Thermostat closes and opens at a set temp. Once it closes, there is no oil flow thru the cooler or drain back into the sump. It's basically a backflow preventer. This isn't rocket science mates. 
-
Welcome to N-cars.net - the largest Hyundai N car forum. Check out the model specific sections below and scroll down for country specific forums. Scroll down for i30 N, Ioniq 5 N, i20 N, Veloster N and Kona N forums! Check out the i30 N Bible Here!
Engine Oil Cooler
- Thread starter Ghost
- Start date
Thermostat closes and opens at a set temp. Once it closes, there is no oil flow thru the cooler or drain back into the sump. It's basically a backflow preventer. This isn't rocket science mates.
It's the other way around. It OPENS if the temp is lower than the set one. It CLOSES if it's higher. So it cannot be used as a backflow preventer. Right?
Sorry if the questions appear dumb or smth, I just wanna understand it
I've got mine laying next to me and I can see that it's open at room temp.
It depends upon what type of thermostat is utilized. A oil filter plate thermostat works differently then a High-Flow Engine Inline Oil Cooler Thermostat. One if part of the actual filter plate the other is inline on the hoses. The plate thermostat has to close to allow oil from the plate assembly to the cooler. When it's open, it will only flow thru the filter and OEM system.
When the engine oil temp rises to over what the thermostat is rated for it will open and bypass to the oil cooler. You don't want the oil running thru the cooler when it not up to operating temp. It will bypass the oil cooler until the valve is thermostatic valve is open by the preset temp. Once temps are reduced below the preset thermostat temp it will again close and bypass the oil cooler.
However there will be a small volume (less than 10%) of oil permitted to pass the thru to the oil cooler to eliminate air pockets and prevent cold fluid trapped in the cooler from shocking the system.
If the thermostat closes there is no oil (less than 10% ) passing thru the cooler. If it's open, it allows a full volume of oil to pass thru the cooler, until oil temp reduces to below the preset thermostat temp. Otherwise, no oil will pass thru the oil cooler until the valve is open. There are two reasons oil flows thru the oil cooler;
1. Oil pressure with increased volume and pressure at greater rpms
2. Thermostat opening, with greater heat from the circulating oil.
Opening or closing is simply selective terminology and is neither valid or invalid, unless you're specifically talking about flow from the sump or to the sump. If the thermostat doesn't operate at the preset temp, (closed or open) no oil will pass thru the oil cooler.
Think of the thermostatic valve as a faucet. If it's shut , no water is flowing. If it open the water is flowing. There's still pressure behind the faucet but it's not flowing except in the actual system behind the faucet.
When the engine oil temp rises to over what the thermostat is rated for it will open and bypass to the oil cooler. You don't want the oil running thru the cooler when it not up to operating temp. It will bypass the oil cooler until the valve is thermostatic valve is open by the preset temp. Once temps are reduced below the preset thermostat temp it will again close and bypass the oil cooler.
However there will be a small volume (less than 10%) of oil permitted to pass the thru to the oil cooler to eliminate air pockets and prevent cold fluid trapped in the cooler from shocking the system.
If the thermostat closes there is no oil (less than 10% ) passing thru the cooler. If it's open, it allows a full volume of oil to pass thru the cooler, until oil temp reduces to below the preset thermostat temp. Otherwise, no oil will pass thru the oil cooler until the valve is open. There are two reasons oil flows thru the oil cooler;
1. Oil pressure with increased volume and pressure at greater rpms
2. Thermostat opening, with greater heat from the circulating oil.
Opening or closing is simply selective terminology and is neither valid or invalid, unless you're specifically talking about flow from the sump or to the sump. If the thermostat doesn't operate at the preset temp, (closed or open) no oil will pass thru the oil cooler.
Think of the thermostatic valve as a faucet. If it's shut , no water is flowing. If it open the water is flowing. There's still pressure behind the faucet but it's not flowing except in the actual system behind the faucet.
