H2

I want some extra cooling so I'm thinking of keeping the dual '88S4 fans between the radiator and the front of the engine.....and adding one of the larger single pusher fans onto the front of the AC cooler radiator (with fans on both front and back). I think the small fins of the AC cooler radiator impede too much air flow. I don't need a lot of extra cooling but when I push the car in slow traffic in hot weather, it gets hot. Also, once it's hot, running at highway speed it doesn't cool it enough for me. Also, since I won't need the fan all the time...but mostly because I'm a klutz at electric stuff...I'm thinking of just getting positive juice from the jumper post and grounding the fan motor...and using a simple toggle switch inside the car (in an un-noticeable place). That would work wouldn't it?

Looking for fan options, the only front pusher fan that looks like it will fit is what Carl sells at 928 Motorsports. Has anyone installed one of these on the front of the radiator? Does it clear everything? I'm a little concerned of zip tying it directly to the radiator tubing...but apparently it works OK. Anyone know of options?

Thanks for your ideas and experience.

H2

sharknoob

I just picked this up from Summit I am going electric fans soon... Maybe better then a switch to control the new fan







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Flex-a-lite 31163 $149.95
Estimated Ship Date: Today




Brand: Flex-a-lite
Product Line: Flex-a-lite Variable Speed Controllers
Part Type: Fan Switches, Thermal
Part Number: FLX-31163
Thermal Switch Style: Adjustable fan control kit
Sending Unit Style: Thread-in
Sending Unit Included: Yes
Sending Unit Thread Size: 1/4-18 NPT
Fan Quantity: Single/Dual
Adjustment Range (F): 160-220 degrees F
Relay Included: No
Wiring Harness Included: Yes
Manual Override Switch Included: No
Air Conditioning Relay Included: No
Quantity: Sold as a kit.
Notes: Variable speed control allows fan speed from 60 to 100 percent, depending on built-in thermostat setting.

Fan Control, Thermostatic, Adjustable, 160 to 220 Degrees, 1/4 in. NPT Sender,3/8 and 1/2 in. NPT Adapters,Kit

Check to make sure this part fits your application Obtain greater control over your engine's temperature.
Flex-a-lite variable speed controllers attach on or near the electric fan, sensing coolant temperature via a radiator probe or temperature sending unit. They set fan speed from 60 to 100 percent, depending on the built-in thermostat's setting. The thermostats have a range of 160-220 degrees F. The variable speed controllers allow greater control over engine temperature, which helps to reduce charging spikes and current load on the charging system. They allow a maximum load of 30 amps, and keep the fans running for 30 seconds after your vehicle is turned off.

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WallyP

If driving at highway speed doesn't cool it down, the fan won't help.

Overheating in traffic is air flow.
Overheating on the highway is coolant flow.

Alan

A single switch is a bad idea - you need a relay. The wiring needs to be big, the switch needs to be big - the wiring run will be long and voltage will be dropped even over a big wire. Don't do it.

Alan

GlenL

Harvey,

What mods are on the car?

Good advice above. To reiterate:

It sounds like a coolant, or engine, problem, not an air-flow problem.

You can get a fan controller with variable thermostat for $27.

H2

The car is stock, no mods other than the air flap system was removed by PO, perhaps not directing adequate air flow up to radiator? All the other things mentioned about overheatiing engines in Rennlist have mostly been checked, parts replaced with new, meticulously installed, etc. (thermostats, correct orientation, new gaskets, new rubber, brand new Devek style radiator, etc.). thermo opens proper, installed properly, etc. New WP 2k miles ago, metal impeller, can't detect any slippage of belt on WP roller, and so on.

So..first, I'm going to try an additional fan and putting air flaps back on..and tie them down in optimal. air deflection angle. Then, I hate to do this, I may have to pull the WP and make sure the clearance bettween impeller blades and inside plenum area is not too much, check impeller, etc. It is a Porsche WP rebuilt in Germany, sourced from Sunset).

If it's water flow, there are only two things...either something is lodged in the block....unlikely isn't it? But I can push a lot of water through the block with a hose...and the block drains have never been plugged and flow nicely.

