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See the last photo of the temperature gauge: I took this today: sunny 21c on the freeway 100km/hr. Note the needle sits smack in the middle. As soon as I pulled off the freeway, needle moved to 90 (last white line) within a few minutes. Subject to checking the gauge accuracy, this tends to suggest that the cooling system is doing OK while on the move but can't cope in stop/start traffic
Perhaps I should raise this in another thread - but under acceleration the digital dash blinks and flickers. The heavier the acceleration, the more "intense" the flickering. I've studied the headlights to see if they flicker at the same time but they seem OK. Any ideas what might be causing this? A flaky alternator perhaps? Battery is only 9 months old and seems to be adequately charged.
And yesterday I parked at a shopping centre and got the right (driver's) side of the black chin-spoiler caught on some kerbing. The first 30 cms or so has come away from the tabs which secure it to the bumper and it appears the screw fixings came off too (if they were even there to begin with). Bugger.
birds-eye view of the supercharger IC radiator (with small pusher fan), A/C condenser and 928 Motorsports aluminium radiator
slightly more front-on perspective. Carl (or anyone who knows) what is that black plastic nozzle on top of the supercharger for?
A manual transmission? I thought 89 S4 models were exclusively automatic- maybe it is model year 90 onwards that changed.
On the photo the temp gauge needle sits exactly where I would hope to see it so this tends to rule out false indication and suggests you need the air blast to sustain cooling. You were doing 60 mph on your freeway at 2k rpm so the supercharger is free wheeling at those rpms and basically doing nothing other than getting in the way.
Because of the manual tranny you do not [theoretically] have to worry about a transmission cooler being in the way but as a side note, with such a power adder in the drive train you would do well to consider adding one- take some opinions on this. Porsche added a gearbox cooler to the GTS manuals- doubtless they did this for a reason- and the GTS does not have the ooopmh your setup has.
Thus from what you describe it would seem your cooling system is struggling a bit even at the modest ambients you report and presumably you were not even pushing it along by the sound of it? Look on the bright side- I was having to work on my 928 yesterday in 45C heat!
First question- did you say the louvres are working? I was advised many years ago that those things even when fully opened restrict air flow into the cooling bay- Porsche dumped them on the GTS models. Over here they wired those things fully opened and disengaged the drive mechanism- on my late S4 I removed the louvres altogether [I am not a Concoursista].
You have the 928 Motorsports radiator, the 89 model does not have the external air cooled oil cooler [more load on the radiator] and you have the intercooler in front of the main cooling matrix. Presumably you have some smaller fans filling the gaps on the back of the radiator where there is no supercharger kit?
All things considered, whereas I can understand your system will struggle when worked hard in a warm climate, I suspect that something fundamental in your cooling system is not working correctly. We have discussed options for enhancement but the basics must be right or you will simply be wasting your time.
First thing to check is the thermostat and specifically the back seal & take it from there. You might also try disconnecting the louvres and wiring them fully open.
The black nozzle on the top of the SC is for cooling. My stage 1 has a plastic hose that connects to a small blower that pumps air in there. Not sure how much good it does though. I have ran it without it. I would like to hear Carl's response to if the cooling blower is needed, or worth having.
Hey Fred, my S4 was actually sold as an '88 but I understand that it's in fact an '89 (for example, it has the digital dash).
I will investigate the transmission cooler - that's a smart idea.
Louvers: have been removed by one of the previous owners: probably when the supercharger was fitted because I don't think there would have been room for the supercharger radiator/fan.
Fans: yes spot on - there are 2 small fans in vertical formation on the passenger side rear of the 928MS radiator and a slightly larger single fan on the driver side. The centre area is unavailable to any fans because of the supercharger kit there.
Thermostat / rear seal: this is on the list when I take it in for service in 2 weeks.
Thanks Fred!
Originally Posted by FredR
A manual transmission? I thought 89 S4 models were exclusively automatic- maybe it is model year 90 onwards that changed.
On the photo the temp gauge needle sits exactly where I would hope to see it so this tends to rule out false indication and suggests you need the air blast to sustain cooling. You were doing 60 mph on your freeway at 2k rpm so the supercharger is free wheeling at those rpms and basically doing nothing other than getting in the way.
Because of the manual tranny you do not [theoretically] have to worry about a transmission cooler being in the way but as a side note, with such a power adder in the drive train you would do well to consider adding one- take some opinions on this. Porsche added a gearbox cooler to the GTS manuals- doubtless they did this for a reason- and the GTS does not have the ooopmh your setup has.
Thus from what you describe it would seem your cooling system is struggling a bit even at the modest ambients you report and presumably you were not even pushing it along by the sound of it? Look on the bright side- I was having to work on my 928 yesterday in 45C heat!
