Oil Thermostat Question

[Compton74]

I have a 91 7M all stock, but i did install a full flow oil cooler setup but i did not install a thermostat. I know i need to add one in there, im not looking to get blasted but i would just like to better understand what it actually does. With not running one at the moment, what negative things can happen to the engine? Id just like to know what regulating the temperature of the oil does in both positive and negative forms. I believe what Jdub is putting out is correct concise material just want to better understand how everything works together. Thanks!

 

[IJ.]

Just takes forever for the Oil to get up to operating temp, in this time you can't beat on the engine as it's not fully "expanded" and to spec.

 

[CajunKenny]

The purpose of the oil thermostat is to bring the oil up to operating temperature quicker. This is slightly more important because most of the time people install larger oil coolers, oil filters, etc... when performing Jdub's mod. This increases the car's oil capacity. Naturally, it will take longer to heat up the increased amount of oil. This is where the thermostat comes in. It prevents oil from reaching the oil cooler by recycling it back to the block for a quicker warm up. If you haven't significantly increased the car's oil capacity, then it isn't absolutely necessary.

There are no drastic consequences for not running one; but, your engine likes warmer oil a lot better than it likes cooler oil.


Well, IJ beat me to the punch.

 

[hvyman]

And if it's cold in your area its going to take a really long time as the cooler us always doing it's job.

Also pretty much all stats are like. 90/10 split so most of the oil is recirculating back into the engine but some of it is not which also warms up the oil in the cooler so when the stat opens it's not dumping cold oil onto a hot engine.

 

[Compton74]

well in most circumstances i will let the car warm up for 3-5 minutes before i drive it which means no air going through the cooler. Thank you for the replies gentleman.

 

[Supracentral]

I had a huge cooler with a defective stat back in 2002 I think it was. On a particularly cold day in February, I let my MKIII fully warm up, then got on the highway and 15 minutes later when I was pulling into a toll booth the motor had cooled down so much it went back into high idle/warm up mode while paying the toll! I had to pull over to the shoulder and let the car warm back up again before I finished my trip to the office.

I parked it until I could get a new stat. Poor flow due to cold oil can do a lot of damage. It's not worth messing with. Get that oil operating at the correct temp.

 

[CajunKenny]

What brand oil stat failed on you, Mike?

 

[Compton74]

Thanks for the input mike

 

[johnd]

great this answers my question about filtering. I thought that when the thermostat was closed that it would block all flow = no filtering, but it circulates back to engine when closed.

 

[IJ.]

Should be plumbed so 100% of the Oil goes through the filter before it gets to the T Stat...

 

[Nick M]

well in most circumstances i will let the car warm up for 3-5 minutes before i drive it which means no air going through the cooler. Thank you for the replies gentleman.

All you need to do is let it idle for 10 seconds and then drive normal. Normal is not redline or boost. The Toyota owners manual says avoid "jack rabbit starts".

 

[7M-KDL]

I do not quite understand the reason for the thermostat either. I could see it being useful back in the day or when using regular oil. With today's high tech and synthetic oils I don't really see cold flow being a problem, particularly if you are using something like 0W-30syn in a moderate climate. Even in a cool climate a 0w or 5w synthetic should have sufficient flow. The W rating is tested at or below zero degrees Fahrenheit so as long as you are not in a really cold climate(well below zero), I would think it would be fine.. Does that make sense or am I missing something?

 

[IJ.]

No T Stat the Oil takes a long time to get to operating temps/viscosities, wouldn't be a problem if you waited but most people will lean on the engine before then and this increases wear chance of damage as the engine needs to be at it's correct operating temp for clearences to be within spec..

Cold Forged piston will have slap as it hasn't expanded enough to close down the gap, give it a hard time and you'll break the skirt off usually at the Oil ring groove..

 

[7M-KDL]

Maybe you know and could help me figure it out. We are going on the basis that the engine requires SAE 30 correct? Meaning being at operating temp 190Fplus or minus would mean an oil viscosity of roughly 30(oil viscosity determined at 212F). 0W has the flow rate of a zero viscosity at 0F. Therefore, it stands to reason that at anything above zero it will have a different viscosity. My point,or question is, how do you know that at say 40-50F the 0W doesn't have the same viscosity as SAE 30 at 212F. Maybe I am over thinking or just don't fully understand the properties of oil(I am definitely no expert, just wanting to learn more).

 

[IJ.]

Post your question in the Lube section, JDub is our resident expert and will give a much better answer than I can.

 

[7M-KDL]

OK. I thought this was the lube section?

 

[hvyman]

It is or it was in here unless moved.

Just because the coolant gauge and coolant are up to temp doesn't mean the oil is. If you just start the car and drive with a oil cooler and no t stat it's going to take a long time for the oil to get up to temp.

Can use a earls sandwich plate t stat at the block or go with a mocal and mount it somewhere else. Using the sandwich plate keeps the cost down a lot more than the mocal.

 

[IJ.]

Sorry my fuckup, didn't look where we are

 

[7M-KDL]

It's all good,maybe jdub will chime in

 

[figgie]

Maybe you know and could help me figure it out. We are going on the basis that the engine requires SAE 30 correct? Meaning being at operating temp 190Fplus or minus would mean an oil viscosity of roughly 30(oil viscosity determined at 212F). 0W has the flow rate of a zero viscosity at 0F. Therefore, it stands to reason that at anything above zero it will have a different viscosity. My point,or question is, how do you know that at say 40-50F the 0W doesn't have the same viscosity as SAE 30 at 212F. Maybe I am over thinking or just don't fully understand the properties of oil(I am definitely no expert, just wanting to learn more).

You don't!

Hell even different manaufacture oils with "0W" will have DIFFERENT viscosities at the SAME temprature.
It all depends how they are acheiving 0W. but with that said. the viscosity is taken at 0 degree F for the W. Any other temps and the viscosity is variable depending on LOTS of things (base oil, formulation, additives etc).