How to unclog engine block for coolant?

I have a 1991 Grand Wagoneer that began running very hot after a recent alternator change. All belts are tight and water pump is workign fine (replaced 6 months ago), and thermostat is new and tested before installation. Mechanic says cause is some kind of clog in the engine block that is preventing coolant form getting to the top of the engine (and therefore never reaches thermistat or circulates past that back into the radiator. Two questions: (1) what can be done to unclog the engine cooling channels (absent pullign engine apart) and (2) is the timing just coinicdental relative tot he alternator change or is there some connection I haven’t imagined. This is my second GW and I also own a '79 International Scott II, so am fairly familiar with the mechanics of non-electronic autos.


I would get a second opinion to be safe. It could be clogged passages in the engine, but it could also be clogged passges in the radiator. You might want to get the radiator flow tested to be sure.

In any case, there are chemical flushes that you can buy at the auto parts stores, but if you use one of these, make sure you follow the directions and get all of the chemical flush out. Your other option is to install a flush and fill kit from an auto parts store and flush the engine with a garden hose. If the problem is the radiator, I would just replace it rather than try a flush.

Installing a flush and fill kit will allow you to routinely flush the system to prevent this from happening again.

I’m with Whitey on this 100%.

Well, perhaps 97%. Flushing every few years with clear hosewater and replacing the fluid with fresh mix is great, but I’m not an advocate of routine chemical flushing.