Or perhaps the WP impeller may not be optimum size, or the PO had the WP gouge out a larger hole and it's not "grabbing" enoungh fluid. I've seen pics of the results of a WP impeller coming off and goughing things...but does anyone have a foto of perfect, undamaged one? Mine looks perfect, like it's never had issues. I put a clear see-through radiator hose on and you can see the thermo opens up on 83 degree cue...and a lot of water pushes through...so I'm having trouble thinking that it's a coolant flow problem. But maybe it's not enough?

I wanted to try a different thermstadt with a larger throughput but haven't found one. I did wire an old Therm wide open... and it seemed to help but more testing needed. I was hoping a Mercedes or some other larger orifice thermostadt would fit....none found so far.

I'd like to eliminate the WP without having to take it off. I hate broken WP bolts to deal with and I used locktite last time.

Then...I wondered if perhaps the oil could be getting hotter than it should and tranferring too much heat? How to check that? Or eliminate that possibility with a relatively cheap part replacement?

Oh yeah....all new thermostadts. Oh..and the AC is not working right now.

All ideas welcomed as I'm getting ready to throw more money and time at the issue as the weather warms up.

I drive the car daily for a couple of years or so and all's well except when I really push the car hard in the twisties with high revs, etc. Sustained 3K-5K runs get it too warm. Otherwise, it works great but not good cool enough for the track...not even close. And I hate a car that's not perfect.

Thanks,

H2

dr bob

Harvey--

Find out what the coolant temp really is, and adjust your expectations accordingly. Temp gauge reading seem to vary a lot from car to car for some reason.

Cooling system temp moves around in a range that includes "thermostat temp" at the low end, and a high number that is a balance between air temp at the radiator behind the AC condenser, and the amount of heat the engine is shedding through the coolant flow. The fans on the car will come on only when the controller senses that the coolant temp is higher than normal. Look in the WSM and see that the fans adjust speed in steps based on coolant temp. You'll also see that fans pretty much go to high when the AC is on and there is a serious load on that system. No matter, the fans go on somewhere north of when the thermostat is normally open. That's normal operation. Put in a low temp thermostat and amazingly the range between low and high changes. But the coolant temp somehow finds its balance.

Appreciate that the fans sense temp at the bottom of the radiator right at the return nozzle. The idea is that the thermostat will get to work with coolant in a range of temps managed by airflow from driving and by fan operation. The temp gauge, on the other hand, looks at coolant behind the thermostat in the water bridge, which can be different depending on how much coolant is bleeding into the bridge from the hot side. So what the gauge reads is not necesarily what's going into the engine from the radiator. Bottom line is that you need to expect that the gauge reading will vary a bit.


On to your fan options:

Adding an almost-always-on fan in front of the condenser will add airflow when you are driving slowly, but block airflow some when you are driving faster even if you have the fan turned on. Since this is a 'supplemental' fan with its own controller, the original fan will still only come on full when either radiator coolant temp or AC loads tell it to. Net effect is that your new fan will replace some normal fan load until you get to the point where the original fans would need to be at high speed despite the airflow your new fan is adding. It --might-- lower the gauge readings slightly in hot slow conditions.

I would figure out a way to piggy-back the new fan to the original controller. Belay that... I would figure out why the original cooling isn't doing what it should. If it isn't already doing what it should.

dr bob

We posted together.

Don't waste time finding a thermostat with a wider opening. The thermostat bypasses coolant flow when the engine is cold, goes closed when the coolant heats up to force flow through the radiator.

hacker-pschorr

Plenty of 928's are running just fine without the flaps installed, that's not the problem.
16V 928's never came with flaps and they have an inferior radiator to the 32V cars. I can run without fans in 95+ degree wather as long as I'm moving 20mph or faster.

$10 says your radiator is not flowing like it once did.
You cannot expect a 20 year old radiator to flow very well. Corrosion, debris from deteorating head gaskets (they all do) etc.... collect in the radiator and block flow.

Ask anyone who has pulled their side tanks and back flushed the radiator. After you see how much gunk comes out, you will wonder how the car stayed as cool as it did. A 928 radiator in perfect condition with stock fans will keep the car cool in 120+ degree weather with the A/C on while idling.