Last edited:
there may be more than one type of thermostats, however in this thread we've been talking about Mocal thermostats, in particular the one's integrated into the oil filter sandwich plate. I think the Airtec oil cooler utilizes the sandwich plate with name "M-OTSP1" (not 100% sure tho).
And for those you can specify which position is open and which is closed. The video I linked in the earlier post explains it pretty well imo.
Open means flow through the oil cooler is optional. The Thermostat opens when the oil temp is lower than the temp specified for the thermostat.
Closed means oil has to flow through the oil cooler. The Thermostat closes when the oil temp is higher than the temp specified for the thermostat.
For me, this means the thermostat cannot be used as a backflow-preventer. This also means the oil will ALWAYS flow out of the Airtec oil cooler except when you mount it the other way around, like @TarmoT did.
Even a backflow-preventer-valve between oil cooler and sandwich plate won't fix this.
Sure there are; inline and plate style thermostats.
Yes for a plate style you're correct, if you're not coming from the sump, it would be open to pass thru the filter. Closed for flow to the cooler.
Backflow preventer allow flow from one direction and denies it to the other. It can be utilized to keep the oil from the cooler being washed back into the sump, when pressure has ceased. They're generalized utilized on race cars and bikes. where a thermostat is impractical. They're on the inflow side oil cooler from the sump.
Yes for a plate style you're correct, if you're not coming from the sump, it would be open to pass thru the filter. Closed for flow to the cooler.
Backflow preventer allow flow from one direction and denies it to the other. It can be utilized to keep the oil from the cooler being washed back into the sump, when pressure has ceased. They're generalized utilized on race cars and bikes. where a thermostat is impractical. They're on the inflow side oil cooler from the sump.
Ok gotcha.
Regarding the backflow preventer:
Would you say installing 2 backflow preventers, one per oil line, would help here? If they are pressure-regulated this should help shouldn't it?
I am a little bit concerned here (maybe just my lacking understanding) because if they allow oil flow from one direction and not from the other, the oil could still just flow back to the engine using the same oil line it also uses when the engine is running? Meaning we could block off flow on one oil line but not on the other. Correct?
No, on the backflow preventers. When the thermostat is opened, there won't be any backflow from the thermostat plate. You'll still be draining out of the outlet side of the cooler if it's right side up. It's not really that much of an issue. It's only a half a liter of oil and will be held in the cooler and the oil line that feed back to the MOCAL plate.
Don't be concerned about this amount of oil even if it was constantly in the sump. If it was a much larger cooler and carried more than a liter more of oil, yes.
Don't be concerned about this amount of oil even if it was constantly in the sump. If it was a much larger cooler and carried more than a liter more of oil, yes.
No, on the backflow preventers. When the thermostat is opened, there won't be any backflow from the thermostat plate. You'll still be draining out of the outlet side of the cooler if it's right side up. It's not really that much of an issue. It's only a half a liter of oil and will be held in the cooler and the oil line that feed back to the MOCAL plate.
Don't be concerned about this amount of oil even if it was constantly in the sump. If it was a much larger cooler and carried more than a liter more of oil, yes.
okay, and comparing this to the airtec cooler where the fittings are on the lowest side of the cooler?
This would then drain out the cooler completely, right?
Probably, but it's only a half a liter at most. That's not that much in the grand scheme of things. I'd imagine the hose on the inlet side to oil cooler will be holding at least .25 liter. So .25 liter flowing back into the sump, will hardly amount to more than a hair overfull. That's not going to hurt anything.
Remember, these are GDI's and are prone to blowby and fuel dilution in the sump. So they're designed to be a little higher on the dipstick with this in mind.
Remember, these are GDI's and are prone to blowby and fuel dilution in the sump. So they're designed to be a little higher on the dipstick with this in mind.
Probably, but it's only a half a liter at most. That's not that much in the grand scheme of things. I'd imagine the inlet side to oil cooler will be holding at least .25 liter . So .25 lor so flowing back into the sump, will hardly amount to more than a hair overfull. That's not going to hurt anything.
