1996 850 Odd coolant leak, and dirty coolant

[granite]

My car is a 1996 automatic non-turbo 850. I bought it in February. A few weeks ago, the low coolant warning light came on intermittently when I accelerated. After a while, it came on steady, so I stopped and checked. The level was below MIN in the reservoir, by about 2/3". Enough to trigger the warning sensor. I got distilled water and topped up. It was then fine for about a week, when the same thing started to happen. I topped up again. It then seemed to lose coolant faster and faster, and I kept topping up with water. But the level never dropped below the bottom of the reservoir.

Last weekend, I did a long drive to my parents, and it was all fine. Once there, I parked and went in to get some stuff and say hi, and then run an errand in town. The warning light came on as soon as a started the engine, no more than an hour after I had parked the car. I filled more water and drove off. Parked the car for about half an hour and got the warning light again.

I drove back home the next day, and filled enough water before to take it maybe an inch above the MIN level. No warning light until 1.5 hours into the drive, when I was almost back home. I tried to check the level right away, but the pressure in the system caused hot water to spray out when I removed the cap, so I screwed it back on and waited a few hours. The fact that there was pressure in the system suggests to me that it can't be a very bad leak. Or am I wrong?

After the engine had cooled, I checked the level and it was still above the bottom of the reservoir. At no time during all this has the engine temp needle risen above level (pointing 90 degrees), so I don't think there's been any overheating.

I haven't driven the car after that, since the topping up had diluted the coolant enough to make it almost as clear as water, instead of the almost opaque, deep blue-green it was before. The fact that I have no idea what type of coolant is in the system is the reason why I only topped up with water, and didn't add coolant. I didn't want to risk mixing propylene glycol with ethylene glycol.

So today, more than a week later, I checked the level once more, and found that even left for this long, it had still not gone down to more than maybe an inch below the MIN mark. Obviously, the leak is at that level, and not much in the engine is above that level. That should help me narrow down the location of the leak. Or am I wrong in thinking that?

The second issue is that I lifted the reservoir out, to check the underside for cracks or a loose hose connection, and when I did that, the water turned a dirty brown. Before I rocked the reservoir, the water was clear. It doesn't look like oil. There is no shiny film or anything like that. It looks more like tea with milk, or lake water. With specks of loose dirt on the surface. It looked like it flowed out of the compartment with the float for the sensor. Perhaps something has rusted there? Or maybe the plastic float has degraded and started to give off crud?

Well, my question is basically if what I've described could indicate a serious problem, or if it's more likely to be a simple leak in a hose or something that is easy and cheap to fix? Finding the leak seems really difficult as there is no visible accumulation anywhere that I can see from above (and the leak is unlikely to be far down, right?), and I know from a previous car I owned what coolant residue looks like.

I intend to drain all the coolant, refill with water, drain again, and then refill with a water/coolant mix. I don't have access to running water or a floor drain where the car is, so I'll have to use collecting pans and water cans/bottles to do it...
But it would be nice to find and fix the leak first, to avoid having to waste fresh coolant.

[abscate]

The coolant capacity of the car is about 7 liters. Each time you are topping off you are replacing about 500 mL. If ypu have done ten such top-offs, ypu essentially have no coolant left. This is bad for several reasons.

The level in the reservoir does not relate to the level of the leak. The Volvo cooling system runs under about 1 ATM pressure, so leaks will spurt out once the pressure builds.

The tea with milk description is indicative of coolant mixed with oil. This can be in the cylinder head or in the radiator, where the coolant cools the transmission (ATF )fluid

None of this is good news for your motor, so your next steps have to be careful

[granite]

But the level drops down to the same level even if the car is left and not run at all. If I were to top up now, it will have leaked down to one inch below the MIN mark before tomorrow morning. So I don't buy that pressure when running is pushing the coolant out.

And the brown color seemed to come from inside the reservoir when I shook it - the fluid was clear before that.

[mika]

to expand on the above response: radiator can go bad (internal leak) and cross contaminate transmission fluid and coolant. Rememeber, radiator on our cars cools both coolant and transmission fluid, (and if its a turbo, also cools engine oil). This is the better of the two options. Other option is a head gasket leak, has car overheated? This is much harder than a new radiator.

I know that if its a head gasket, you loose power, and while in neutral, accelerating can leak to bubbles in the reservoir tank. I wish I could chime in more about the head gasket leak diagnosis (has car overheated?) but I have (knock on wood) not had this problem before.

edit: I would not worry about color before/after/whatever. You never know what dirty stuff is being sent circulating around.

just top off with water for now. You don't need any fancy equipment to chase down a coolant leak. don't overlook easy stuff like heater core (carpets will be soaked). Don't waste coolant for now, its warm anyway (even in Sweden)

[granite]

It hasn't overheated in my care, and I very much doubt it has for any of the previous owners.

It doesn't make sense for transmission fluid to be circulated all the way to the radiator. Water/coolant has much better heat capacity, and has less pumping loss, so running coolant down to the transmission makes much more sense. So any such leak would happen down there, I would imagine.

I don't think it's the heater core. It's bone dry inside the car, and no smell of coolant with heat and fan on.

[abscate]

It's much easier to put a heat exchanger in a radiator than in a transmission, so the transmission fluid gets brought up to the radiator in pretty much all cars.

These cars do not like to be overheated. It's many 100s if not 1000s to repair if cooling isn't right

[granite]

Spent an hour or so today draining the old coolant, flushing, and filling new coolant and distilled water.

The old coolant looked fine. A satin-like pale green, with no signs of oil or other contaminants. The dirty, brownish stuff, as I suspected, was just in the reservoir.

Before this, I had left the car for almost two weeks without starting the engine. No further loss of coolant below about half an inch off the bottom of the reservoir during that time.

I filled it up with ethylene glycol this time. The main reason for draining the old coolant was to make sure I know what is in there, so I can keep topping up with a coolant/water mix in the future, if the leaking continues. Before, I couldn't be sure, so I only used water.

Still not sure where the leak is, though. I noticed that the radiator drain hole in the splash guard that sits below the radiator was slightly moist, so it could be that the leak is so slow that it only hits the splash guard, evaporates and never drips onto the ground below. In that case, it probably is a leak in the radiator. A replacement radiator costs the same as 40-45 liters of ready-to-use coolant mix, which likely lasts me a year or more.

[granite]

Well, the leaking has accelerated recently, and I now know where the leak is. The seam between the alu and the plastic has opened up near the top on the passenger side. The metal tabs are bent out over 2-3 inches, and the leak is in the middle of that. I tried to bend the tabs back, but the first one broke clean off from very little force, so I gave up on that idea.

I'll be ordering a new radiator in the next week or so. Right now the coolant flows out too fast to even use the top-up method I've employed for the past weeks.

Is the AC condenser part of the radiator assembly? On my previous car, a VW Passat, the condenser was a separate, smaller radiator set in front of the engine radiator. The AC is shot anyway, so it doesn't matter...

[erikv11]

The AC condenser is a separate piece.

[abscate]

It is a three way, radiator, AC condenser, and intercooler sandwhich up front. Disconnect the radiator from the other two and drop it out the bottom, thanking the Swedish Gods you don't have ETM.

On edit...OP car is non-turbo, so no intercooler on this beast.