Wondering if you can offer some suggestions or strategies for addressing an engine coolant loss? I have ’91 fox body, 302, stock.

Over the weekend, my WATER gauge suddenly registered a temp of 250 (pegged the highest). Appropriate range is 180-190. It was appropriate within 2 minutes of the sudden spike.

I allowed it to completely cool down. Then completed a 2:09 hr backroads cruise. Throughout trip, temp appropriately registered as 180-190.

On my trip back to LaCrosse, cruised interstate at speeds approximately 80-85 (Wisconsin has HIGHER speed limits J), I noticed that once again, the WATER gauge temp registered 250. I pulled over and let it cool down. I checked the radiator & it needed coolant. Purchased and dumped in almost an entire container.

Back on the road, within 1 hour of driving 80-85 mph, again noticed WATER gauge registering 250. Seems that I was out of coolant again. I pulled over to assess where coolant might be leaking. No visible leak on/around the engine. Only leaking was from the overflow on the radiator recovery unit.

I searched suggestions online. One individual suggested: “The first thought that comes to mind is that the coolant is getting pushed out the reservoir overflow tube when the engine warms up because of a bad radiator cap.” While this sounds suspicious to me, visually that is what I observed at my last stop. Could it be that high temps were reached when driving on Interstate & not backroads. If radiator cap failed, it was not able to relieve pressure, thus pushed it to the recovery unit and out the overflow. ?? What are your thoughts?


My plan is to pressure test radiator cap (I’ve already bought a new one – I’ll replace the rad cap if I can’t determine any other cause). I plan to pressure test the coolant system this evening.
When I parked last Saturday, the oil dipstick did not seem to have any foaming substances within the mixture. I’ll check for that again tonight.

Any other suggestions on what might be going on?

Again, I run a ’91 fox body, 302, stock.

Thank you for any and all suggestions!!
CraigF