Installing An Aluminum VW Rabbit Radiator

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Installing An Aluminum VW Rabbit Radiator

Article by Ted Hedman

Here’s a cool radiator conversion for those hot summer days when all you can do is watch your TEMP gauge rise ever closer to the red zone. You may have heard that the aluminum VW Rabbit crossflow radiator makes a good swap for a 510, but always wondered how. Well, read on because we’ll show you how easy it is to fit this lightweight, efficient radiator into your 510.

The first step is to acquire the radiator. I was lucky enough to find the radiator you see pictured here at the local Pick Your Part wrecking yard. It was in a ‘77 Rabbit and was obviously an aftermarket replacement. It was made by Valeo, which I later found out is a quality aftermarket parts supplier for water-cooled VW’s. The Valeo part number is 883435 and is for a ‘76-’77 Rabbit or Scirocco 1.6 f.i. without A/C. You can order a new replacement radiator from VW (the part number is 171-121-253-G) but they are very pricey. The V-leo unit should run you about $100 new.


Photo 1 shows the engine side of the radiator. Note from Photo 1 that the Rabbit radiator has a thermostatic switch mounted in the side tank at position (D). This can be wired to control an electric fan. You can also see from Photo 1 that the coolant inlet (A) and outlet (B) are both located on what would be the right side (passenger side) of the car. The standard 510 radiator has the inlet offset to the left (driver’s side) of the car. This is not a problem! Thanks to Don Karry for his tip in the February ‘94 issue of 510 Again, there’s an upper radiator hose available that fits perfectly when trimmed on one end. That hose is a Gates part number 21574 or equivalent. Recently, I’ve also heard that the NAPA hose #NBH7558 and the Pep Boys hose #71189 will also work.


Since my local parts house carried only Goodyear hoses, I used the Goodyear equivalent, part number 61439. It is a 1.25” ID hose and fits the VW radiator inlet, but is a little small for the L-series thermostat housing outlet which normally requires 1.5” ID hose. I was able to fit the smaller hose over the thermostat outlet without a problem. A 15” flex hose works well for the lower radiator hose. The 1.25” ID flex hose I found seemed like it would be very hard to stretch over the slightly larger water pump inlet on the engine, so I chose the 1.5” ID hose and clamped it a little tighter to seal at the 1.25” radiator outlet. Photo 2 shows the two hoses used for this conversion. The upper hose has already been trimmed to fit.


Photo 3 shows the front side of the radiator, ready for installation. In a Rabbit, this radiator is only attached to the car at three points via pre-formed horizontal tabs built into the plastic side tanks. These points are denoted as (A), (B) and (C) in Photo 3. As you can see from the photo, I’ve added “L” brackets at (A), (B) and (C) which are used to attach the radiator to the radiator core support. The brackets are attached to the radiator using existing holes in the radiator mounting tabs.

All the brackets I used for this conversion came from an Automotive Universal Mounting Bracket kit sold by Radio Shack (catalog # 270-023A). Bracket (A) is used as is, with the bolt to attach the bracket to the core support passing through the third horizontal slot from the top (as shown in Photo 3). Bracket (B) was identical to (A) until I cut off the vertical slot so it wouldn’t interfere with the lower frame section of the chassis that runs across the front of the car below the radiator. Bracket (C) is cut to length and formed into an “L” from a piece of universal strapping that also came with the bracket kit.


Since the radiator core support is susceptible to vibration, I used Nylock nuts on all the bracket attachment bolts to minimize the chance of a bolt loosening due to vibration. Once the brackets are attached, you can place the radiator into the car at the approximate position of the old radiator (this, of course, assumes that you’ve already removed your old radiator!). Center the radiator and lower it in. Note that it will probably contact the lip around the core support opening. You may choose to bend this lip flat to move the radiator a little farther forward for more clearance between the radiator and the water pump pulley.


To reduce vibration transmitted to the radiator, and to help clear the core support lip, use compliant rubber spacers between the brackets and the core support. Stock 510 front sway bar end link bushings work great for this purpose.

Once the radiator is in approximately the correct position, test fit the upper hose to make sure it lines up with the coolant fittings at each end. When the radiator was properly positioned in my ‘72 2-door, the raised screw boss shown at position D in Photo 3 just cleared the inner lip of the core support opening and projected through at the upper right corner (as viewed from the front). I conveniently used this hole as a fourth radiator attachment point by installing the bracket shown in Photo 4 D. A closeup of this bracket also appears in Photo 6 D. The oil cooler is optional!

