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Still overheating even after water pump

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
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erikv11
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Re: Still overheating even after water pump

Post by erikv11 » Tue Nov 29, 2016 12:58 am

broken08 wrote:UPDATE:

I went big and replaced the coolant cap, heater core, and the radiator, got an OEM thermostat in there too. Did a full flush, put in 50/50 pentofrost NF. Burped the system a couple times through heat cycling. Then I took it on a longer, harder test drive and it successfully kept temps below 225!!
I was so excited. Until I opened the hood and saw that the fluid had boiled out of the reservoir like before.
I'm at a total loss now. I guess all I can assume is that the head gasket is blown in such a way that only under serious boost it pressurizes the cooling system? In which case it's just time to push this POS off a cliff and say goodbye most likely.
You can check for exhaust gases in the coolant, get the tester from any auto parts store. It is definitely time to do that test. :shock:
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 285k
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gone: '96 NA 850 210k, '98 NA V70 182k

precopster
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Re: Still overheating even after water pump

Post by precopster » Tue Nov 29, 2016 1:39 am

Retarded valve timing causes overheating.

Just wondering if the edge of the coolant reservoir opening has deteriorated resulting in in imperfect seal; this would push temps up and result in loss of coolant. Just looking for the needle in the haystack on this one!! Yes and as erikv 11 mentioned it is time for that exhaust gases test.
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mrbrian200
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Re: Still overheating even after water pump

Post by mrbrian200 » Tue Nov 29, 2016 2:15 am

I would also consider a hairline fracture in the head or block. Highly pressurized exhaust gasses will flow out one way but viscous coolant at low pressure/vacuum compared to the power stroke, especially under hard throttle, doesn't flow back in (or not enough to detect that it's obvious).

Peak cylinder pressure in gas engines at ignition can exceed 1500psi, though for a very short time. Mean (average) pressure through the power stroke as the piston moves down is probably no less than 800psi. Then the exhaust valve opens (at those pressures) why we need mufflers. At those pressures gas will flow through a microscopic fracture easily that coolant under comparably nil coolant system pressure or engine vacuum will not.

broken08
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Re: Still overheating even after water pump

Post by broken08 » Tue Nov 29, 2016 5:27 am

I replaced the cap to rule it out but it's doing the same thing as the previous 2 caps, so I doubt that's the issue.
I'm strongly wondering if the shop actually checked for gases like they said. I have a kit coming to check myself. The timing should be good. I checked it a lot and rotated many times. The car runs smooth and quick.

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Re: Still overheating even after water pump

Post by precopster » Tue Nov 29, 2016 1:04 pm

Are the 10mm bolts on the cam sprockets hiding the slots on the cams or are they off to one side allowing you to see them?

Retarded timing can give great performance by the way.
Current cars:2002 XC70, 2006 Ssangyong Rodius (Stavic), 2006 XC90 2.5T, VW Transporter 2.5TDI

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Re: Still overheating even after water pump

Post by broken08 » Fri Dec 02, 2016 3:01 pm

It's not overheating now. I've done a few test drives and the temps are maxing out around 225 when I'm really on it. But, every time I get home I see the coolant reservoir boiling over out of the cap. So To me that really leads me to some sort of cracked block or pressure-only leak in the system. The mechanic said he checked for exhaust gasses. Theres no way a turbo could leak pressure in to the cooling lines is there?

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Re: Still overheating even after water pump

Post by broken08 » Sat Dec 03, 2016 7:20 pm

bump?

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