posted by
someone claiming to be macs70GLT
on
Fri Jan 11 14:16 CST 2013 [ RELATED]
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getting ready to replace the oil cooler hoses on my son's 95' 940T.
He was very low on coolant last week, when I checked I noticed the expansion tank has the Black cap, 75KPa - from previous owner. I've since purchased the Green 150KPa cap from IPD.
That Black cap would have permitted his coolant to boil off & evaporate correct?
Second - I have a replacement water pump (bought it with timing belt components not realizing it's a separate installation unlike the 240). The existing pump appears ok (~160K miles on car). How difficult is it to adequately seal a new pump?
Figured I would replace the thermostat & water pump while changing the oil cooler hoses & fluid - however I don't want to cause more problems if current pump is ok.
Thanks
Mike
95' 940T (~160K)
98' S70GLT (~195K)
88' 245 (retired @ 250K)
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If you are worried about boiling over, just put your nose near the grill, if you are losing antifreeze in the engine compartment you will smell it.
How often does your son check his fluids and tires? My tow girls had to check their cars every Saturday, or they lost their car for the week.
They both had to change a tire before my wife would let them drive alone. Chris changed a tire on her Duck's Unlimited Dodge AWD pick-up in the prairie potholes in Saskatchewan - the tire guy was properly impressed.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '72 Yamaha Rd400, '68 Honda 350-4, '12 XC70, the first 5 are mine, heh, heh, 525,000 miles put on 10 bricks James A Sousa
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The lower pressure cap will let coolant/steam out sooner/quicker that the high pressure one.
I wouldn't change a working pump, or any other part just because it has 160k, but that's just me, if it ain't broke, etc, and the "set up" is the same between 940 and 240...
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As 740-dan says, the 75kPa cap is preferred by many and is plenty adequate to prevent boiling with a properly functioning cooling system. If your car is losing coolant, a leak is more likely than boiling.
The 75kPa translates into 11 psi. I had a pressure gauge on my 240's system years ago and in even the hottest (I-5 in central California) conditions, never saw more than 8 psi. Not sure why Volvo went to the higher (22 psi) Green cap in later years, but they surely had their reasons.
The red block water pumps will often leak at the doughnut seal between the water pump and the underside of the cyl head. Of course they can also leak if the shaft seal fails, and between the block and the pump body, but that latter is rare. If it is not leaking and runs quietly I would let it be, although many would say a pump is on borrowed time at 160k.
Read over this section from the FAQ's (from the drop-down list "more" at the top of this page).
http://www.brickboard.com/FAQ/700-900/Cooling.htm
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Son's XC70, daughter's 940, my 81 and 83 240's, 89 745 (V8) and S90. Also '77 MGB and some old motorcycles
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posted by
someone claiming to be Phil Loizeaux
on
Mon Jan 21 18:40 CST 2013 [ RELATED]
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The key phrase here, as you and 740-dan say, is "properly functioning cooling system." My experience may be illustrative:
My stepson bought a '95 940 turbo a couple of years ago, and within months of that, I bought a '94 940 non-turbo. They both had black caps on the coolant tanks, and they both had original radiators. We were advised to replace the black caps with green ones, as that is the factory spec. Result? Both of our heater cores developed leaks and had to be circumvented. Then the radiator on the turbo car broke its top hose fitting.
After replacing the turbo's radiator, there have been no issues with that car. But my heater core leak started on a long trip, so I bought some stop-leak treatment and put that in the cooling system, hoping that would plug the leak in the heater core. The fix didn't last long, so I bypassed the heater core on that car as well. Both cars are without heat, not too bad in San Diego County.
I didn't realize that the real problem was a radiator with reduced flow due to the heavy-duty stop leak that I'd used. As I was driving up the Grapevine on I-5 on a warm day, headed south to home, the temp needle went to hot and stayed there, despite the higher-pressure green cap. Fortunately, a rest stop at the top of the hill cooled off the engine with the electric fan. The rest of the trip was OK, as there were no more long, steep hills.
After replacing my radiator with a $130 special from the web, my cooling fan stopped running altogether, indicating a huge improvement in cooling efficiency.
In hindsight, had I replaced both radiators and left the black caps in place, there's a chance that the heater cores would not have blown while under the lower operating pressures.
What we have here, it seems, are some crafty old-timers who replace green caps with black ones in an effort to lower stress on the 940s' cooling systems. On the other hand, we also have orthodox mechanics who religiously follow factory specifications, without recommending that all plastic-bodied radiators should be replaced after 10 years of service. Live and learn!
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re cap: You're partially right, the cap when dying out will let out coolant and not hold as much pressure, *but* that doesn't have to do with cap's pressure rating.
There is a divide of opinion as to use the higher pressure cap. Against it is that 75kpa is plenty of pressure and a higher pressure causes undue stress to hoses. After my own blown hose, I side with original pressure black cap.
Also it took me 3 tries to buy a new black cap that would last more than 1-2 months. I've posted before about this, so try a search with my username...
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Hello 740_dan,
"the cap when dying out will let out coolant and not hold as much pressure"
That is good new. I thought the the opposite would occur.
As far as caps I went to all 75 kilopascal, about 11 or 12psi since the system pressure should not top 5 to 7 lbs. I am using save the hoses and let out the steam theory. Often you don't know if your blowing your top, rather the cap, so I tied a loose 1 inch strip of rag under the cap and can't help but check it for staining every time the hood is opened.
Tom
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Thinking more about what I said, I suppose the cap could hold too much pressure, but I think it's designed to release too much pressure. I noticed my coolant going down and my expansion tank was wet even though my thermostat and hoses were fine, so my description based on that the cap can't hold proper pressure. When cooling system is working well, it takes quite a few months before more coolant needs to be added.
My mechanic for my old 240 said Volvo got cheap/lazy and only kept the green cap for replacement inventory.
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