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Low Coolant - But not low on coolant... Topic is solved

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, including 850 R, 850 T-5R, 850 T-5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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MathalomuleM31
Posts: 8
Joined: 04 Sep 2016, 16:51
Year and Model: 1999 S70
Location: Newburgh NY

Low Coolant - But not low on coolant...

Post by MathalomuleM31 »

Hello all!

In short: Got a new expansion tank and low coolant sensor, and now the coolant light comes on and stays on in spite of there being plenty of coolant.
More details will be of importance below...

My 1999 S70 (otherwise known as Sophie the Sweedish Fish, for her lovely red color). I recently changed the expansion tank to fix a leak which worked. But as I changed the tank, I saw that the previous owner had yanked out the coolant sensor wires and twisted them together (see pic).
That is when I realized I should replace the sensor, especially because my Low Coolant light never came on when I had low coolant... which is dangerous.
Previous owner must have done this to make sure the light never illuminated while trying to sell the car as: "Totally Not Leaking Coolant, Everything is Fine! 8) " But it wasn't fine, it had coolant leaks from the heater core and expansion tank. But I fixed all the leaks and she is good as new, however...

I got a new sensor and plugged it in... I started the car. The light came on normal pre-ignition illumination and then went off, and stayed off. :D I was happy thinking that everything was fine.
The next time I turned her on, the light came on normal pre-ignition illumination, then went out for about 3 seconds... then came back on :cry: and stays on for the entire driving time. Never goes off. I have now been driving her for about 2 weeks, and each time I start her, the light keeps coming on 3 seconds after ignition and stays on.

So what may be the problem? I checked the expansion tank's little low coolant "floater" is not stuck, it moves up and down freely. I don't understand why the sensor is reading "low coolant"

Any help?? Thank you in advance!
IMG_20160904_185605.jpg
1999 Volvo S70 GLT 2.4 Turbo

cn90
Posts: 7413
Joined: 31 Mar 2010, 09:54
Year and Model: 2004 V70 2.5T
Location: Omaha NE
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Post by cn90 »

- What brand is the reservoir: Volvo vs other?

- Check the wiring to be sure no short (may be the P.O. shorted it somewhere to sell the car).
2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+

JeffHicks
Posts: 270
Joined: 22 Oct 2013, 09:25
Year and Model: 1989 240 Wagon,
Location: United States

Post by JeffHicks »

This is a very very common problem with these cars - which is why the PO did what he did.

You wires' connection with the new sensor might be faulty. More than likely, however, it's the sensor - assuming it's not an OEM Volvo sensor. Those are known to be faulty.
1989 240 Wagon, 1999 V70 Base, 2002 XC70, 2005 V70 T5

MathalomuleM31
Posts: 8
Joined: 04 Sep 2016, 16:51
Year and Model: 1999 S70
Location: Newburgh NY

Post by MathalomuleM31 »

The expansion tank is Genuine Volvo. https://www.fcpeuro.com/products/volvo- ... 0-30741975
The Sensor is "Pro Parts Sweeden" https://www.fcpeuro.com/products/volvo- ... -uro-parts
I got both parts from FCPeuro.com

The wires seem to be in order. No visible faults. I checked all my fuses as well. If the PO twisted the wires together could that have caused a short somewhere in the system? Perhaps I should get a refund for the "Pro Parts" sensor and get a genuine volvo one?
1999 Volvo S70 GLT 2.4 Turbo

cn90
Posts: 7413
Joined: 31 Mar 2010, 09:54
Year and Model: 2004 V70 2.5T
Location: Omaha NE
Has thanked: 1 time
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Post by cn90 »

Yeah,

Use the Volvo coolant sensor, it is not expensive.

The photo you posted above, what is it?
2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+

Cees Klumper
Posts: 301
Joined: 28 Dec 2013, 13:24
Year and Model: C70 2008 T5
Location: Marina del Rey
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Post by Cees Klumper »

TS explained that the photo shows the way he found the coolant sensor wiring: tied together and not connected to the sensor.

MathalomuleM31
Posts: 8
Joined: 04 Sep 2016, 16:51
Year and Model: 1999 S70
Location: Newburgh NY

Post by MathalomuleM31 »

Okay I will make a swap for a Volvo sensor and keep you guys posted if it works. Thanks!
1999 Volvo S70 GLT 2.4 Turbo

tabletalk
Posts: 3
Joined: 11 Jul 2016, 04:05
Year and Model: 2000 v70xc
Location: Maryland

Post by tabletalk »

2000 v70xc. Coolant sensor light has stayed on since I replaced the expansion tank last December. I've since replaced the sensor 2 times (once with a Volvo sensor) and have recently replaced the expansion tank again. All new parts. Light is still on.
Any ideas?

MathalomuleM31
Posts: 8
Joined: 04 Sep 2016, 16:51
Year and Model: 1999 S70
Location: Newburgh NY

Post by MathalomuleM31 »

Thanks guys for your help! replacing the sensor with a Genuine Volvo sensor solved the problem. Everything is working fine now.
Thank you!
1999 Volvo S70 GLT 2.4 Turbo

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