98 S70 N/A: Question about coolant and expansion tanks

[theWIFES_S70]

I flushed our coolant almost three years ago when I picked up our car. The coolant was dirty. Did it nice and slow and did it with distilled water until it ran clear. (Old coolant in there was green.) Being the "almost" purist that I am, I used Pentosin NF. What can I say, I like the color blue!

I removed the expansion tank and cleaned it out. But I couldn't remove all the grime and grit from inside it. But when I refilled the car, nothing was moving so I figured it was just stuff caked onto the expansion tank. Fast forward to today.

I had noticed a few months ago that there were black spots on my expansion tank so in one of those moves where you buy parts you don't necessarily need, I purchased a new Meyle expansion tank, fabrication date 2016. (The original one is 2013...) It's twenty bucks. It's nothing that breaks the bank. I also purchased a new Volvo coolant level sensor at the time.

Coolant level has been pretty consistent throughout the time we've owned the car. Aside from the occasional weep from the petcock which I still haven't JBWelded. I've only had to add about 4oz of coolant to the tank in the years we've owned the car.

What introduces grit and grime into a coolant system if it's supposed to be a sealed system?


Here are some pictures for comparison:
Old 2013 tank... Tank was only two years old when I picked up the car? We've put about 14K on the car so this tank has seen 14K+ miles. These Meyle pieces aren't that resilient, huh?

98_s70_old_meyle_expansion_.jpg (131.27 KiB) Viewed 2984 times

Here's the almost three-year-old Pentosin NF:
Is it supposed to turn greenish? There was a bit of grit in there, too. Is this how you know it's no longer good?

3_yr_pentosin_nf.jpg (86.27 KiB) Viewed 2984 times

Expansion tank sludge:
I'm going to keep an eye on this... It looks pretty bad. Almost ominous even. We've done long 10+ hour trips in the car. Heat is great, temp gauge stays where it's supposed to. I need to replace my heater hose lines and my heater core (preventative maintenance, no?) Would a slowly weeping heater core introduce sludge and grit into the system?

98_s70_expansion_sludge.jpg (48.4 KiB) Viewed 2984 times

New tank:
I know this is mostly cosmetic, but boy it really does look nice. I think this is a must-do if you're thinking about selling your car. Inspires confidence no?

98_s70_new_meyle_expansion_.jpg (77.11 KiB) Viewed 2984 times

[KPeirce]

The cooling system is sealed. However, that doesn't mean that the seals are going to stay eternally fresh. They deteriorate as hot coolant sideswipes them for years on end. The black stuff may be oil. Next time you sample some black stuff put a little in a dixie cup of water. If you see a rainbow its likely oil.

[June]

I had a 1998 V70 1998 through 2002 and among the car's quirks was a antifreeze smell in the ac heat system and slight coolant loss over a long period of time. The Volvo technician at my dealer who I might add worked on my mother's Volvos from sometime in the 1970s. My point is he is someone I really trusted and his advice was sound. He said we could replace the heater core and some pipes to start with as the car was under warranty, but I would likely continue to have trouble, but could replace the radiator cap with Volvo's black cap which holds half the pressure as the green and would end the trouble. He was right the smell went away and no more coolant loss.

Every car since, the 2002 S80 and my current car my 2004 S80 I replaced the green cap with the black cap for a 240 straight from the parts department before driving off the lot. None of those cars ever ran hot or had that antifreeze smell come from the ac heat system. Also my 2004 had the complete factory cooling system until this year 140k when I had the hoses and radiator replaced by Volvo. The original plastic tank is still clean and Volvo replaced the thermostat for the first time last year with the timing belt at 109k as preventive maintenance and Volvo has replaced the coolant several times over the years.

So maybe if you used Volvo coolant you would not get that crud, and maybe the black cap would take care of the slow leak. What could it hurt? I will take some pictures of my coolant jug and post them tomorrow as it is dark outside and the hurricane is dumping tons of rain at the moment. June

[wizechatmgr]

The only potential issue with the cap being half the design pressure is it lowers the boiling point of the coolant - I've had my car boil it before due to insignificant pressure and bad water/coolant ratio. Other than that, if it doesn't end up coming close to boiling temp, I see no issues with it. That said, since June lives near NAS JAX I would imagine if June doesn't overheat in the Jacksonville sun during summer, no one should. That area is HOT. Exception would be RSPI - Arizona gives hot a new meaning...

As far as sludge, etc, this can be a potential result of mixed coolants or combustion gases. Specifically mixing silicates & glycol with HOAT. As far as the grit you get, it could be from the casting process and slowly makes its way out over time or electrolysis. Keep in mind that rubber hoses tend to deteriorate from the inside out on coolant/radiator hoses. I wouldn't worry so much about the grit unless it is excessive. All else fails install a small filter on the small expansion tank hose to attempt to capture it as it returns to the tank.

