Just need a new coolant cap. Start there.


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Just need a new coolant cap. Start there.

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Already done. Unless the replacement was bad too, that didn't work.

 

I'd put a coolant pressure tester on it and see what happens. How old is the coolant tank? Sometimes they crack and leak only when under pressure, sometimes the metal sleeve in the bottom corrodes and causes a crack and subsequently a leak. Is the bleed line from the radiator to the top of the tank pinched?

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As far as I know, it's the factory one. I have no knowledge of it being replaced, I only got the car last month. For the bleed line, it looked alright, but I'll check again. Thank you for the reply.

 

Check you lines coming off the tank. Also check the short line down by the firewall. Are the hoses coming off the radiator soft? As posted above, how old is the coolant tank? Mine did the same right after I bought it. IIRC the tank and cap were toast as was the short line (could have been my 850), but I replaced ALL hoses along with new tank and cap. No issues since.

 

The top hose off the radiator is soft. I haven't closely examined the others. I'm assuming it's the original coolant tank, but I don't know for sure.

 

Could it be a bad thermostat?
Radiator?
Another bad tank cap?
Cracked expansion tank?

Thanks,
Carter

Carter, I had similar issues. Let me ask you this: when the low coolant light comes on, if you were to crack open the expansion tank cover, does all the coolant rush back in?

I started blowing and replacing: hoses, radiator, water-pump... at the end of the day, my bone stock, meticulously serviced, 2007 v70R that I've owned for all but three years of it's life (soccer mom was former owner)--had a cracked cylinder wall (140K @ 12 years old). The compression puts insane pressure in the cooling lines and causes crazy things to happen--like disappearing reappearing coolant levels. Personally, I heard these head gaskets are bullet-proof. If someone pulled off the head, you need to ask yourself why because it's a kind of a pain in the ass; i.e. shimming is not worth it if stock--and I stand by that even today! Going way out on a limb here, but I think your motor may have seen some abuse and now you are holding the bag

 

No, I don't think so. I haven't noticed any extreme coolant level changes.

 

Have you done block / combustion gas test? It seems to be a typical symptom of cracked block. However, who knows… If you have combustion gas in your coolant, then it is much serious than the bad cap. You want to do the simple things before you make the decision on the next step. My 2 cents…


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Have you done block / combustion gas test? It seems to be a typical symptom of cracked block. However, who knows… If you have combustion gas in your coolant, then it is much serious than the bad cap. You want to do the simple things before you make the decision on the next step. My 2 cents…

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Nope, not yet. There is no bubbling in the coolant, even warm, until it decides it's ready to go ham and boil over completely. Both the oil and the coolant that remains are clean as can be.

 

Hi all,

I have a weird problem with my cooling system that I can't seem to find answers for. I was driving home a few days ago, and after parking it, I heard gurgling coming from the engine bay. I checked, and the coolant in the expansion tank was bubbling/boiling aggressively. I didn't notice any coolant loss or leak, so I made note of it and went about my business. I was driving it yesterday and the low coolant light came on as I pulled up to my house. Basically all of the coolant (at least in the tank) had vaporized, and turned my whole engine bay into a rainforest. Step #1 was replacing the tank cap. If anything, that's made it worse. I topped the coolant off, made sure the cap was tight. This time, the upper radiator hose had blow off the radiator. I reattached it, and topped it off again. On the quick drive to see if the problem was fixed, the low coolant light had come on and gone off a couple times. I topped it off yet again and went on another drive. This time when I stopped driving, the low coolant light was on and steam was coming from under the hood. Again, the coolant in the tank was boiling. It had also puked a bunch of coolant on to the ground. I didn't have the hood open in time to see if it was boiling past the cap (as it has done previously), or had leaked out elsewhere. I put enough coolant in to drive home safely. I took the cap off of the tank, added a smidge more coolant, and ran it for a bit with the cap off in case there was some giant air bubble in the cooling system. I only saw one little bubble come up in the 5-10 minutes it was running. For additional context, it has run at perfectly normal operating temperature this whole time, and there is no shimmer in the coolant nor milky oil. No white/sweet smoke either, and the head gasket was replaced by the previous owner. The block has been shimmed, and I'm running stock boost. For those reasons I don't believe it's head gasket related, but who knows. The fan seemed to be operating normally as well. I also have not noticed leaks from anywhere besides around the tank cap when it is boiling over. Apologies for the lengthy read, but I'm trying to be as detailed as possible.

Could it be a bad thermostat?
Radiator?
Another bad tank cap?
Cracked expansion tank?

Thanks,
Carter

UPDATE:
Let it run up on ramps above dry pavement for a bit, and I've never been so happy to see a leak in my life. It was dripping slowly down the passenger side wheel well, about parallel with the expansion tank. I'm not out of the woods yet, but now I know (probably!) that the coolant isn't disappearing into the cylinders. Let's see how a replacement expansion tank does…

 

Whoop!

 

New tank is in and I’ve been driving for a couple days. Seems to be completely fixed!