Using air con rad as oil cooler? - Page 2 - PeachParts Mercedes-Benz Forum

m1tch · #16 09-18-2015, 04:27 PM

I think there are quite a few variant of setups for my car anyway, I know that a lot of cars have an oil cooler built into the water radiator - mine is completely separate, also my model/setup wasn't ever sold in the US (OM606.962 but in an estate body) so it might have a few other differences - plus the fact that its never really that hot in the UK vs the US.

Its more a case of making sure that the engine oil is cooled sufficiently - although there is almost 8 litres of it!

97 SL320 · #17 09-18-2015, 06:23 PM

"" Some oil pressure systems are plumbed to where if the resistance is too much going to the cooler.... that unfiltered oil is directed into the regular system.. ""

The above makes it sound like when the cooler bypasses, oil also bypasses the filter.
My point was that when the cooler bypasses, oil filtration is unaffected as there are two bypass elements in different places in the system. The oil cooler will have a lower bypass pressure then the oil filter.

leathermang · #18 09-18-2015, 07:30 PM

When a regular car which uses a spin on oil filter and that filter gets completely clogged due to not being changed..... do you think
1. It blows the spin on filter off the car loosing the oil on the ground
2. It bypasses the filter and puts unfiltered oil into the system to keep the engine lubed
?

http://www.practicalmachinist.com/vb/general/oil-filter-bypass-not-188342/

97 SL320 · #19 09-18-2015, 09:28 PM

"" Some oil pressure systems are plumbed to where if the resistance is too much going to the cooler.... that unfiltered oil is directed into the regular system.. ""

Again I post your quote _EXACTLY_ as it appears in your post 7 ( see above. ) The . . . . are yours not mine so I have not edited or altered your post.

Your statement infers that when the cooler bypasses, the oil filter does as well using the same mechanism.

My counter is that when an oil cooler is bypassed due to thick / cold oil, this act alone does not cause unfiltered oil to reach the engine. Only the cooler is bypassed and the filter stays in the circuit unless the filter is clogged. The cooler and filter have two separate independent bypass systems set at different pressure differentials.

mannys9130 · #20 09-18-2015, 09:55 PM

I think that's a bad idea. The condenser (which is what it's called) is made for liquid refrigerant and dissolved oil to move through. The liquid refrigerant is like water. To try and push oil through it is a horrible idea.

You have a stock oil cooler already. Even though you're upgrading the turbo (and probably IP) and will be making more heat and power, you should hold off on adding anything to the stock system until you verify that the stock cooler is overwhelmed.

If it isn't overwhelmed:
Leave the condenser in place for future A/C repair
Remove the condenser for room and weight reduction
Remove it and add a good size trans cooler in its place

If the stock cooler IS overwhelmed, remove the condenser and install a bigger purpose-built oil cooler along with a good sized trans cooler.

Like you said, there are 8 liters of oil in the sump. That's a lot of heat soak capacity for the oil and the cooler adds to that greatly by rejecting heat constantly.

Like Mxfrank said, oil that's too cold is way worse than oil that is too hot.

leathermang · #21 09-18-2015, 09:56 PM

I am saying that a cooler needs a bypass in case of too much pressure or complete clogging..
and that a filter system needs exactly the same thing for the same reason..
I did not say they would have to use the same mechanism.

m1tch · #22 09-19-2015, 03:39 AM

Quote:

Originally Posted by mannys9130

I think that's a bad idea. The condenser (which is what it's called) is made for liquid refrigerant and dissolved oil to move through. The liquid refrigerant is like water. To try and push oil through it is a horrible idea.

You have a stock oil cooler already. Even though you're upgrading the turbo (and probably IP) and will be making more heat and power, you should hold off on adding anything to the stock system until you verify that the stock cooler is overwhelmed.

If it isn't overwhelmed:
Leave the condenser in place for future A/C repair
Remove the condenser for room and weight reduction
Remove it and add a good size trans cooler in its place

If the stock cooler IS overwhelmed, remove the condenser and install a bigger purpose-built oil cooler along with a good sized trans cooler.

