SAAB V4 Forum
SAAB V4 Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 Technical
 General Technical
 Temperature yo-yoing
 New Topic  Reply to Topic 
 Printer Friendly 
AuthorPrevious Topic Topic Next Topic 

1998teg
Starting Member

United Kingdom
6 Posts

Posted - 01 Jan 2017 :  23:26:22 Show Profile Reply with Quote
Hello, and happy new year!

With apologies for raising the well-discussed issue of temperature control, I'd welcome some wisdom on the unusual symptoms I've been seeing lately.

A little while ago I had a new triple-core radiator fitted, with a new water pump and thermostat too. Since then the temperature gauge has been all over the place.

After getting hot and sitting at the N position, it will slowly rise until it gets to half or just over half way between the N and the red zone. But then it will suddenly drop back to N. This cycle repeats pretty much whatever I'm doing on the throttle.

I can't believe this is what it should be doing. Any ideas? Might it be air in the system?

Thanks, Phillip

Betsy67
V4 Fanatic

United Kingdom
254 Posts

Posted - 02 Jan 2017 :  07:01:58 Show Profile Reply with Quote
Think I would start by putting the old thermostat back in and see what happens. Could it be in upside down ?
Go to Top of Page

UK_Sub
Moderator

United Kingdom
2106 Posts

Posted - 02 Jan 2017 :  10:58:55 Show Profile Reply with Quote
Did you bleed the system using the bleed valve situated on the heater box?
Go to Top of Page

1998teg
Starting Member

United Kingdom
6 Posts

Posted - 02 Jan 2017 :  11:28:57 Show Profile Reply with Quote
Thanks for the suggestions. The work was done at a garage so I can't vouch for the bleeding. It's something I'll check when I can.
Go to Top of Page

green96v4
V4 Fanatic

Canada
295 Posts

Posted - 02 Jan 2017 :  12:50:53 Show Profile Visit green96v4's Homepage Reply with Quote
Hi Phillip

My temp gauge has always sat just above N and wouldn't the movement be just the thermostat opening and closing? (it could be that your temp gauge wasn't moving as much before as the old rad/pump/stat were sludged up with old age and now the new parts are allowing the waterways to "breathe" easier?)
Go to Top of Page

Derek
V4 Guru

United Kingdom
1779 Posts

Posted - 03 Jan 2017 :  12:38:19 Show Profile Reply with Quote
The orientation of the thermostat is apparently critical if you go by the manual. The domed cross bar on the top can be pressed down and distorted by the lid when bolted down. This will effect how it opens and closes. This distortion might correct itself when you take the lid back off. I've not read of anyone having this problem so they must be going by the book or just lucky. However the garage may not know about this and so might have put it in the wrong position. It may be that only certain brands of thermostat have a problem. Cross bar should be across the car (at right angles to the crank) for peace of mind.
Go to Top of Page

pchristy
V4 Guru

United Kingdom
1737 Posts

Posted - 04 Jan 2017 :  09:38:31 Show Profile Reply with Quote
When you say the needle suddenly moves, do you mean its flickering? If so that suggests an electrical fault rather than the cooling system.

I had the same on mine, and traced it to the multi-pin connector on the back of the instrument. Giving this a wiggle - or better, remove and replace it - should provide a cure. Its a poor earth caused by slight corrosion on the pins. If you watch carefully, you can see it affects the fuel gauge as well, but not so noticeably.

--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
Go to Top of Page

Fliptop
V4 Fan

United Kingdom
147 Posts

Posted - 04 Jan 2017 :  14:30:17 Show Profile Reply with Quote
Also check the wire on the temp sensor on the stat housing - they can get loose (it's just a spade connector on a round terminal) and vibrate, causing the needle to flicker.

Running and bodging Saabs since the dark ages...
Go to Top of Page

1998teg
Starting Member

United Kingdom
6 Posts

Posted - 05 Jan 2017 :  22:13:29 Show Profile Reply with Quote
Good suggestions all, thank you.

Regarding the sudden fall; I wouldn't describe it as a flicker. From the N position the temperature rises slowly and steadily up to a point whereupon it will fall back to the N at a much faster rate.
Go to Top of Page

Zagato
V4 Mad

United Kingdom
742 Posts

Posted - 06 Jan 2017 :  08:13:57 Show Profile Reply with Quote
Mine did as you describe also before it came off the road. I need to put a new thermostat in, just scared of sheering off the probable seized bolt, gonner start soaking it in plus gas now and undo it in the summer lol!

96L
9000 Aero
9-3
9-5

Edited by - Zagato on 06 Jan 2017 08:15:03
Go to Top of Page

melle
V4 Guru

United Kingdom
2270 Posts

Posted - 06 Jan 2017 :  11:46:14 Show Profile Visit melle's Homepage Reply with Quote
1998teg: What you experience is just the thermostat opening, nothing unusual. Your engine probably has a thermostat with an opening temp of about 89degC fitted, replace with a "colder" (82/83degC) thermostat if it bothers you. I never bleed the cooling system using the bleed valve on the heater box and I've never had issues. Just put the heat on max for a mile or so after filling the system, works a treat.

Zagato: Replace the bolts with studs once you're at it.

Derek: I think it's nigh on impossible to fit the thermostat in the wrong position.

www.saabv4.com

Edited by - melle on 06 Jan 2017 11:58:52
Go to Top of Page

1998teg
Starting Member

United Kingdom
6 Posts

Posted - 08 Jan 2017 :  15:08:25 Show Profile Reply with Quote
melle: thank you for a very re-assuring reply. I shall try to trust that everything is just fine - but I might change to a lower-rated thermostat when it's next convenient. I'll also do the heater trick in case there's any residual air in the system.
Go to Top of Page
 Previous Topic Topic Next Topic 
 New Topic  Reply to Topic 
 Printer Friendly 
Jump To: 
Snitz Forums 2000
SAAB V4 Forum© 2000-04 Snitz CommunicationsGo To Top Of Page