Hi, helpful folks! My 2009 C70 (124,000 mi.) has been running a little rough for the past week, then the other night we had the following sequence of events:

- No heat from heater. (My brain: ok, need a new heater valve, nbd.) Then:
- Oil light comes on. (A grocery store's right there, so I pull in, buy a quart, put it in.) Oil light goes off.
- A couple miles later, oil light and then check engine light come on. I pull oil cap; visible vapor comes out (very hot oil?), but temp gauge shows dead center.
- Half mile more to destination, park car, Lyft home, have it towed the next day.

Mechanic just called, said it was completely out of coolant and that an air bubble around the thermostat might be responsible for there being no indication of high temp. Said it's probably a cracked head gasket that allowed coolant into the cylinders until it was all gone, and that replacing the gasket, machining the current head, replacing valves, etc. will be $3,500-$4k (and a few hundred more if a new used head is needed). Codes he pulled included ECM3100, 3110, 3120 (specific cylinder misfires), ECM3410, 341c, 341d, and 2B00 (bad thermostat sensor -- ???), and 304c (knock sensor).

Questions:
- Does my mechanic's explanation sound right? Do head gaskets just fail like that in the absence of some other problem? I'm more used to high temp CAUSING a cracked head etc.
- Would you recommend replacing the gasket etc., or would it be better to find a low-mileage used engine, or even a remanufactured engine?
- In short, what's your advice for restoring this car to reliable condition without breaking the bank, and making sure it doesn't happen again?

Thanks!!

 

I'm thinking coolant temp sensor? Well I've been through this e my v70 5 cyl.I took the engine apart myself and did the job by having the head straightened.It really depends on how hot the head got.These are aluminum so in my opinion they warp quick and the heat can escape better resulting in less likely to crack imo.You do not replace valves because you didn't jump time.....so sorry that's a load of crap.....are you on a budget? Then don't replace valves.Now replacing valve seals is reasonable once head is pulled because they're cheap.ok so if head can be straightened and rings are good just throw a new head gasket and bolts and maybe a intake manifold gasket ,at it,but if it's in good shape not necessary. Get a water pipe gasket and a oil return o ring for the oil pan and maybe thermostat gasket (I just made sure my metal one was flat and I reused).....yes now is time to fix why you lost coolant obviously. But if it's crazy expensive where you are you may just do an engine swap......Good luck!

 

Something caused the car to overheat - unfortunately your car is one of the few Volvos that don't have a low coolant sensor/warning system. So - could have been a slow leak, or a fast leak from a broken radiator/hose - it's probably hard to tell with a fried head gasket as this point - but plan on some other expensive part (radiator maybe ) needing to be replaced.

The appearance of the oil light would concern me - I would caution you that there may be damage to the bottom end (crankshaft and connecting rod bearings) that may not be found until you have done the top end to the tune of $$$$. You also have a knock sensor code - Years ago after an overheating repair job such as yours - I had a car that would continually set knock sensor codes - maybe from piston damage - we never found out. Does your state require an emission inspection?

Depending on how much is melted - If the black plastic spark plug cover is melted onto the head - usually worse on the exhaust side, near cylinder 3-5 - you can bet the engine got way too hot and other damage could have occurred - If the cover is not melted/damaged - it might be ok, depending on the possible lack of oil/oil pressure damage to the bottom end.

 

I want to add something here- I went through a situation where I lost coolant and my temp gauge read normal , as I kept driving it the oil pressure light flashed and then the head warped and I lost compression.......I pulled the head and straightened it then reset the head and completed the repair and had no issue whatsoever w oil pressure.Whst happens is the head warps and you lose your seal isolating your oil galleys/veins hence the loss of oil pressure.......I e overheated three engines and never had a problem w oil pressure after the rebuilds....

 

Find a used engine, and install it . The head warping will also cause the block to warp. the head warp limit is not much so doubling the head gasket is a waste. I paid 600$ for a 70,000 mile wagon engine of greater horsepower. I did it myself and it took 5 hrs. The "Blown engine" is junk, so it's faster and cheaper to swap out the engines.