Remember, these are GDI's and are prone to blowby and fuel dilution in the sump. So they're designed to be a little higher on the dipstick with this in mind.
Mhmm okay that helps
Meaning the last 3 pages of this thread are now full with infomation whis is more or less irrelevant to the question in the beginning
At least we learned something along the way
Certainly, but it's the journey that counts, not the end result isn't it? If I'd have said it's only a half liter more of oil in the sump from the beginning, there would still have been more questions.
If I'd have said it's only a half liter more of oil in the sump from the beginning, there would still have been more questions.
True, thanks for answering my questionsCertainly, but it's the journey that counts, not the end result isn't it?
Through this thread and the associated googling I learned a lot about how thermostat in take-off sandwich plates work
You're always welcome. That's what we are here for anyway. It does help to educate and inform. Sometimes it's just better to quote then go into a big explanation. I started utilizing oil coolers back in 1974. So there wasn't much information available even on the internet. Mostly in motorcycle and hot rod magazines.
The internet has its merits sometimes but it's also a source of trouble.
Sometimes it's just better to quote then go into a big explanation. I started utilizing oil coolers back in 1974. So there wasn't much information available even on the internet. Mostly in motorcycle and hot rod magazines. The internet has its merits sometimes but it's also a source of trouble.
I am not 100% sure that Mocal thermostatic sandwich plate works like described in video.
It has thermostatic bypass system not thermostatic cut off system built in.
It means that under marked temperature bypass is activated (oil is bypassing oil cooler) and when engine oli will reach settled temp, bypass will close off (oil is going thru oil cooler).
I made short research and found that information:
It has thermostatic bypass system not thermostatic cut off system built in.
It means that under marked temperature bypass is activated (oil is bypassing oil cooler) and when engine oli will reach settled temp, bypass will close off (oil is going thru oil cooler).
I made short research and found that information:
ah yeah sure gotcha, the oil won't run to the cooler until the bypass is closed of, as it will always take the shortest route.
//Offtopic
Little example. Guy changed the reverse light from halogen to LED.
Other guy crashed in his back because "he was blinded" (even if the guy in front wasn't going in reverse).
Car has been checked -> not factory lights -> insurance did not pay.
Germany isn't Europe when it comes to laws and regulations in traffic.
Believe me, Germany is another level
Also asked my "exhaust guy" about this topic. He said we are going into way too much detail with this discussion. 0.5L more oil in the engine is not a problem as the crankshaft should not yet touch the pool of oil when spinning and therefore not cause any issues for the engine (e.g. increased blow-by etc.).
Instead we should focus our attention on the oil pressure.
Because: If you mount the oil cooler with the fittings down, oil would flow out of the cooler. This would lead to an irregular oil pressure as the oil would have to get back into the cooler at some point. This could cause more stress on the oil pump in the long term.
Therefore he recommended mounting the oil cooler in the way @TarmoT did it - fittings facing up.
The oil would not leave the cooler and you would have a static oil pressure in your car.
Even during an oil change he said that our cars come with plenty of oil capacity, 0.5L that do not get changed will not cause any harm in the long term, because our service happens so frequently. If you want to sleep well at night, you could do an additional oil change right after the mandatory one, but this is not necessary in his opinion.
Instead we should focus our attention on the oil pressure.
Because: If you mount the oil cooler with the fittings down, oil would flow out of the cooler. This would lead to an irregular oil pressure as the oil would have to get back into the cooler at some point. This could cause more stress on the oil pump in the long term.
Therefore he recommended mounting the oil cooler in the way @TarmoT did it - fittings facing up.
The oil would not leave the cooler and you would have a static oil pressure in your car.
Even during an oil change he said that our cars come with plenty of oil capacity, 0.5L that do not get changed will not cause any harm in the long term, because our service happens so frequently. If you want to sleep well at night, you could do an additional oil change right after the mandatory one, but this is not necessary in his opinion.