Once you are satisfied with the position of the radiator, mark through the holes or slots of the radiator attachment brackets with a permanent marker in preparation for drilling three holes in the core support. Use a center punch to form a dimple where you want each hole. Punch the dimple from the inside out with a good whack of the hammer, then find the dimple on the outside and punch the dimple back inwards so you can drill from the outside. I drilled holes to accept ¼-20x1” bolts. Photo 4 shows where the holes (A), (B) and (C) were drilled.


Once the holes have been drilled, install the fan on the water pump pulley before installing the radiator (unless you plan on running an electric fan.) Next, place the bolts through the brackets at (A), (B) and (C), then place a swaybar endlink bushing over each bolt and install the radiator such that the bushings are sandwiched between the brackets and the core support. Photo 5 shows how bracket A is attached with bushing in place (B and C are similar). Affix the Nylock nuts to the through bolts from the front side of the core support and tighten each until the bushing begins to bulge slightly. Your new radiator is now installed!

As mentioned earlier, I was a bit unsure about mounting the radiator at only three points, so I added the bracket shown in Photo 6 D. A screw passing through the horizontal slot from the front side picks up the raised screw hole in the boss shown in Photo 3(D). I sandwiched a rubber washer between the bracket and the radiator attachment point for compliance and vibration reduction. Although it looks like the bracket contacts the oil cooler in the photo, it does not.

Photo 7 shows the completed installation. You can see how well the hoses fit. There is about 3/8” clearance between the alternator pulley fan and the lower hose. If the radiator was positioned more towards the left side of the car, this would be a problem. There is no fan installed because I planned to go with electric fans. Note that the battery shelf has been removed. The battery now resides in the trunk. Also, in case you were wondering about the small aluminum box at the lower left corner of the photo, it’s an oil cooler thermostat.


If you are using a mechanical fan, you may be able to attach the stock fan shroud to the radiator using the attachment points on the back of the radiator that originally held the Rabbit’s electric fan assembly. There are four raised bosses with screw holes that can be seen if you look closely at Photo 1. You can also use these four mounting points to attach electric fans. I chose a pair of SPAL 7.5” electric fans from Racer Wholesale (part number SPA-00358) because they were compact enough to fit to the back of the radiator without interference with the water pump pulley by locating one on either side of the pulley. I wired them through the thermostat switch to a lighted three position on-off-on switch located under the dash. The indicator light comes on whenever the fans are on, and the three position switch allows me to bypass the thermostatic fan control switch and run the fans continuously if necessary. The hot tip is to replace the stock two-prong VW 197°F thermostat switch with a two-prong 180°F switch. I bought the 180°F switch for $8 from Velocity Sport Tuning (a water-cooled VW tuner shop). After reading the box, I found out that it is actually an aftermarket replacement for the 1.0L Chevy Chevette! It is manufactured by a company called Wahler, and the Wahler part number is 6010.87. There’s another part number that may be the original Chevette part number: 93212241. The switch is designed to turn on at a water temperature of 189°F and turn off when the temperature falls below 180°F. There’s a couple curious features about this radiator of which you should be aware of. First, there’s no nipple on the filler neck for an overflow tube. I asked my friend, who happens to be a VW expert, and he says the cap is designed to relieve pressure and overflow excess coolant around the threads of the cap when things get too hot. Strange. To allow the use of a coolant recovery tank, I ordered a Moroso aluminum filler neck tee from JEG’s (part number 710-63745, $20) that has a nipple for an overflow tube. It also allows the use of a stock 510 radiator cap or equivalent. It easily splices into the upper radiator hose after cutting a short section out of the middle. Note that if you splice the Moroso filler into the upper hose, you don’t necessarily need the exact hose mentioned above, just two “L”-shaped hoses of the right length and I.D. The other curious feature is that the Rabbit radiator doesn’t have a drain plug! I guess VW just expected you to loosen the lower hose and make a big mess! To get around that, buy a 4’ length of clear plastic hose to siphon the coolant out. It’s really very easy and clean as long as you don’t get a mouthful! Well, that’s about all there is to it! May you enjoy the ride in a cool-running 510 this summer!