Excessive example of grit:
https://www.carcomplaints.com/news/2017 ... mage.shtml

[abscate]

June...can you dig up the part number for that black cap for reference from your comprehensive service records?

I suspect the grit is parts of the water pump slowly being ground off, block castings, and internals of rubber hoses.

Drain coolant, dislodge with twizzle stick, then vacuum out, maybe?

That new coolant reservoir is pretty.

[mecheng]

I've had that sludge in my Honda, and I took very good care of it. It was completely normal, as others have mentioned it is part of the rubber in the system. I get a bit in my Volvo too; no need to worry. And yes it is normal for the fluid to change to a green color, don't judge by looks go by mileage and some say time. BTW I would trust a Volvo OEM tank over Meyle any day.

[June]

June...can you dig up the part number for that black cap for reference from your comprehensive service records?

I suspect the grit is parts of the water pump slowly being ground off, block castings, and internals of rubber hoses.

Drain coolant, dislodge with twizzle stick, then vacuum out, maybe?

That new coolant reservoir is pretty.

Sure can, off the Volvo parts ticket part number is 1357775-4 : FILLER CAP $33.94 straight from the parts department at Volvo. Keep in mind this is a factory cap for I believe a 240/740/maybe 940 not sure, probably 1990s since my 98 got one in either 99 or 2000.

I moved to North Florida from South Florida in 2005 and started using the Volvo dealer here in Jacksonville and my car has always been serviced by one particular Volvo Master Technician who has never said anything negative about the lighter pressure cap. Or tried to put the green cap back. Volvo puts a 50/50 mix of Volvos brand coolant. I don't experience after boil, overheating, or any boiling.

In fact July 2016 during the week of that heat bowl where the Midwest experienced 120° ambient temperature I was on a trip to a funeral and the car had the complete factory cooling system except the thermostat which the original never failed, and of course the coolant. All hoses, radiator, heater core were factory with 12x,xxx thousand miles and even one 120° afternoon the car idled for hours with the ac on for my dog without any problem. The hood was so hot it could not be touched but the interior was ice cold and the gage was right on half way as always. I then drove the car in traffic directly without shutting the engine down.

Also on that trip I ran the car in excess of 100 miles per hour through Oklahoma which is a big hot desert and also at that speed the dash readout said the temperature was between 110 and 120° and no boiling that day either, or did the gage ever go above half. Since the car didn't boil or overheat once, I doubt the black cap is going to cause the car to boil.

I tried to add pictures but they're not uploading right now likely because of the hurricane. I'll post some pics later once things start working again. I am currently sitting in the dark with no power and the wind is still howling outside. June

[June]

Pics of my nearly 14 year old coolant tank on my 2004 S80 T6 that has 143k. Keep in mind the coolant should be changed every couple of years or 30k once the factory fill has been removed. I understand the factory fill is pure (contamination free) which allows for a safe long change interval.

Putting non Volvo coolant is just not a good idea in my opinion as I have been told that it has is designed to lubricate the water pump and will not react to any material in the cooling system. What you are using is likely changing color as it reacts with some part of the cooling system and the sludge is likely bits of whatever is being disolved by the coolant you are using. June

[theWIFES_S70]

Thanks for all the insight everyone. Deteriorating rubber hoses. Would have to be my heater hoses (which I've been putting off for a few thousand miles...) will replace them and cut them to see if there's any deterioration. Would be interesting to find some rubber being eaten away. Thermostat's a new Wahler that I installed 3 yrs ago, too.

So June, you're a black cap aficionado? I'll definitely keep an eye on this. Like I mentioned, temperature on this car is so constant. I can't believe your expansion tank is the color it is. Do you think the Meyle tank is discolored due to an improper mixture and/or lower or higher boiloff point? This certain requires a little more research. I think I recall reading something on here about black caps. I think I remember reading that folks who race and run Water Wetter need to run black caps in P80s? I could be mistaken. Glad your safe and sound.

I just replaced the coolant in my father's 2009 Honda Accord at 80K. Oh wow, was that coolant beautiful. It had gotten darker (unlike the Pentosin NF which gets lighter) but clean as a whistle in there. Replaced with OE Honda coolant because, well, he picked it up!

Will definitely update with pictures of my heater hose lines and my heater core when I get around to the job. Thanks for the insight everyone!

[June]

The mechanic who insisted Volvo should have stuck with the black cap pressure as back in the 1990s to save technicians grief of weeping o rings and heater cores as I understand the 850/70 series in the 90s had problems with weeping heater cores. He was and is a Volvo Master Technician at my old Volvo dealer. He did that trick to solve the coolant weeping rather than ripping my dash apart. If I didn't know him personally he likely would never had altered the original equipment on a customer car in for service and would have had to replace the heater core and pipes. Also my tank has only had Volvo coolant, Maby the coolant you are using is reacting to the type of plastic the tank is made of casting the discoloration and sludge. June