[2001 V70 2.4T] Occasional coolant reservoir boilover

[prwood]

The coolant might be coming from the radiator, check the plastic drain plug. I'd try touching it to see if its wet.

@jonesg, I found where the coolant was coming from. It looks like there are some cracks in the PCV coolant hose, just before where the hard line connects to the engine. Location indicated here:

IMG_9832.PNG (164.13 KiB) Viewed 1153 times

The cracks are on the underside of the hose, and the coolant is dripping down from there onto the transmission and then dripping off of that. I watched it for a while from underneath the car while the engine was idling. Initially I would say it was a steady drip (not a stream, flow, or gush), and then while I was watching it, it slowed down and eventually stopped. It didn't appear to affect the coolant level in the reservoir. So I don't know if the coolant just isn't always running through this hose, or if it varies depending on the engine conditions. Not sure how urgent it is to fix this leak since it doesn't appear to be the major cause of my coolant loss.

[abscate]

It’s a low flow part of the cooling system that keeps the PCV system warm , and this helps stop pcv clogging from condensing oil and water in the tube that runs along side. It can wait until spring to fix especially if it’s just a drip, just keep an eye on the coolant level of course.

I’ll measure it on a spare I have , you can replace just the coolant hose part with good quality hose and clamps rather than having to buy the $200 PCV MANIFOLD from Volvo ( and no where else)

Here’s all the functions of that pipe system

[prwood]

It’s a low flow part of the cooling system that keeps the PCV system warm , and this helps stop pcv clogging from condensing oil and water in the tube that runs along side. It can wait until spring to fix especially if it’s just a drip, just keep an eye on the coolant level of course.

I’ll measure it on a spare I have , you can replace just the coolant hose part with good quality hose and clamps rather than having to buy the $200 PCV MANIFOLD from Volvo ( and no where else)

Here’s all the functions of that pipe system

Thanks, that's a helpful diagram. I will keep an eye on the drip, as that's all it seems to be for now. That being said, this leak, and the location of the leak, jogged my memory of past repairs, and now I'm wondering if there's a manufacturing defect in the aftermarket parts I've been installing from IPD. Here's the timeline:

* July 2017: Did original PCV system replacement using kit from IPD which included their aftermarket PCV manifold. Link to kit: https://www.ipdusa.com/products/11110/1 ... ipd-124569
* September 2018: Noticed that the elbow hose mentioned in my previous post had swelled up just before the spot where it enters the block. Contacted IPD since it was just past the 1 year warranty on the part, they agreed to replace the part, so they sent me the PCV breather hose assembly and I replaced it. Link to assembly: https://www.ipdusa.com/products/11258/1 ... 28-9471644
* Here's a photo of the part before I replaced it in 2018:

* January 2021: Noticed coolant leak and found that this same hose on the replacement unit was cracked and coolant was dripping from it.

I definitely don't want to replace the whole thing AGAIN... as we all know, it's a pain in the butt, especially that front manifold banjo bolt. And at this point I'm not sure I'd trust the replacement unit from IPD. BUT, if there's a way for me to replace just that elbow hose without disassembling everything, that would be ideal.

[prwood]

If I have climate control turned off (no AC, no defrost, no heat, no blower), at what point would the engine cooling fan normally kick in? Is there a set ECT temperature threshold where the cooling fan should kick in if none of those other systems are running to trigger it on?

[abscate]

On a P80 about 105C, that’s 221F

[prwood]

So, I spent an extended lunch break today driving around as well as idling, trying to test the cooling fan and possibly trigger a boilover. I was not successful in triggering the boilover, but the cooling fan appeared to work in the following testing configurations:

Configuration A:
- Details: Climate temp set to max, blower set to max, AC set on, windshield defrost mode on.
- Result: Cooling fan activated occasionally, usually shortly after the AC compressor clutch disengaged, but not every time it disengaged. The cooling fan would sometimes run for a short time, but other times it ran for a few minutes. Based on my ECT graphs, it seems that the system was trying to keep the ECT temperature around 185F.

Configuration B:
- Details: Climate temp set to min, blower set to off, AC set off, defrost mode off.
- Result: Cooling fan activated at 221F, and ran until ECT temp had dropped to ~200F. (At this point my lunch break had run too long, and I did not wait to see if it would cool down further - I reverted to configuration A, and the temperature dropped from 200F to ~185F, then I shut the car off.

