[2001 V70 2.4T] Coolant Wars: The Coolant Strikes Back

[abscate]

OKay - I idled the P80 in the driveway and it took 15 minutes to get to coolant temp 87C
Ambient about 24C

At coolant temperature of 85C, the upper radiator hose started climbing from 30C to 75C over about 60 seconds.

[prwood]

A few updates:

1. I replaced the upper radiator hose and clamps with new Genuine Volvo Parts.
2. I attempted to replace the thermostat, but the Torx bolts on top of the thermostat housing (T40 if I recall correctly) are stripped and I could not loosen them.
3. Initial tests idling in the driveway were good - the coolant system held coolant, nothing was leaking.
4. During test drives, ECT behavior was the following:
- ECT initially climbed to 200F (93C) within 15 minutes.
- After 15 minutes, ECT behavior depended on driving conditions:
-- at speeds 30mph (48kph) and below (including idling), ECT went up to 225F (107C), and then settled into a cycle of cooling and heating. It seems that the cooling fan reliably kicked in between 221-227F (105-108C), and ran until the ECT came down to 210F (98.8C).
-- at speeds above 30mph (48kph), ECT stayed between 195-200F (90-93C) and the cooling fan didn't come on, assumedly due the natural air currents passing through the radiator from the vehicle's motion.
5. I didn't see any coolant loss while the engine was running.
6. The place where it appears coolant is still being lost is after the engine is shut off. The behavior depends on ECT at the point when the engine is shut off. If ECT is in the range of 205-225F (96-107F) when the engine is shut off, there will usually be a coolant boilover within a few minutes of the engine shutting off. If ECT is lower than that when the engine is shut off, it seems that the coolant cools down on its own and does not boil over. I was under the impression that the cooling fan is supposed to stay on after the engine shuts off to help lower the coolant temperature, but it's definitely not doing that. I know that I have had a persistent low voltage issue (OBD reported voltage is between 11.7-12.5 while the engine is on), so I'm wondering if the available voltage when the engine is off is not high enough to allow the cooling fan to continue running.

Let me know if anyone has any thoughts on the above.

[jonesg]

voltmeter on the terminals of battery at idle is 14.3v .... on mine.
You might want to check it , then check again at the power box under the hood for voltage drop.

or give it a hot run and put a charger or jumpers on it as soon as you turn it off, see if that kick starts the fan.

Impact hammer for stuck machine screws works for most people, I use an air impact hammer with a "shake n break" .

[abscate]

That low battery voltage will mess up your fan ECU ECT operation so get that fixed first. That circuit is sensitive to voltage for some reason , voltage regulator in the ECU logic circuit perhaps?

[jonesg]

volt regulator on the alternator looks easier to diagnose even if a pain to swap.
If the serpentine belt fails the charge light comes on but if the signal wire at the regulator is corroded the warning light doesn't come on.
Unplug the small blade connector to see if theres green corrosion in the plug. ..mine was bad, the plug fell off the wire.

[prwood]

Unfortunately I've discovered a new coolant leak. This time, as best I can tell, it's coming from the PCV banjo bolt on the underside of the intake manifold, just above the alternator. As you all know, that bolt is a PITA to access. I've done it several times due to having replaced my PCV system several times, but I don't relish doing it again. I'm not sure if there's a way to fix the issue without taking several major components apart. I'm also not sure where it could be leaking from - from what I recall, the bolt goes through the PCV elbow with a copper crush washer on either side, so I guess the washers could be leaking? If I got a wrench in there somehow and cranked down the bolt a bit harder maybe it would stop?

Even so, who knows where the next leak would pop up? I'm trying to think of other weak points in the system. There's another banjo bolt on the other end of the PCV system below the exhaust camshaft. The only other fittings I'm aware of that I haven't replaced recently are the big coolant hoses that go between the reservoir and radiator and the engine block.

There's still a part of me that wonders if the pressure in the system is higher than it should be, and if so, what could cause it?

Luckily I don't have to drive the car for the next few days, so I have some time to ponder what to do next.

[jonesg]

maybe get a endoscope camera for your phone.
https://www.amazon.com/Endoscope-Inspec ... 183&sr=8-5

copper washers should be replaced or annealed every time.

[prwood]

Is there any way to measure the pressure in an actively running cooling system? I know you can get a pressure testing kit that pumps static air pressure into the system to test whether it will hold at a given pressure level, and I had used one several years ago to find some. What I'm looking for on the other hand is a gauge that would measure the pressure while running.

I'm concerned that even if I keep replacing leaking parts, there may still be some underlying issue causing the pressure to be higher than spec.

[jonesg]

a sacrificial coolant cap , drill a hole to accept a tire valve stem.
I think you'll find if its not venting at the cap its not over pressurized, its just weak links cropping up.

https://www.amazon.com/Milton-S-413-Tub ... yAQAvD_BwE

[abscate]

You could run a hose off the petcock on the water pipe to a gauge