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v90 overheating 900

posted by  hans747 on  Wed Nov 25 15:59 CST 2009
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last visit: Mon Feb 7 07:55 CST 2011
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This is 1998 V90 with 127k miles, and a green plastic resevoir cap. Right when I was finishing up a 10-hour road trip with the family today, the car overheated. I'm looking for advice, so I'll start from the beginning.

3 years ago, replaced the factory radiator because the plastic hose neck was cracking

2 years ago, replace temp sensor (failed) and the thermostat (since i was already in there anyway)

3 weeks ago, replace aftermarket radiator (leaking) with an aluminum aftermarket radiator

2 weeks ago, cap on the radiator's oil cooler port (this is a universal-type radiator) blows off while wife is waiting to pick up son from school. She shuts down car immediately. Replace cap with a beefier one, refill with whatever rad fluid I have in the trunk plus water, and car runs fine. however, I notice that there is always a faint odor of radiator fluid after shutting the car down. I see no drips, no water in oil, and no oil in water. Car is using a little bit of rad fluid, but I figure it has to do with high water ratio (evaporation????), so I top off the tank with coolant.

Yesterday, I drove for 5 hours. Coolant level did not move a hair.

Today, Drive 4 hours. Stop to refuel. Coolant level has not moved. Drive 6 more hours on the highway. After 30-minutes in stop/go traffic, I see some steam coming from the hood. I look at temp guage, and it's almost in the red. Pull over, and pop the hood. The resevoir cap sounds like a soda bottle being slowly opened ("pfffffffffffffffffffftttttttttttttt"). after about 10 minutes, I find an old cowboy hat on the side of the road. I put it over the resevoir cap and slowly twist it open. lots of bubbling, lots of steam, and lots running over. I grab a jug of coolant/water mix out of the trunk and refill. The car takes 1 gallon plus 24-oz of bottled water (sorry dear, but the car is thirstier than you right now). The temp needle is standing in the middle, so I start it up and drive again. No more overheating problems for the remaining 45 mins.

Hears what I'm going to check tomorrow:
1. Fan operation: if not working, is the fan, the fuse, the relay, or the sensor the biggest culprit? Suggestions on how to test? Where is the sensor for the fan located?

Any suggestions would be helpful. Is there something else I'm overlooking?








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    v90 overheating 900

    uid 11021's pic
    posted by  dewfpo on  Sun Nov 29 05:57 CST 2009
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    last visit: Thu Oct 23 18:34 CST 2014
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    The blue/green reservoir cap is actually a 1.5 bar cap (22 psi). The higher the PSI, the higher the boiling point of the coolant. Next time it overheats, don't remove the cap until it cools down. Releasing the pressure may cause the coolant to flash boil.

    DEWFPO
    --
    1998 S90 083,228 and 1995 964 154,100








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    v90 overheating 900

    posted by  trichard on  Wed Nov 25 23:30 CST 2009
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    last visit: Fri Oct 24 05:52 CST 2014
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    no matter what the problem turns out to be replace the green cap with a low pressure black one. the green caps run the system at 2 atmospheres of pressure while the black ones run less than 1. there is absolutely no gain from running a high pressure cap unless you spend all your time in bumper to bumper traffic in the heat.

    high pressure caps unduly stress the system for obvious reasons.

    the human equivalent is having 195/120 versus 110/65 blood pressure. one gives you a stroke or heart attack while the other gives you the chance to grow old intact.







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      v90 overheating 900

      posted by  hans747 on  Thu Nov 26 00:47 CST 2009
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      last visit: Mon Feb 7 07:55 CST 2011
      [RELATED]

      thanks, I will definitely try that. I alwayws wondered why this car had such an intense cap on the resevoir. that thing holds a lot of pressure.








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    v90 overheating 900

    posted by  david hunter on  Wed Nov 25 17:08 CST 2009
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    last visit: Mon Jun 30 22:10 CST 2014
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    The fan is controlled by the ECU according to engine temp via an electronic speed controller mounted near the rad (no relay). It is difficult to know when it's on but you can hear it at idle. It should come on when AC is selected and should also cycle on at idle if temp increases sufficiently

    There are diagnostics tests that can be run but I have lost my documentation on the subject, others may know about this.

    Have you changed the thermostat?
    --
    David Hunter








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      v90 overheating 900

      posted by  hans747 on  Thu Nov 26 00:50 CST 2009
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      last visit: Mon Feb 7 07:55 CST 2011
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      i replaced the T-stat a couple years ago. what's strange is that the car when straight from running perfect to boiling over in a matter of minutes. does a bad t-stat just go out like that? or does it slowly start to fade.








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        UPDATE --FIXED 900

        posted by  hans747 on  Mon Nov 30 03:40 CST 2009
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        last visit: Mon Feb 7 07:55 CST 2011
        [RELATED]

        When the sun came up the next day, the problem was clear: the plug for the electrical fan had come loose (wasn't all the way into its socket). Thank Odon that i didn't fry the engine with such a simple problem.








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          UPDATE --FIXED 900

          posted by  spook on  Mon Nov 30 16:25 CST 2009
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          last visit: Fri Oct 24 08:06 CST 2014
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          Dear Hans747,

          May this find You well. This happened to me ('94 940). Happily ambient temps were low (50ºF / 10ºC), the trip was short, and the fan kicked-in.

          I replaced the plug and the grommet with Volvo brand parts (cost was US$5). I lubrciated the plug with dishwashing liquid, and used a large water pump pliers to seat it fully.

          I used heavy brass wire to secure the plug. I put the wire under brass fitting to which is attached the top transmission coolant pipe. I looped the wire around a radiator fin, and twisted the wire ends. I smoothed the twisted ends with a file and bent them out of the way.

          This will ensure the plug does not again back-out.

          Hope this helps.

          Yours faithfully,

          Spook








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        v90 overheating 900

        posted by  david hunter on  Thu Nov 26 02:38 CST 2009
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        last visit: Mon Jun 30 22:10 CST 2014
        [RELATED]

        A thermostat can fail open, fail closed, intermittently, anytime, even when new. I consider putting in a new thermostat a diagnostic, you cannot really test it, see it or feel it so just replace it, easy and cheap.
        --
        David Hunter







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