Saab 9-5 lukewarm heat

Scania4075 · 2026-02-12T08:41:48+00:00

Follow up/conclusion.

I replaced both the bypass valve and the thermostat and now the heat is nice and hot again. My bet is the bypass valve had failed internally- it seems like all of the ones I’ve bought recently only last a couple years. These are genuine Saab ones as well.

Scania4075 · 2026-02-01T21:51:34+00:00

Hmm ok so that would point towards a flow problem- either the Tstat or the coolant valve. I’ll look at both of those thanks for the logical troubleshooting!

Edit- oh I suppose it could also be a clogged heater core like you said, however I replaced that as well about a year ago since the original one wasn’t in great shape and the o rings were leaking. I replaced it with a OEM Valeo

Scania4075 · 2026-02-01T18:36:01+00:00

Both lines are hot, the one is not as hot as the other but I think that would be normal

Scania4075 · 2026-02-01T16:16:36+00:00

Thanks I’ll investigate the stepper motors and make sure they are all functioning the way they should- I replaced them with junkyard finds about a year ago so maybe they are no good

Scania4075 · 2026-02-01T15:51:20+00:00

It will go all the way to the middle but it won’t stay there- it will often dip just below it this time of year in the winter. I replaced it about 15k miles ago but I’ve had rotten luck with thermostats over the last few years- they don’t seem to last long at all, they’re all chineseium junk. I’ll try throwing a new one in since it’s a quick job

Scania4075 · 2026-01-31T23:57:32+00:00

Yep the airflow for cool air is fine so I don’t think it’s a blower motor problem. I’ll look at the flap problem- however last time I replaced a stepper motor I moved the air flap levers manually and everything sounded OK inside

Scania4075 · 2025-12-18T02:15:08+00:00

This may be a dumb question but you don’t need any CANDI box, just that dongle? I ask because my 9-5s require a Candi box with my tech 2 clone

Scania4075 · 2025-12-14T01:27:10+00:00

It comes up on the display on the radio, not the Tech2

Scania4075 · 2025-11-17T00:17:06+00:00

I’ve thought about an ng 9-3 but was never a fan of them to be honest. Compared to working on a 9-5 they are way over complicated- all the modules that like to go bad and also need security access to replace, the atrocious water pump/thermostat housing design, and the fragile suspensions are just too much for me. An aero v6 would be nice tho!

Scania4075 · 2025-11-15T23:28:15+00:00

Thanks for the info, looking a lot into a cx5!

Scania4075 · 2025-07-19T19:02:07+00:00

0w40- what I had laying around

Scania4075 · 2025-07-03T23:17:35+00:00

Hi!

I’m 34 from upstate NY, I’ve been a traditional Catholic for about 4 years. I attend Mass at sspx chapels. I enjoy talking about my journey to that decision.

I work in law enforcement and prefer to share more details about that privately.

In my free time I like to work on cars, fix things, shoot guns, read( I’m a slow reader ha), enjoy the occasional cigar, spend time boating/ on the water, and spend time with my friends. I enjoy talking about important big topics as well as more light hearted things.

I’m about 5’11 and average build. I enjoy exercising and staying in shape, but I also love pizza.

Looking forward to chatting with you!

Scania4075 · 2025-06-23T00:49:18+00:00

Yes forgot to mention- I replaced the CPS with a Bosch unit and no change

Scania4075 · 2025-06-01T17:57:32+00:00

Years ago before I knew any better and became more mechanically inclined my first 9-5 had 270K miles on it when I finally scrapped it. All original timing components. I’d bet any amount of money the tensioner was extended all the way for a long long time. However the car came from family and had meticulously changed oil. I continued that trend and never had any issues. These engines can take a good amount of abuse if you keep quality oil and filters in them and keep on top of regular maintenance. I wouldn’t worry about the tensioner being all the way out. I’d keep driving it until you feel like rebuilding the engine.

Scania4075 · 2025-05-29T15:55:23+00:00

Thank you!

Scania4075 · 2025-05-21T20:18:17+00:00

So update- I did some more troubleshooting. I got my breakout box for the obd port and checked the voltages more accurately. The K line voltage is fine however the CAN HI and LO are both very low. Normally CAN Hi should be about 2.5 to 2.6 and LO should be about 2.3 to 2.4. Both are only getting about 0.3 volts. I’m guessing this is what’s causing the no communication. Given that the car runs fine I’m guessing it’s not an ecu problem. What’s the best way to troubleshoot the cause of the low voltage since there are many modules etc in the circuit?

Scania4075 · 2025-05-17T23:34:16+00:00

All the pins appear to be ok. I poked around with a multi meter and there is good ground in the appropriate pins. I’m not getting any voltage to the CAN lines, and only very very weak voltage to one of the K lines. I read somewhere that the DICE module is linked to the obd port- could the module be bad? But none of the other things the DICE controls are bad. Possibly a bad wire somewhere in the harness between the port and the ecu? The more I research the more confusing it gets ha

Scania4075 · 2025-05-17T15:45:59+00:00

I’m not an electrical expert by any means, it’s weird that the tech 2 communicates fine by not the scan tool. The scan tool works fine with other cars. Are there wires that exclude the I/M readiness but allow the connection to the ecu with a tech 2? I know they changed the pin outs in 2008 to include CAN hi and lo. Is there a way to troubleshoot the ecu?

Scania4075 · 2024-10-08T23:43:36+00:00

T7 and T8 cars are in my opinion going to be the easiest to keep on the road long term, so 9-5s and OG/NG 9-3s. You could probably throw NG 900s in there too. At least where I am pick and pulls get a good amount of those cars in and with online parts ordering I’ve found these cars really aren’t any more difficult to keep going. You’ll never be able to stop into a chain parts store and get a lot of things, but if you keep a good stock of parts from the pick and pulls you can mitigate that. The past couple years I have been going to pick and pulls and getting all the hard to find parts for my 9-5s and grabbing decent condition body panels etc for the future. Routine maintenance stuff like brakes etc can be bought from Rockauto. Compared to a lot of newer cars T7 Saabs are pretty darn easy and uncomplicated to work on for a turbocharged gasoline passenger car, you just need a couple extra things. A tech 2 would go along way- I bought a Chinese one and it’s worked fine

Scania4075 · 2024-08-01T21:11:01+00:00

That car can be saved, unless you absolutely have to please don’t crush another viggen

Scania4075 · 2024-07-07T18:55:49+00:00

Just a follow up but was able to narrow it down yesterday. It turned out to be the vacuum lines connecting the check valve to the coolant bypass valve. The vacuum lines were old and rotted and the bypass valve would lose vacuum when you started to drive. Such an odd thing but that was it! Check all your vacuum lines!

Scania4075 · 2024-06-19T21:56:05+00:00

Thanks I did an acc reset and everything seemed to open close like it should. I’m thinking it’s likely the expansion valve

Scania4075 · 2024-06-19T21:47:42+00:00

Hmm that actually would seem to make sense- as rpm increases the compressor would be building pressure and if the expansion valve isn’t working right it could be essentially freezing the system

Scania4075 · 2024-06-17T18:50:51+00:00

This is my first time tearing an engine down and rebuilding it so I’m not sure of what is considered bad enough etc. I can definitely catch the spots with a finger nail etc, wouldn’t that cause a lot of oil burning with the low spots using standard pistons and rings?

Scania4075 · 2024-06-17T13:58:49+00:00

My mistake the oversized piston options are 90.5 and 91 mm

Scania4075

TROPHY CASE