98 V70 NA 135K miles - missing coolant

[98v70dad]

I would also check the heater hose coupler on the cabin side, those o-rings can have annoying, slow leaks. Although they usually leak in the winter when it gets cold and they shrink. Look for a white crusty trail down the firewall. And might as well check for crust near/around the o-rings on the heater core while you are contorted like a preztel down there.

Zerex G-05 is almost exactly the same as Volvo coolant, in your shoes I think I would be topping up with that.

I know. I was going to use it initially but I could not find it anywhere in Atlanta except for the 50/50 diluted mix. I wanted to flush the system and not bother with draining the engine block. To do that I needed pure antifreeze not the already diluted stuff. I probably wouldn't do it again based on the trouble I had finding something to top off. I also had 4 bottles of different types of antifreeze in my garage and I didn't want another full gallon for topping up. I didn't realize I would eventually need all of it. I bought a 1.5 liter bottle of Pentafrost and that has worked for me. I carry it in the car. Next time I'll do things differently. Live and learn.

[98v70dad]

I think HOAT and the stuff in non-green coolants still leave white residue in retrospect. Certainly get that joint dry and clean before worrying about the CH gasket. I think your problem is simple.

I'm inclined to agree but missing coolant in a 17 year old car makes me anxious like I said earlier.

[cuhfs]

Have you pressure tested the coolant system??

[98v70dad]

I would also check the heater hose coupler on the cabin side, those o-rings can have annoying, slow leaks. Although they usually leak in the winter when it gets cold and they shrink. Look for a white crusty trail down the firewall. And might as well check for crust near/around the o-rings on the heater core while you are contorted like a preztel down there.

Zerex G-05 is almost exactly the same as Volvo coolant, in your shoes I think I would be topping up with that.

The heater core lines at the firewall don't seem to be leaking I've already checked them. I don't know what location you are referring to in this comment: And might as well check for crust near/around the o-rings on the heater core while you are contorted like a preztel down there. I paid someone to replace the heater core so I'm not familiar with the inside connections for that one if there are any.

[98v70dad]

Have you pressure tested the coolant system??

No. I don't believe that a pressure test is a good idea, especially on a 17 year old car. If you have a component (like a tiny head gasket leak) thats marginal you will go from a small problem that could possibly be lived with for awhile to a failed part that must be fixed right now as a result of the test.

This is my opinion and I know others here don't agree with me. I spent the first half my engineering career maintaining multi-million dollar machines and I don't do pressure tests due to the many unnecessary failures I've seen them cause. I've seen many perfectly good parts fail as a result of an over zealous mechanic who kept cranking up the pressure just to make sure. Even done correctly pressure tests will find your weakest link and destroy it. In normal driving you generally don't get close to the test pressure.

Bad mojo in my opinion for an old car. Others can pressure test if they chose to do so, its standard practice. Thanks for the idea though.

[cuhfs]

With all due respect, you don't have to pump it up like a balloon. Can put a few lbs in (less than the engine pressurizes to and see where it pisses from. The point is that way without the engine running noise, hot engine evaporating the small leak and moving parts you'll find your leak - distraction free.

Also living with a problem... only becomes a bigger problem in time potentially when its most inconvenient. They don't go away. Good luck.

[obayha]

The pressure check is at your own risk as you stated. How about the dye put into the coolant for color change if it has mixed with engine gases?
I have a one year old or less overflow bottle and the cap is about the same age. Cost of shipping and it's yours. Have a bottle of dye laying around I can pass your way if you want to try that also. Have the hook up for the pressure test I can loan you for the price of sending it back.
As you might be able to tell, I had a problem on my '98. Mine was all the above, plus it was a turbo, so it has those lines also.
Let me know if you need anything.
If you do the dye test and it comes out good, then a pressure test, low pressure, might not be a bad idea. Again your call.
Shane

[1ezliving4ume]

Something that is a little different about the heater core on these cars, is that it has a drain. So, if its leaking a little it will drain out and not get the carpet wet. Might check that drain hose for moisture.

[obayha]

Something that is a little different about the heater core on these cars, is that it has a drain. So, if its leaking a little it will drain out and not get the carpet wet. Might check that drain hose for moisture.

Never noticed a drain for the heater. The one for the A/C is in the way when you service the heater core, but didn't notice one for the heater. But I only had one '98 and they might be different.
Shane

[erikv11]

There is zero risk to a pressure test, done properly. Use 10 psi, that is the same or less pressure than the system sees when running hot.