Still overheats after passing block test

[party ford se]

What's up everyone. I have 2012 ford fiesta 1.6l non turbo USA. I've done so much work on this car but it still overheats.

I bought the car with the engine overheating and blasting white smoke out of the exhaust. with the coolant bubbling in the reservoir. I have since, replaced the head gasket, coolant outlet gasket, thermostat, water pump and resurfaced the cylinder head with new head bolts. And properly bled the cooling system.

The car still performs the same after all of these repairs. The car still passes the engine block test (same as before the repairs). And there was never signs of coolant in the oil or oil in the coolant (before or after the repairs).

A compression test determined cylinder 3 had 120PSI and all the rest of the cylinders were around 110PSI (I was told by a dealer tech that the normal range was within 100-110PSi). All of the coolant hoses get hot and my heater blows nice warn air. There are no coolant leaks and the system holds pressure at 13 PSI for 10 minutes without falling down. The car idles perfectly.

Why is this engine still overheating? Is it possible to have a cracked cylinder head/engine block even with a passed block test and good compression?

 

[Handy Andy]

Ok, usually this means you have had the block inspected. So if there was any scale, cracks or other blockage, it would have been found and you would have been told about it.

So with all this done yet the head looks "clean" - then let's step back a moment and think about the "Whole" picture.

What I'm asking you to do, is to check the radiator - is it plugged?

Reasoning, your original condition the motor was in, - caused an overheating problem. So by process of elimination - the only other options are external to the motor - if coolant gets to the heater core, that works, but what about the bigger elephant in the room, the radiator? What condition is it in?

 

[party ford se]

Hey. Honestly, I've only done a visual inspection of the engine block myself. I have not had my block inspected professionally. I personally did not see any cracks or damage to it when I removed the cylinder head.

I believe the radiator is in good condition because it visually isn't damaged and when I drained the coolant out from the bottom hose, lots of coolant came out initially, and the stream slowly decreased until it all drained out. Also when the car gets hot, all of the coolant hoses are around the same temperature.

My radiator fan kicks on as well.

If the engine block is bad wouldn't the block tester fail/the engine have a misfire/compression be unusual? (All 3 symptoms don't exist on the engine)

 

[Handy Andy]

The higher pressure on the one cylinder might indicate a sealing issue either by valve or hydro-static lock caused by a leak into the cylinder by coolant forcing itself thru a hole or crack.

But in most cases of the engine with a bad seal - you'd see pressure build in the coolant tank and may even see the coolant tank active from air bubbling up from the block thru the main coolant hose into the container and can be confirmed by slowly twisting off - loosening the coolant container cap - will also deflate in size and change the level of fluid seen - by releasing pressure. This would happen after driving an simple short trip or just letting it idle - after a short time. This is normal, yes, to a point of longer amounts of time, but realize that the air getting pressed into the coolant from that leak can make the tank inflate like a balloon and even burst from the rapid build-up of pressure inside it.

You'd even see. potentially - steady streams of bubbles as the cylinder with that crack formed the compression stroke that forced out the air back into the coolant side of the cylinder sleeve.

So you know the fan works, and the engine gets hot, how is the burp line doing? It may play a role in this if it's plugged or the bell/bubble valve in the line back at the top of the rear exhaust side of the head - if that valve is stuck shut - air pockets can form and stay there from the pressure and there's no coolant that can flow in there to take heat away - only thru the cylinder head aluminum can the heat be dissipated. The bubble valve is where that smaller hose comes from the rear of the engine that if it's not able to drain out or burp air from that "high spot" in the cylinder head - can put the vehicle right back into the shop from it.

To fix that bubble valve it's a small pen-tip side valve that slides in and out of a larger tube in the orifice that this line mounts to - in the cylinder head - it has to be pressed out - or that pen-tip part just simply removed. There's a cost to this - it will take a little longer to warm up the vehicle because there is now a little-less restriction to the circulating fluid that the thermostat is supposed to do the job for you - that was the purpose of that check valve - to keep the air from forming and give it path out, but keep the fluid behind it from flowing out with that air.

 

[scotman]

I would be looking at a different radiator. It could be plugged up. If coolant doesn't pass through the core, it is not shedding heat.