This is my first post to the forum (I didn't see an introduction board..)
I have a 2000 SAAB 9-3 Viggen with a checkered history that I have owned from 50k to it's current 166k. Its engine has been apart many times for various reasons (new head at 60k due to an over revving incident, new timing chain,cover, oil pump gears and head gasket between 160k and now). During my ownership, there has never been any sludge in this engine, probably due to frequent synthetic oil changes and engine disassemblies.
However, after the timing chain installation, I observed a low oil pressure light during hot idle. I had replaced the oil pressure switch sending unit so it may have merely been a higher set point on the switch. I then installed a permanent VDO mechanical oil pressure gauge to keep an eye on it. The pressure at idle was bottoming out at 7psi. I installed a new timing cover (which houses the oil pump) and oil pump. I measured the closest main and furthest rod bearings with plastigauge, and they were within spec.
The pressure at hot idle after a ~50 mile highway trip now starts at 15psi, and drops to 10psi or so after 20 minutes of stop-and-go. Ambient temperatures ranging from 20F to 40F with same results. I use Rotella T6 5w40 in this car.
I feel that this pretty low for protection of this engine. Quick online research tells me that a journal bearing turbo like my TD-04 (which is freshly rebuilt) wants at least 10psi at idle. In the summer, higher ambient temperatures may cause me not to make 10psi at idle.
So now for my question. My car is equipped with a factory oil cooler (oil to air). The oil thermostat for 9-3's fully opens at 120C (248F), and starts opening at 105C (221F). The earlier cars, including classic 900, had an oil thermostat set to 80C (176F). I know that a lot of 9-3's and 9-5's, even freshly rebuilt, tend to have idle oil pressure around 15psi. This is worrisome to many owners, and there are a lot of threads on SAAB forums on this issue. None of the threads end up with a conclusive fix.
I know that some of the 80C thermostats will fit my car. Would it be beneficial to give this a try? I recently ordered a used oil thermostat from an '88 saab 900 SPG and a new gasket. I will report back with results, unless you tell me not to do this!
Also, I'm thinking about testing this nearly 30 year old thermostat in the oven prior to installation to ensure it still works. New ones are not available in my searching.
I have a 2000 SAAB 9-3 Viggen with a checkered history that I have owned from 50k to it's current 166k. Its engine has been apart many times for various reasons (new head at 60k due to an over revving incident, new timing chain,cover, oil pump gears and head gasket between 160k and now). During my ownership, there has never been any sludge in this engine, probably due to frequent synthetic oil changes and engine disassemblies.
However, after the timing chain installation, I observed a low oil pressure light during hot idle. I had replaced the oil pressure switch sending unit so it may have merely been a higher set point on the switch. I then installed a permanent VDO mechanical oil pressure gauge to keep an eye on it. The pressure at idle was bottoming out at 7psi. I installed a new timing cover (which houses the oil pump) and oil pump. I measured the closest main and furthest rod bearings with plastigauge, and they were within spec.
The pressure at hot idle after a ~50 mile highway trip now starts at 15psi, and drops to 10psi or so after 20 minutes of stop-and-go. Ambient temperatures ranging from 20F to 40F with same results. I use Rotella T6 5w40 in this car.
I feel that this pretty low for protection of this engine. Quick online research tells me that a journal bearing turbo like my TD-04 (which is freshly rebuilt) wants at least 10psi at idle. In the summer, higher ambient temperatures may cause me not to make 10psi at idle.
So now for my question. My car is equipped with a factory oil cooler (oil to air). The oil thermostat for 9-3's fully opens at 120C (248F), and starts opening at 105C (221F). The earlier cars, including classic 900, had an oil thermostat set to 80C (176F). I know that a lot of 9-3's and 9-5's, even freshly rebuilt, tend to have idle oil pressure around 15psi. This is worrisome to many owners, and there are a lot of threads on SAAB forums on this issue. None of the threads end up with a conclusive fix.
I know that some of the 80C thermostats will fit my car. Would it be beneficial to give this a try? I recently ordered a used oil thermostat from an '88 saab 900 SPG and a new gasket. I will report back with results, unless you tell me not to do this!
Also, I'm thinking about testing this nearly 30 year old thermostat in the oven prior to installation to ensure it still works. New ones are not available in my searching.
