to improve the coolant flow but also prevent a rod from being pushed through to clean them. I'm not sure if all IDI factory units are like that or if it started during a certain model year. It's just something to be prepared to hear if you take your radiator to a shop.