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How To Improve the V4 Cooling System
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How-To:  V4 Cooling System Improvements

One of the most common problems with V4-motivated SAABs, particularly in warmer climates, is that of engine cooling.  In the southern United States for example, ambient temperatures commonly exceed 100F in the summer months.  Add some stop-and-go traffic and overheating is often the result.

Rob Wagner has come up with some methods of improving the effectiveness of the V4's cooling system in the SAAB 95 or 96.

Rob writes:

  If you don't have air-conditioning, and you have not made your V4 into a high compression race motor, then your cooling capacity should be OK with an electric fan.   See below for notes on fans.  A larger radiator should be your LAST modification. The 96 radiator can get pretty gummed up over the years, so you might want to check this out first.

  If your climate is very hot, or your race motor isn't cooling the way you'd like it to, you could indeed have your radiator re-cored with a longer 99 core, or use a Sonett radiator right out of the box. The -93 900 core is a little larger and I don't know if it will fit.  I have a 1994- 900 radiator in one of my 96s. By far your easiest path is to use the 96 end tanks, so you only have to remove and re-weld the lower radiator mounts a bit to either side.

  Prior to the 900, cars in general had poorly designed cooling systems, which allowed air bubbles to collect inside the motor.  In the V4, the bubbles collect around No. 4 cylinder. The 99 has one of the most illogical systems that I've ever seen, with both the inlet and outlet hoses coming out of the TOP of the radiator, and a water pump that you can't change without removing the inlet manifold and buying special tools!!  Why cling to this illogic, for the sake of originality, and big money prizes at SAAB conventions perhaps?   I am for modernizing the cooling systems, because I just love to drive hard, and don't care what they say at car shows.

  To
modernize your cooling system, the first step is to place a pressurized surge tank ABOVE the highest point of the cooling system. You can tee the bottom hose into the upper heater hose, and run the small top hose directly to the runoff nipple at the top of the radiator. 
  I have found the best fit tank to be the Volvo 240 plastic tank, because it has the same 5/8" hose nipple at the bottom, matching the heater hose. Also, this tank nestles firmly between the heater box and the wiper motor, and can be easily moved to get to the clutch master cylinder.  You don't have to tie it down, because with the bonnet closed, it is not going anywhere.

Throw away the Volvo cap and use a -93 SAAB 900 yellow cap. The original black caps were recalled. You will be running a pressure of about two atmospheres just like a 900, which has not caused me any problems for the six years that I've been doing this.   If you are using any pressurized surge tank, it is imperative to remove the filler neck on the radiator and solder the hole shut. Otherwise, air will be drawn into the system at high RPM. 'Sealing Caps' do NOT seal, please don't rely on them!

  The next area of concern is the fan.  The best alternative I've found is to cut the fan bearing and its aluminum housing off, flush with the surface of the timing cover.   With the engine in situ and the grille and radiator removed, use a cutter wheel (a $19.95 Craftsman air tool) to score around and around the aluminum.  Once you see sparks, you are through the aluminum and grinding on the steel of the bearing.  At this point, the bearing can be pulled out with hand pressure. Wipe the dust up carefully.  Then insert a 30mm freeze plug (flat end facing front) into the timing cover, lubricated with a bit of silicone.

Take the fan belt and cut it in two places so that with the ends joined, it will make a proper belt around the remaining accessories. You can then take this belt to an auto parts store for matching.  Then insert a 30mm freeze plug (flat end facing front) into the timing cover, lubricated with a bit of silicone. Drop in a flat electric fan from a 900 or a Subaru or any 12v car.

For a thermoswitch, a 900 or VW unit will work fine. I like to put it into a used 900 upper radiator hose tee... if you don't know which part I mean, look at the large upper radiator hose on the top of a 16v classic 900 engine.

  There's a metal tee in the hose with a fitting for a thermoswitch.  Normally an a/c cutoff switch goes in there, which you cannot use as a thermoswitch but the thread is the same.

  VW also offers a lower temp thermoswitch, 80C, which I also prefer.  This switch is kinder to any engine, and I use it in my 900 as well.  The switch is the same thread but set to allow the fan to come on earlier.  With this switch there is no need for a manual switch for the electric fan, in my experience... even in the rally car.

Rob Wagner (12/98)

1500cc V4 with cooling modifications (click to enlarge)

Stock V4 coolant flow (click to enlarge)

Modified coolant flow (click to enlarge)

Thermoswitch location (click to enlarge)

Coolant flow, right-side (click to enlarge)


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Last modified: February 29, 2016