I received a good S4 radiator core from coldbeer. After a very thorough cleaning I'm having our local guru Todd weld on aluminum sidetanks. He has done this for a few rennlisters already, I'm sure he's open to do a few more.

ew928

How old is the radiator?
Has it been flow tested?
How much gunk has settled in the bottom of the radiator?
When was the radiator removed/tilted back and cooling fins cleaned/vacuumed?
Was the overflow tank coolant pressure cap replaced?

H2

Bob...
Infrared temp gun shows temp at 195 and up to coolant boils over....the temp gauge is correct. If I push really hard, I can easily get boil over. Not good.

Hacker and Ernest....
It's a brand new slightly larger than stock all aluminum radiator....Devek style...and couldn't flow faster. Louie O has an identical twin radiator installed on his Monster. I wished that it were the radiator.

Also, I'm on my 2nd new overflow tank coolant pressure cap. 100...although I tried a 150 from my 968 just to see what would happen but I chickened and took it off.

So, if the thermostadt and radiator are not obstructing flow...that leaves the block, right? But pushing all the water I can through the block with a full blast garden hose, it flows as fast as what I can put through it. It seems to be plenty open enough. And clear plastic radiator hose (from outlet to radiator) shows a lot of water throughput when the thermo opens. Maybe I should put the clear hose from the bottom of the radiator to the thermo and view that?

There's enough water circulating through that I can't imagine the relatively new water pump being the problem. Then I thought that maybe at high revs the WP/belt friction might be slipping...but TB tension is perfect.

Given this, I'm starting to wonder if the WP can't operate at full efficiency due to a larger than stock plenum in that area...but it doesn't look like it's ever been scored and it looks normal. Maybe I need to compare it with a photo of a known perfect WP/Plenum cavity?

I've been told that it couldn't be a timing issue. I installed a new belt and timing gear before I ever drove it as it had an old belt on it when I got it so it made me wonder. In my Chevy days, a timing issue could cause engine heating. I'm not sure why the Pcar couldn't have the same thing unless the brain is smarter than I think it might be.

Also, PorKen's tool shows that timing is up to spec. But maybe it's not? Or slipped a tooth or something? Runs strong as a bull....like a 928 should.

Also...I bought the testing kit to test for head gasket leak...and every test of the coolant comes up clean. And I don't lose coolant.

Additionally, compression test and leak down test numbers are great.

Chasing this problem has been frustrating.

Harvey

dr bob

OK--

Being the AR automation & controls engineer that I like to think I am, my next step would be to add a few thermocouples and see where the heat is. At least one in each radiator hose would be a start, along with one in front of and one behind the radiator. Then you can see the approach and discharge temps on both process sides of the heat exchanger. Do you happen to have a multimeter that reads type-K thermocoules? If so I may try and snag a short roll of KTC cable. With that, you can make a probe easily by just twisting the conductors together at one end, plugging the meter in at the other end. Have your trusty assistant do the wire swapping if you are driving. It would be cool to have even a hand log including engine RPM's and load conditions. Steady-state conditions for at least a few minutes make the heat balance a lot easier to manage.

H2

Bob,

I think I'm following this. My multimeter is not capable of reading type-K thermocouples but perhaps the local auto store has one with this feature. I can check tomorrow.

Then, I'd need to source KTC cable. I'm not sure I envision how the conductors would be configured and plugged it but it sounds like it's simple. Would various couples be installed...then move the multimeter from one to the other for readings?

You don't mean have my "trusty assistant" under the hood changing wires while I'm driving (down the road)? (I haven't done THAT since I was a teenager). You mean holding the rpms at a steady state...right?

It doesn't sound too complicated though.

So..by doing this, you're saying that the problem heat source could be isolated?

Are thermocouples easy to find? Expensive?

Thanks, Bob. I like the scientific method...but I usually use the shotgunning replacing parts approach.

Harvey

H2

Question...why wouldn't my infrared heat tester do the same thing? It measures temperatures just by pointing and clicking....or is that not accurate enough?

H2

ew928

What revs are you doing when the beast overheats?
Did you try increasing revs (drop a gear) to see if spinning up WP drops coolant temps?
Just a thought.