Like you said, there are 8 liters of oil in the sump. That's a lot of heat soak capacity for the oil and the cooler adds to that greatly by rejecting heat constantly.

Like Mxfrank said, oil that's too cold is way worse than oil that is too hot.

The car is currently running without an engine oil cooler - the previous owner I think damaged the stock cooler so just had it looped. The car already has the standard transmission cooler and I can feel that the cooler does get slightly warm after a drive meaning that it must be working ok.

It was just an idea about using the air con condenser, I guess that as its thin and has very small pipes it would struggle to run oil through it - I thought I would just ask about it as its not currently being used. The aircon system must have a leak somewhere as it has no pressure - the passenger side seems to have had some sort of stone impact (or maybe an animal) as the intercooler was holed, the oil cooler was bypassed and there is a dent on the underside but only on that side.

I am tempted to simply remove it and store it for a later date if I do decide to fix it although thinking about removing the air con pump as I know that has a fair weight to it as well - not like AC is really needed in the UK!

mannys9130 · #23 09-19-2015, 05:15 AM

Definitek put that stock cooler back in place. The PO looping it and bypassing it made a bad choice.

The turbo engines have oil jets that shoot up and cool the piston from the underside. That causes the oil to heat up more than a NA engine like my 601. I don't have an oil cooler.

If you want to fix the AC, leave the condenser in place so the open tubes don't get dirt inside them. If it's the condenser itself that has a hole in it from impact, that's an easy fix.

I believe the 210s had evaporator leak issues that are expensive to fix (if the condenser isn't compromised).

m1tch · #24 09-19-2015, 05:55 AM

Quote:

Originally Posted by mannys9130

Definitek put that stock cooler back in place. The PO looping it and bypassing it made a bad choice.

The turbo engines have oil jets that shoot up and cool the piston from the underside. That causes the oil to heat up more than a NA engine like my 601. I don't have an oil cooler.

If you want to fix the AC, leave the condenser in place so the open tubes don't get dirt inside them. If it's the condenser itself that has a hole in it from impact, that's an easy fix.

I believe the 210s had evaporator leak issues that are expensive to fix (if the condenser isn't compromised).

Yeah, its not ideal, its luckily not my daily driver, also I believe that the thermostat for the engine coolant is stuck open so its over cooling at the moment. I should have the uprated oil cooler fitted in the next few weeks but won't be driving it that much anyway. I am gradually working through all of the issues on the car, should either get it up to OEM spec or uprated spec soon though.

97 SL320 · #25 09-19-2015, 09:02 AM

Quote:

Originally Posted by mannys9130

Definitek put that stock cooler back in place. The PO looping it and bypassing it made a bad choice.

The turbo engines have oil jets that shoot up and cool the piston from the underside. That causes the oil to heat up more than a NA engine like my 601. I don't have an oil cooler.

Yes, turbo motors have piston cooling jets, however if the car is driven lightly oil temps won't exceed that of a NA motor.

Put an oil temp gauge sensor where the cooler lines are looped to get accurate information before making an oil cooler decision. Remember, cars are designed to operate in a wide range of ambient temps. If the car is driven in a cold climate, additional oil cooling may not be needed.

If you don't have a oil temp gauge , use a coolant temp gauge, only the scales are different with the oil temp being higher. Another possibility is to use a coolant temp sensor that is correct for your car on the oil side then have a switch to select between the two. Be sure to have a light or other means to determine what sensor you are looking at.

m1tch · #26 09-19-2015, 09:35 AM

Quote:

Originally Posted by 97 SL320

Yes, turbo motors have piston cooling jets, however if the car is driven lightly oil temps won't exceed that of a NA motor.

Put an oil temp gauge sensor where the cooler lines are looped to get accurate information before making an oil cooler decision. Remember, cars are designed to operate in a wide range of ambient temps. If the car is driven in a cold climate, additional oil cooling may not be needed.

If you don't have a oil temp gauge , use a coolant temp gauge, only the scales are different with the oil temp being higher. Another possibility is to use a coolant temp sensor that is correct for your car on the oil side then have a switch to select between the two. Be sure to have a light or other means to determine what sensor you are looking at.

