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S54 Oil Cooler

    It’s not unusual to have balmy 100°F summer days here in Larryville, KS.   I’m still in mechanical puller fan delete mode. In traffic I have seen 105°C-ish coolant temperatures; a 10° rise above normal, not horrible, but I suspect some oil coolin’ action would be helpful.  To make that happen I gathered the parts to install an S54 cooling system (radiator, oil cooler, and oil filter housing, etc.); a new mechanical fan and clutch is on the agenda as well. 

     I installed a new BMW-branded (Valeo-manufactured in this case) S52 radiator last year during a cooling system refresh, but this time around, I thought I’d explore using a less expensive “OEM Quality” S54 radiator. I was tempted to go with the low price Behr, which is apparently made in South Africa, but purchased a Nissens radiator instead, which was slightly more expensive.

    Upon opening the box, I was surprised to find that rather than aluminum, the Nissens 60793 radiator for the S54-powered Z3 has a painted copper core; the Nissens plastic end tank hose connections also appear to have a beefier wall thickness than the BMW / Valeo radiator, but I may be mis-remembering and won’t know for sure until I do the swap. I’m not going to bother going into the pros and cons of copper vs. aluminum cores here, outside of a race environment, it’s generally a wash as far as automotive radiator cooling efficiency and reliability goes, and if the copper core is heavier, I’m really not concerned about a few ounces of weight difference. An OEM S54 Laengerer & Reich oil cooler fits into the Nissens radiator hangers just fine:

    Nissens 60793 S54 Radiator and Laengerer & Reich Oil Cooler

    Laengerer & Reich S54 “OEM” oil cooler (17212244084):

    Laengerer & Reich S54 Oil Cooler

    I decided to revisit the Nissens radiator selection and thought it would be prudent to take a comparative look at a Behr service replacement S54 radiator; I’m glad I choose to do so.

    The Nissens S54 radiator is a true old school three row copper core; the core consists of 40 horizontal rows in a three row thick stack. The Nissens radiator weighs 17 Lbs. The Behr S54 aluminum core radiator is basically the same width as the three row Nissens, but each of the 42 rows consists of a single tube that nearly spans the core width. The Behr weighs 10.2 lbs.

    S54 Behr aluminum core vs. Nissens copper core:

    Behr and Nissens S54 Radiators

    Aluminum core Behr full core width tubes:

    Nissens 3 tube row thick copper core:

    The Behr radiator expansion tank hose nipple has a brass tubing core, reducing the potential for catastrophic failure:

    The Nissens expansion tank hose nipple appears to be completely composite plastic:

    I’m going to go with the Behr service replacement radiator; the greater number of full core width tubes should hold more coolant, and will most likely provide better cooling even with the lower thermal conductivity of aluminum vs. copper. While the Nissens expansion tank hose nipple might hold up over time (and may also have some sort of unseen embedded metal tubing reinforcement), the obvious brass tubing insert contained in the Behr hose nipple inspires more confidence.  The 6.8 lb weight difference between the two radiators isn’t much of concern for a street car, however, less weight is another plus in the Behr column.

    I’m a bit puzzled why some people have installed S54 radiators without installing an oil cooler as a “cooling upgrade”; the S54 radiator is the same 32mm thickness as the S52 part, but the core is shorter to accommodate the oil cooler.  However, the aluminum  Behr S54 radiator does have two extra cooling tube rows (42) compared to the 40 row BMW / Valeo S52 radiator I installed during my previous cooling system refresh.  I’m skeptical that two additional tube rows provides much of a cooling improvement.

    I’m also going to remove the Motion Motorsport underbody panel and go back to the OEM air duct plastics as part of this project. Since I mildly modified my fender liners to accommodate the MM panel I’m installing a new pair of front fender liners as well.  

    My collection of parts to install the S54 oil cooler:

    S54 oil cooler parts diagram:

    In addition to the S54 radiator and oil cooler, an S54 oil filter housing is also necessary; the S54 oil filter housing has ports for the oil cooler lines and an internal thermostat to allow the oil to warm up on chilly days. The main casting is basically the same for the S52 and S54 oil filter housings and it’s a relatively easy bolt-on swap.

    The S52 hydraulic drive belt tensioner bolted onto the S54 oil filter housing with no drama; note the thermostat (circular brass slug) inside the S54 housing:

    S54 vs. S52 Oil Filter Housings

    Removing the S52 oil filter housing is pretty straightforward; the alternator needs to come out (I strongly suggest disconnecting the battery since there’s a hot 12V lead connected to the back of the alternator), and the power steering pump bolts need to be loosened. As I removed the filter housing mounting bolts, I arranged them in the same manner that they came out since they are of differing lengths; I had new bolts on hand and also wanted to match up them up with the old bolts.

    S52 block oil filter housing mounting pad; make sure that the two locating dowel pins are in place and not still attached to the old oil filter housing:

    The only real modification needed to install the S54 radiator and oil cooler was to notch the S52 fan shroud to clear the oil cooler lines:

    Modified S52 Fan Shroud

    Oil cooler line connections to the cooler:

    The bottom edge of the S52 fan shroud overhangs the top row of the S54 oil cooler reducing the efficiency somewhat; I considered trimming it back, but that edge provides mechanical reinforcement and I was concerned that removing it would overly weaken the part.  Since I am reinstalling the mechanical fan, a floppy radiator shroud would invite bad things to happen.

    With the radiator out it was a good time to replace the radiator support gaskets; the original gaskets were in good shape but had been poorly positioned at the factory and were not providing any sort of gasket sealing or cushioning action.

    New gaskets:

    The S52 air duct mated with the mysterious S54 oil cooler air duct (item 11 in the oil cooler parts diagram):

    One important thing to be aware of is that the S54 oil filter housing has two threaded ports exposed to engine oil pressure, which is not enough to accommodative the S52 oil temperature and oil pressure sensors along with the VANOS supply line; there are a couple of different solutions.  I chose to use the VANOS adapter block offered by Randy Forbes at Sports Cars Plus.  The adapter block provides an extra port for the VANOS oil line; the oil cooler connections to the filter housing and the adapter block are shown below.

    It’s not particularly obvious where to mount the oil cooler line bracket assembly (6, 8, 9, and 10 in the parts diagram) seen above; there’s a threaded hole on the back side of alternator casting for fastener 13 in the parts diagram:

    New rotating fragmentation grenade and clutch; I plan to replace the fan every few years as a maintenance item:

    We have had an unusually cool summer here in Jayhawk land with nary a 100°F day (which I am crediting to this cooling system upgrade project), so I really haven’t been able to gauge the effectiveness of adding the oil cooler; the S54 cooling system along with putting the mechanical fan back in place has been keeping the engine temp in the 93-97°C range with the A/C off.

    Update: Still no 100°F days this summer, but 95° in traffic results in a 96°C coolant temperature (A/C off) and an indicated 205-ish°C oil temperature; the oil cooler appears to have dropped the average oil temperature by 20°C or so, but I really need to move the oil temperature sensor to the oil pan for an accurate measurement.

    Indicated Oil Temperature in Traffic; 95°F Ambient