What to Change. The Radiator or the Mechanic?

The Cherokee was acquired on the fly.

I saw it 'parked' at a mechanic workshop and covered in dust. I was told it has persistent and unsolvable overheating issues.

The overheating was so bad the first engine was condemned.

The owner then bought a 'tokunbo' engine and issue still persisted. Owner got furious and abandoned the car.

Now the issue was this, the radiators on early Cherokee Jeeps were the closed system radiators. A closed system radiator doesn't have a radiator cap on the radiator but on the expansion tank. The closed system radiator operates under pressure. Pressure is needed to push the coolant round the system.

[caption id="attachment_122" align="alignnone" width="1200"] Closed System Radiator. Coolant was added only via the bad quality expansion tank[/caption]

[caption id="attachment_126" align="alignnone" width="800"] Open System Radiator...Notice the filler neck on The Radiator[/caption]

The expansion tank was the Achilles heel as it was made from a weak kind of plastic. Over time, it degrades and breaks. This causes a pressure loss and the coolant will simply not flow.

The wonderful mechanics thought they did not connect the hoses well and tried different routings. The routing I met was where the heater core was deleted and its hoses were routed to the coolant expansion tank. So the water pump pushes water through one heater core outlet into the expansion tank and returns through the other into the same water pump....water was not even getting to the radiator!

Apart from this, the car had a leather interior, functional automatic transmission with 4wd, a non functional AC but repairable, good tires plus its a Cherokee with real axles in front and back. It also came with the ever rugged 4.0 litre inline six engine that never dies.

I hit Google and found out the cooling system could be converted to the more simpler 'open system'. I also knew there could be some more 'surprises' but i was ready to take the risk.

I made a very ridiculous offer to buy 'as is'. My offer was too ridiculous I cannot state it here.

The owner was ready to cut his loss and didn't mind selling just to cover cost of the new tokunbo engine. We had a deal.

I have a wonderful guy in ladipo who helps to source parts. I downloaded the open system radiator from Google and sent it via whatsapp to him. I told him to get it for me. He got it within 30 minutes and sent it to me via motorcycle.

I took the new radiator to the mechanics and told them to install it. I also corrected the radiator hose routing. I deleted the heater core completely. Whilst installing, I googled the serpentine belt diagram for that engine and found out the water pump on mine was turning the opposite way. The mechanics had used a shorter belt. I got the OEM belt length online and bought a new belt and directed them on the proper Installation.

We added water and started the car. No overheating. Vehicle was left to idle....no overheating.

Took vehicle for a drive round with 4 mechanics who were so ecstatic and surprised. They had battled with the issue for months. I dropped them off and drive my new Jeep home.

Vehicle had been 'worked' on by very funny rewires. So many wrong connections. The vacuum hoses....gauges not working etc

I have done so many DIYs on this car than I have done in my entire life. So many online resources.

I armed myself with a multi-meter and learnt how to test resistance, voltage etc and adjust to factory spec.

Any 'rewire' who doesn't know how to use a multi-meter is only good at replacing bulbs or relays. How will he for example confirm that the voltage going to the TPS is exactly 5 volts as recommended. How will he confirm that the resistance of the ground is less than 1as required?

This car has been my training mule and I get better daily.

It is my daily driver when I put on my cloak as a Farmer and my training cadaver in my quest to be a better automotive electrician.

Oh...and the vehicle is also a classic too... 1990 Cherokee XJ.....The vehicle that started the real SUV rush