Thanks for the ideas, I can see a digital readout from the hidden menu in the climate control module, the car is currently running cool due to the thermostat being stuck open.

I will be adding in a few gauges into the car, eg a boost gauge, oil temp gauge (maybe an oil pressure gauge) and also an EGT gauge.

I would prefer to run an oil cooler as the car will be doing some drag runs and might also be sat in a queue for a bit of time as well - I know that the oil system has a thermostat so I would rather have the option for cooling the oil when needed.

What sort of oil temperatures should I be expecting/be worried about? The engine is basically stock at the moment apart from an aftermarket air filter and exhaust - so the engine has the air/boost it needs so the EGTs would be lower.

Could I perhaps run a probe through into the oil filter housing? I know that the lid is plastic so I could drill + seal a probe into there? I do have a oil filter sandwich plate but the oil filter is massive and its not a spin on filter.

97 SL320 · #27 09-19-2015, 12:46 PM

Make a T fitting and place it between the cooler lines, this offers the easiest access and the hottest oil. Be sure the sensing bulb is in the stream of oil, if it is hidden, temps will be low and slow to change.

I just noticed that you car is newer and used CAN bus, there is a small chance that switching between the two sensors will trip a trouble code due to the circuit being broken, however I'd expect a delay in triggering such a code. If tripped, the code should clear after a few drive cycles though.

Compared to coolant, oil temp is slower to rise , will be hotter by ~ 20 * F and vary with load more than coolant.

m1tch · #28 09-19-2015, 05:03 PM

Quote:

Originally Posted by 97 SL320

Make a T fitting and place it between the cooler lines, this offers the easiest access and the hottest oil. Be sure the sensing bulb is in the stream of oil, if it is hidden, temps will be low and slow to change.

I just noticed that you car is newer and used CAN bus, there is a small chance that switching between the two sensors will trip a trouble code due to the circuit being broken, however I'd expect a delay in triggering such a code. If tripped, the code should clear after a few drive cycles though.

Compared to coolant, oil temp is slower to rise , will be hotter by ~ 20 * F and vary with load more than coolant.

Thanks for the info, to fit my uprated oil cooler I needed to adapt the M22x1.5 to AN10 and the adaptor could be tapped into although the lines would only have the oil flowing through them when the oil thermostat is open.

I will probably run a separate sensor and gauge for the oil temperature - to be honest I would rather keep an eye on the oil temp rather than the coolant temp as the oil actually interacts with the engine parts.

mannys9130 · #29 09-19-2015, 10:50 PM

Quote:

Originally Posted by 97 SL320

Yes, turbo motors have piston cooling jets, however if the car is driven lightly oil temps won't exceed that of a NA motor.

Put an oil temp gauge sensor where the cooler lines are looped to get accurate information before making an oil cooler decision. Remember, cars are designed to operate in a wide range of ambient temps. If the car is driven in a cold climate, additional oil cooling may not be needed.

If you don't have a oil temp gauge , use a coolant temp gauge, only the scales are different with the oil temp being higher. Another possibility is to use a coolant temp sensor that is correct for your car on the oil side then have a switch to select between the two. Be sure to have a light or other means to determine what sensor you are looking at.

They might not run hotter than an NA engine, but only if they are stock and driven easily. He is installing a larger turbo, probably an upgraded IP, and doing racing with it. It is going to run MUCH hotter than a stock engine.

leathermang · #30 09-19-2015, 11:20 PM

Quote:

Originally Posted by 97 SL320

Yes, turbo motors have piston cooling jets, however if the car is driven lightly oil temps won't exceed that of a NA motor.

Put an oil temp gauge sensor where the cooler lines are looped to get accurate information before making an oil cooler decision. Remember, cars are designed to operate in a wide range of ambient temps. If the car is driven in a cold climate, additional oil cooling may not be needed.....

I suggest that it is not the oil temperature which you need to worry about.. but the top of the aluminum piston which is at risk... as evidenced by the design of the turbo pistons annular oil cooling design.