Last week my son was driving my 98 EB, 4WD, 4.0 SOHC, 85 k mile Explorer. Check guage light flickered a bit, then came on for good. He checked the Temp guage and it was at the red. He checked the radiator, no coolant in the reservoir and none visible in the radiator. He refilled both and drove about two miles home.

When I checked it the next day, I discovered the radiator was leaking around the metal core/ plastic tank seam. New radiator and thermostat and it now seems fine.

I've always done a 3 yr/36000 mile coolant flush. This seems premature for a radiator failure--is this average for a radiator?

The Explorer seems to run fine, no apparent water in the oil, no white smoke, temp seems normal. Is it likely that no permanent damage was done by the over-temp? Is the 4.0 SOHC particularly vulnerable to overheating?

 

I have 120,000 miles on my 94 and am on my 3rd rad, mostly due to the fact that the 2nd rad wasn't the best, otherwise I'm sure I'd still be on my 2nd. The metal to plastic isn't the best design so I think you got just about what you should get out of your original rad.

Can't say for sure if any damage was done to yours. Keep an eye on the anti-freeze level. Hopefully the heads didn't warp, but by the sounds of it you should be OK. Good thing your son knew better not to drive any further until he refilled it.

 

Look at your manual.... check the coolant capacity. If there are no engine block drain plugs, it's not possible to drain the system completely. This makes flushing with chemicals difficult. You may think you flushed all the chemicals out, but some still remain to cause damage to the radiator core. Since you may not know how much water flush is left in the system after the drain, it also makes it difficult to figure out the proper water to antifreeze mix.

My preference is to only drain and fill with new coolant and do this more frequently than is recommended. I do and drain and fill twice on my Explorer every two years.

When I drain my 2002 XLT at the radiator drain valve, I only get 9 quarts of the 16 quart capacity. So I only replace 56% of the coolant and have 7 quarts of the old coolant mixed with the new. By doing two drains and fills, I get 75% changed, with still 4 quarts of old coolant mixed with the new.

This may not seem like ideal, but it does remove some of the trace suspended engine block rust that would plate out on the aluminum radiator core ( and that's the only reason to replace the antifreeze, as the water, glycol, and additive chemicals don't degrade). I fill with 50-50 mix of green antifreeze and distilled water.

 

Were you able to examine the failed radiator? Was the failure due to corrosion or was it just that the bond failed?

If it was galvanic corrosion, check your grounds. Engine to chassis. Firewall to engine. If there is any doubt, remove them and clean the mating surfaces, coat with grease or silicone grease and tighten then down well.

How long has the radiator been installed? At two weeks or more, use a digital voltmeter on the lowest voltage scale and take a reading between the battery ground and the coolant in the radiator. Do this with all systems turned off, including underhood light etc. Ideally it should be zero. If it is .01volts or more there is an electrical problem. (That is a low number but since the radiator and the coolant are new it should be zero. Over time, there will be a reading of some sort.) If your reading is zero, have a helper open the door and start the engine while you watch your meter. Note any change in the reading as systems are operated. Then have the helper operate all the various systems in the vehicle watching for variations each time. You are looking for any system that has a poor ground that causes a stray voltage through your cooling system.

Stray currents cause galvanic corrosion leading to premature radiator and heater core failures.