Hello all,

When I got home today after driving around town doing some errands, water was coming out of the overflow above the radiator, out from under the cap. I ran the engine, put some more water in it until the overflow was full again, and it never overheated. Temp gauge shows about 1/3 of the way up. Heaters blow warm air. But, when I squeeze the top radiator hose, it is quite hot but there is no pressure. Could it be a stuck close thermostat? Any ideas?

Thanks,
Michael

 

Stuck tstat would be my first guess, having just gone through this whole mess the last few weeks. The top hose should be pretty firm and pretty easy to tell if coolant is properly flowing through as expected. Maybe stick a bucket under the Ex and pop the tstat out and see how it feels in comparison. A motorcraft tstat and o-ring should only run you about $13 from RockAuto, I believe. In my case, my issue appears to have been more a dirty/bad radiator. I ended up replacing the radiator, hoses, fan clutch, tstat, and water pump all in one go since I've got an Ex that was clearly abused/neglected by the previous owners and lord knows what else is about ready to go on her.

If you want to aid your investigations and future monitoring efforts, pick up a Bluetooth OBD2 port adapter and the Torque Pro app so you can monitor coolant temps alongside the engine temps. Much easier to be able to watch coolant temps fluctuate as expected and you know right away when something funny is going on.

 

If it was hot but had no pressure then I'd say your cap is bad. One of its functions is to maintain system pressure to raise the boiling point of the coolant. Are you running a 50/50 mix of coolant and water?

 

I just pulled the t star and boiled it. Opens and closes as it should. Always amazes me how small the opening is in a T stat compare to the diameter of the radiator hoses.

Anyway, I flushed the radiator with fresh water and refilled with water and Mac's rad flush. Drove it for about 10 minutes, got up about half way on the temp gauge and am now idling in my driveway with front and back heaters on. Heaters are blowing hot, nothing coming out of the overflow yet, all looks good. No clue yet what happened. I will idle it for another 10 min or so, then flush it out again and refill with 50/50. I don't think the PO was running a good 50/50- the T Stat was covered with a hard shell of surface rust or something, same as the inside of the overflow. Not sludgy like oil, just a hard shell that cracks off, basically.

-Michael

 

Ok, I pulled the T Stat to do the final fresh water flush, since the water wasn't going to get hot enough to open it. Lots of rust bits. V10 thermostat after mac's rad flush
so, ran the truck with the heaters on full until the hot air was barely warm and the temp gauge almost flat lined. Turned off the engine and let the fresh water run a little longer in the radiator alone and now need to reinstall T Stat and new 50/50 mix. Seems to be working ok, but I am going to order a new Stat to have on hand in the breal down kit. Nobody around me carries Motorcraft so I need to order one.

Anyway, I have to run some more errands in a couple hours, so I'll keep an eye on the coolant level and operating temp. All I can think of is maybe the overflow cap was a little loose or something and I didn't realize it. No clue. With the rad flush in it, I got the engine, sealed, up to temp with nothing coming out of the overlfow, so it's looking like everything is ok.

Thanks,
Michael

 

The problem has returned! I just drove around a bit and when I stopped, the system boiled over out the overflow cap. No problem when driving, but overflow when I stopped. Temp gauge stays at about 1/3- 1/2, , not overheating. Runs ok, but just threw a code- I haven't checked it, but last time it was a misfire. It stumbles a little sometimes, too- I think I need new COPs, but I don't know if that would cause the problem. No oil in water or water in oil, no sign of head gasket issue.

-Michael

 

Go rent a cooling system pressure tester. Pump up the system to the pressure indicated on th cap and see if it holds it. What did the temp gauge indicate when it boiled over?

 

The gauge was showing about 1/3 up when I turned off the engine.

 

I'd spring for a $10 cap at this point.

 

Just ordered a new coolant reservoir cap, thermostat and fuel filter from Amazon. Picked up a set of COPs and plugs from Ebay, just to see if the missing issue is causing too much heat. Will report back in a week when I get it all installed. I wanted motorcar ft COPs, but went with Global. Big price difference and most folks say they work fine.

-Michael

 

I know it's after the fact but if you want Motorcraft COPs for a decent price (they only need to be replaced when proven bad and typically last a very long time) you can get the Denso #673-6000 from RockAuto for around $23-ish each. The cool thing is that these are the actual OEM COPs as Denso is the OEM manufacturer for them and if you peel the Denso sticker off the top of them the MC part number is right there!

 

Good to know, thanks. I figure at least one of the COPs is bad, I wanted to replace all the boots, but that was going to be around $60. I ordered the Global COPs, new with boots, for $48. So, I got new boots and free COPs.

-Michael

 

You can get a set of 10 Denso boots/springs 671-0001 on ebay for $29.95.
Here's an interesting video about Ford coolant reservoir caps -

 

my v10 excursion had same issue at about 175000 mi. There is a thread on here somewhere. Smell coolant in degas bottle. Mine had a very slight ehaust smell. So head gaskets were failing just barely allowing the engine to act as air pump to cooling system. I did my own head gaskets and now have close to 220000 with no troubles.

 

sherman, wouldn't that cause it to blow out while running? This is only happening during heat soak, right after turning off the engine

-Michael