Massive Coolnt Loss Tonight - Advice Needed

Post by **velorider** » 26 Nov 2018, 02:19

Left the car idling, when I went into the super market tonight. When I got back dash message about low coolant. Engine temp was normal. Turned the car off and check the coolant reservoir, completely empty, about quart of coolant on the ground. Looked under the car and the plastic skid plate was dry. Coolant drops on the a-arm and the coolant cap was loose.

Towed the car home and briefly inspected it. No obvious sings of burst hoses. Refilled the reservoir, it took about a quart, no leaks, ground under the car dry.

I'll have time Tuesday to remove the plastic skip plate and inspect more throughly.

Seeking suggestions on what and where it look, with the skip plate dry it must have leaked near the overflow.

Would the fact the cap was loose indicated something?

Thanks
John

Post by **abscate** » 26 Nov 2018, 04:58

It could have blown coolant out of the loose cap. Glad you didn't overheat! Fill back up, cap on tight, and see if it leaks under pressure. If your hoses are original, it's time to replace everything on the PM model

EngineeringBloke · Post by **EngineeringBloke** » 26 Nov 2018, 18:01

Water turns to steam at 212 F (100 C). Making it a 50-50 mix with antifreeze raises the boiling point to 223 F as well as protecting against coolant freezing. The coolant pressure cap further allows the coolant to be an even hotter liquid without boiling when the cap is securely in place.

If the cap is loose, then the system is not pressurized and the coolant can boil at close to normal engine temperatures. As the liquid turns to gas (steam) in the hot engine, the gas expands and pushes coolant out of the overflow tank as you noted.

Coolant will usually continue to circulate, even as some is lost. As the steam moves around and gets to the expansion tank, the level there will drop, and the low coolant dash light will be lit. Also if the car is stopped, there will be less air cooling over the engine and the temperature will rise with more coolant loss. This probably happened in your case as you parked it in idle. The electric fan will then cool the engine and the coolant level will drop as the steam condenses back to a liquid.

As you were able to fill the system with only a quart, it seems likely that only a small proportion of the 9.3 quarts (see 2002 S60 owners manual) was lost, and so the overheating is not serious.

The loose cap appears to be the cause of the issue, but as abscate recommends, check to see if there are leaks once the coolant cap is replaced. The cap should not come loose by itself - as the system pressurizes, it locks the cap against the tank cap threads. Do you know if the coolant was recently accessed and perhaps the cap not secured?

Post by **velorider** » 26 Nov 2018, 20:02

Thanks for all the responses. I just performed a pressure test and pressure appears to be holding. I'll refill with water and drive around a bit. If everything is fine I'll flush the system and fill with a 50/50.

The cap appears to be in good shape, and I haven't opened the tank in quite a while. Would an over pressure situation cause the cap to loosen.

EngineeringBloke · Post by **EngineeringBloke** » 26 Nov 2018, 20:41

As the pressure in the system increases, it pushes the cap against its threads, securing it. The cap is not likely to come a little loose. It could explode off with very high pressure, but I would expect a hose to rupture or come free from its clamp before that.

Post by **velorider** » 26 Nov 2018, 21:13

After idling the car until it reached operating temperature, I went for a quick test drive and no leak. Definitely appears to have overflowed the overflow. I'm guessing the cap loosen some how. Hopefully just owner error, not tightening it enough. I'll keep an eye on it over the next few days.

Post by **cn90** » 26 Nov 2018, 23:06

Your car is 2002 and probably has approx. ? 180K-200K miles.
At that age and mileage, it is a good idea to get new reservoir ($55) + cap ($10).
Use only Volvo OEM brand.
Do NOT use Behr as it is made in China.

Post by **jimmy57** » 27 Nov 2018, 07:52

If the a/c was off and it was idling then the cooling fan would not come on until coolant temp went over 220 F. That seems high to us but it is the temp range most brands use for 20 years now. In workshop techs never leave the cap loose or off with car idling extended as they don't want to clean up the inevitable burped coolant mess.
If a/c is on the fan will run when a/c pressure gets to point where fan is needed for good a/c performance. The coolant will not get to boiling temp with a/c on or driving down road over 15 mph where air flows over radiator with no fan needed. The cap could have been loose for a long time without ever losing coolant in a/c use weather.

EngineeringBloke · Post by **EngineeringBloke** » 27 Nov 2018, 08:12

Delayed drop in coolant level

Sometimes additional air bubbles will be present in the system from the prior heating event, but as coolant flows from the expansion tank to the water pump and then around the system, they are pushed back out to the expansion tank. This can result in a drop in the coolant level that is not an ongoing leak. However, this should complete within a few miles of the thermostat opening up on the engine reaching operating temperature. Before the thermostat opens, air may be trapped in the engine by the closed thermostat.

You can tell that the thermostat has opened by checking the temperature gauge is at normal running level, and that the upper radiator hose is firm and is very hot (you can check it before starting the engine for a comparison). Coolant coming from the engine should be around 190 F, so touch the hose gently first so you know how hot it is. The firmness indicates coolant is under pressure and that the thermostat has opened.

Using tap water instead of distilled water

If you topped up the coolant with tap water rather than with distilled water, it is worth having the system drained and then refilled with 50/50 mix of coolant and distilled water. Tap water has minerals which can form insulating deposits on the channels the coolant passes through. This reduces the ability of the coolant to transfer heat, and if deposits are allowed to continue to build up may actually block cooling channels.

You may also take the opportunity to flush the coolant system if this has not been done in the last couple of years.

Post by **velorider** » 27 Nov 2018, 20:14

Thanks everyone for all the help. Got a few miles today without issue. Used Torque to monitor temperatures and everything looks good. I'll order new hoses and coolant from FCP soon and refresh the system soon. Meantime I'll keep an eye on the cap.