Last two times I've driven my Bronco, it has overflowed a bit when I come to a stop. In both cases, I had run at higher rpm just before coming to the stop. I don't have an overflow bottle. This hasn't happened to me before in the 25 years I've owned this one. What should I be looking at?

BTW, when driving, the temp sits at 190 or so.

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How long were you sitting / stopped before it started overflowing ?

What is temp when you stop / sit ?

Have you replaced the coolant that “left the building” ?

It’s been pretty hot lately and maybe your cooling system has just started to degrade over time. Have you checked some of the fundamentals like proper coolant level, last flush / service, thermostat functioning correctly ?

Btw..........have you considered adding an overflow / recovery tank to recapture the expanded coolant once everything cools back down ?

Yes, replaced the lost coolant. I actually replaced the upper radiator and bypass hoses this morning. Old one had a very soft spot.

Today, it happened when I pulled up to my house and stopped to put in reverse and back in to my driveway. Left fluid on my driveway. I'll have to watch the temp cause I'll be honest, I wasn't at that moment.

I warmed it up after replacing the hoses and the temp dropped when the thermostat opened at 195. Didn't have the issue then but it was just running in my driveway.

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One other observation, if I shut it off and then turn the key to on, the temp gauge goes to 230. Start it and bring it up off idle and it drops back to 190. Shut it off and you can hear the fluid in the hoses. Almost sounds like it's boiling. I'm still using the old green stuff mixed 50/50.

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Seems like your thermostat is working properly.

I would think about flushing the cooling system and putting all new coolant in.

Depending on age of radiator, it may be partially plugged and need to be rodded / hat tanked.

I bet the cap isn't holding pressure.

What Viper said.

Replaced the cap. Took for a 20 minute or so drive. Held at 190 till I was headed up hill towards my house at 50mph. It climbed to about 200. Pulled into the gas station to fill up and puked some. I had put 16oz bottle in for overflow and that ran over. Got it home and the top hose is at 235 degrees. I don't think it's the cap.

Belts are tight. Replaced them a month ago. Rechecked them before heading out.

So, flush system next? Then?

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Ok, so in true Project Downward Spiral style, is this the right time to swap to the Explorer front dress? I have everything, well mostly everything, sitting on the shelf. I'd need the belt and would need to change over from the stock alternator to the 4g. Also, probably need a custom hose for the power steering. What else?

If I'm going to swap the water pump, doing the rest doesn't like that much more work. Or is this still on the list of reasons that I'm ?

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That is what I would do.

But I still suspect your radiator is partially plugged.

for Serp belt...also need an Electric fuel pump and Fuel pump relay

The explorer timing cover has no provision for a mechanical pump.

I’d pause and find the root cause for your overheating before throwing parts at it. If it’s a restriction, then look at flushing the system with an aggressive chemical. If it’s still overheating then I’d suspect the radiator or a head gasket. Pull the plugs, is one or more cleaner than the others? If yes, you can confirm with a test for exhaust in the coolant. All plugs the same, then it’s the rad, and a rebuild isn’t the cheaper route, a lot of parts stores sell a new rad for the price of a rebuild.

Definitely going to start with the radiator. Will pull plugs. My thought was if I had to go to swapping the water pump was it might be better to go to the serp setup since everything is off and I have it sitting here. The fuel pump is additional thing I wasn't aware of. Thought that was on the block for some reason vs the timing cover.

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Guessing, while I have it drained, I should pull the thermostat and check it as well to ensure its opening all the way.

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I know it can be frustrating to lose so much coolant doing these repairs, but you can run straight water. The trade off is, straight water has better heat transfer properties, so you may mask the issue you are having now by using it.

Perhaps if you have put new coolant in, you can drain it into a clean bucket and use some sort of filter (paint?) when you put it back in.

Backflushed the radiator. Ran water through it til it ran clear. Didn't take long. If it's blocked, I'll be surprised. Especially since it had been running well all summer. It's a three core, stock radiator that I had re-cored ~20 years ago. This thing has always run on the cool side. Then one day, it didn't.

I checked the driver side plugs, they all looked the same (and surprisingly good). Need to pull the passenger side to check it as well.

Thermostat is operating as when it warms up it goes to 190-195 then kicks down to 170 and then goes back up. I did run it with straight water today, mainly to flush the system before I run the radiator flush chemicals (per the directons). It didn't take long to boil over after it came up to operating temp.

FYI, this started 2-3 weeks after I swapped the belts. My gut tells me the water pump is the culprit. The downside is that at sometime since the last time I changed the water pump (in the 90's), is that the spot on the timing cover where the top bolt of the water pump goes through broke. It's not leaking right now but my fear is that if I try to swap the water pump that I won't be able to get it to re-seal and will need to change the timing cover. Sigh.

Pulled passenger side plugs. All looked the same. Interesting enough, the passenger side looks to be slightly richer than the drivers side.



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Sounds like it's time for EFI in addition to front dress. But my rig has been down forever, so....

Pretty sure this means "damn it". Going to wash it out and retest just to be sure.

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Is this a decent gasket kit?

https://www.rockauto.com/en/moreinfo.ph ... 79&jsn=976

Really hoping I can get away with just gaskets. If not, there's a good chance my Bronco won't be at Super Cel.

Really hoping I can get away with just gaskets. If not, there's a good chance my Bronco won't be at Super Cel.[/quote]

How was the second test?? I had to google the test kit you got as I've never seen that before. I haven't heard anything bad about Fell Pro gasket kits that's what my builder used. Fingers crossed in hopes the Bronco makes the trip!

Tested the exhaust just to see the color turn. It definitely gets a lot more yellow so assuming it's a head gasket, it is just a "small" leak but obviously enough to cause big issues.

The top radiator hose gets very firm as it reaches temp so something is adding pressure.

If anyone has tips on the gaskets, let me know. Going to tackle it Saturday. I'll follow the Chilton's that I have but I've never done this job before but that won't stop me.

If you want to swing by and help or watch, just ping me. Will probably try to tear it apart on Friday night since that should go faster, right up till a bolt breaks. #downwardspiral

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