Here is my data:

Here's the initial drive where I was in Configuration A:

Initial Drive and Idling in Configuration A

Here's the second drive where I was initially still in Configuration A, then switched to Configuration B after idling for a bit in my driveway. The switch from A to B happened at about 13:04. The temperature rose to around 200 while I was idling, then I did a quick drive around the block at 13:09 to try and coax it higher. It kept increasing while idling, and then I drove in and out of my driveway a couple of times at 13:17 and it eventually hit 221F, at which point I switched back to Configuration A.

Second Drive and Idling in Configuration A, then B

Finally this is detail of the temperature peak at 221F after letting it heat up in Configuration B, and then the descent after switching back to A.

Detail of end of last graph, showing ECT temperature peak at 221F followed by cooldown

I have a few theories as to why cooling seems to be working properly now when it wasn't earlier:

1. I had been refilling the reservoir after boilovers using AutoZone 50-50 prediluted antifreeze, but when that ran out I switched to Prestone 50-50 prediluted. Maybe a better quality resulted in a higher boiling point, meaning the cooling fan now comes on before the coolant actually boils over?

2. When testing a couple of days ago, I noticed that the AC compressor was cycling on and off quite a bit. I had a leftover can of AC recharge as well as a gauge, so I measured the charge level when the compressor was engaged, and found that it was on the low end of the "ok" range (not in the "need to refill" range). I added a few shots of refrigerant thinking maybe the system wasn't coming on as often as it should due to the AC system pressure being low, but I'm honestly not sure if it was low enough to make a difference in my case.

3. The cooling fan motor or control module are "on the fritz" and are therefore working intermittently, resulting in some "bad days" (where I had boilovers recently) as well as "good days" (like my testing today).

The one thing I haven't done yet is test a third configuration, which I'll call Configuration C, which would be: Climate temp set to midpoint, climate control set to full auto. This is the configuration I generally use in practice and is the one under which the boilovers were originally occurring. The reason I haven't tested it yet is that it produces a highly variable set of inputs for the cooling system, over which I don't have direct control or observability, so it wasn't optimal to determine whether the cooling fan was actually working. However, I should test this soon since it's the configuration I normally use.

[jonesg]

it seems when the split hose leaks , the system temp rises due to loss of pressure,
then the tank vents through the pressure cap. All because of a crappy little hose.

[prwood]

It’s a low flow part of the cooling system that keeps the PCV system warm , and this helps stop pcv clogging from condensing oil and water in the tube that runs along side. It can wait until spring to fix especially if it’s just a drip, just keep an eye on the coolant level of course.

I’ll measure it on a spare I have , you can replace just the coolant hose part with good quality hose and clamps rather than having to buy the $200 PCV MANIFOLD from Volvo ( and no where else)

Any idea what the internal/external diameter of this hose is?

[prwood]

Today's adventure: driving and idling in Configuration C (Climate temp set to midpoint of 72F, climate control set to full auto, no manual AC, blower, or defrost overrides). Things actually seemed to go pretty well for the first 50 minutes or so:

ECT warmed up during the initial drive to about 195 and hovered around there until I parked and idled at 11:51. At that point ECT climbed to 205 and hovered between 205-210. The cooling fan kicked in occasionally during this time. Then I started driving again just after 12:16, and the ECT plunged during my initial long stretch, then started climbing gradually as I hit a few stoplights. As I was making my final approach, the ECT began a final steady climb from ~195. As I parked at home it passed 202 and continued to climb. It didn't show any signs of equalizing around 205-210 as it did when I was parked earlier, but rather it continued to climb all the way up to 225. This time, there was no sign of the cooling fan coming on at 221, so rather than wait, I went ahead and switched back to Configuration A to try and bring the temperature down. That brought it down to 200, but at that point I was also seeing smoke from under the hood and noticed coolant pooling on the ground under the PCV elbow again. The temperature started climbing again, and then I got the 'coolant level lo' message, so I shut off the engine.

I checked the coolant reservoir and it was completely empty - however, I did not see any signs of fluid around the cap (no liquid and no white residue), so the coolant must have been dumped from some other part of the system - maybe it all evaporated/sprayed from the cracked PCV hose? There must have been a lot that evaporated, because the puddling definitely didn't look like a whole reservoir's worth of coolant. Now I am wondering if putting on a newer reservoir cap and tightening it down more has pushed the coolant system pressure to the next weak point, the PCV elbow.

[abscate]

If you aren’t keeping pressure in your cooling system the BP of the glycol water mix will be about 220F, so that might be the answer here. With pressure, temps up to 260F will be ok.

Sounds like you need to deal with that small pcv hose. I just got home from travel last night. Will measure this morning