First question- did you say the louvres are working? I was advised many years ago that those things even when fully opened restrict air flow into the cooling bay- Porsche dumped them on the GTS models. Over here they wired those things fully opened and disengaged the drive mechanism- on my late S4 I removed the louvres altogether [I am not a Concoursista].
You have the 928 Motorsports radiator, the 89 model does not have the external air cooled oil cooler [more load on the radiator] and you have the intercooler in front of the main cooling matrix. Presumably you have some smaller fans filling the gaps on the back of the radiator where there is no supercharger kit?
All things considered, whereas I can understand your system will struggle when worked hard in a warm climate, I suspect that something fundamental in your cooling system is not working correctly. We have discussed options for enhancement but the basics must be right or you will simply be wasting your time.
First thing to check is the thermostat and specifically the back seal & take it from there. You might also try disconnecting the louvres and wiring them fully open.
Hey Fred, my S4 was actually sold as an '88 but I understand that it's in fact an '89 (for example, it has the digital dash).
Yours is an 89 model year car with a K in the VIN - it was imported under the pre-1/1/89 rule, so the guy who imported it had to get a letter from Porsche confirming it left the factory before then, which in turn meant it got put as an '88 on the import approval.
Yours is an 89 model year car with a K in the VIN - it was imported under the pre-1/1/89 rule, so the guy who imported it had to get a letter from Porsche confirming it left the factory before then, which in turn meant it got put as an '88 on the import approval.
It is probably like my GTS chassis- a 93 model that was delivered in August 1992- that or someone is Porsche took a bung! Not sure when GTS's were first delivered globally but I was told mine was one of the earliest ones on the road- it was ordered by the owner of the local franchise. Indeed I saw it the main dealers showroom as it was delivered and drooled extensively at the time.
All it needs is a new GTS motor that actually works and I've cracked it!
In the meantime I will just have to make do with my trusty '90 S4 motor that I keep playing around with.
This morning I dropped off my 928 to Rennsport (928 specialist workshop in Perth). They just called & said the large fan mounted to the rear of radiator was PUSHING rather than PULLING air. Surely this contributed to the cooling problem! They are rewiring it. We will see what difference it makes.
There is no undertray / bellypan on my 928 so that's next on the list.
Oil and coolant are being flushed/changed and a bottle of Royal Purple "Purple Ice" will be added to the coolant. They are checking other cooling system fundamentals. No time for anything else as they are extremely busy so I will have to bring it back in a month or so for a more thorough inspection.
When I bought new fans I ended up with 2 pushers rather than a pusher and puller. Reversed the wiring and it now pulls. Not sure if this is the best solution on curved bladed fans. Not convinced it is as efficient as having the fans spinning in the correct direction?
Waiting for a new radiator from Roger to sort some minor leaks. Had the same issue as you with heating while slow driving and have done a lot of the above but will try to change the coolant mix next to resolve. Still runs a bit hotter than the old thermo fan.
This morning I dropped off my 928 to Rennsport (928 specialist workshop in Perth). They just called & said the large fan mounted to the rear of radiator was PUSHING rather than PULLING air. Surely this contributed to the cooling problem! They are rewiring it. We will see what difference it makes.
There is no undertray / bellypan on my 928 so that's next on the list.
Oil and coolant are being flushed/changed and a bottle of Royal Purple "Purple Ice" will be added to the coolant. They are checking other cooling system fundamentals. No time for anything else as they are extremely busy so I will have to bring it back in a month or so for a more thorough inspection.
Assuming the fan was supplied with the original kit it will be a puller fan. When splicing to the original wiring harness with aftermarket fans you have to be very careful to get them spinning in the correct direction. The positive cables are easily identified as both have red in them [red/yellow & red/blue on my 928].
The fans do not do a lot once you get some speed up but having them spinning the wrong way is probably a different [not good] matter. Let's hope this makes a positive difference for you while the weather is mild.
You would have no chance in our weather at the moment [45C yesterday] - but we have a cyclone on its way [great!] and today it is a bit cloudy here so milder [now that I have finished working on my 928 for the time being].
It is reckoned that the under tray makes a difference to cooling- cannot say I have seen positive evidence to support that but I do recommend running with an aluminium under tray like the one I use.
When I bought new fans I ended up with 2 pushers rather than a pusher and puller. Reversed the wiring and it now pulls. Not sure if this is the best solution on curved bladed fans. Not convinced it is as efficient as having the fans spinning in the correct direction?
Waiting for a new radiator from Roger to sort some minor leaks. Had the same issue as you with heating while slow driving and have done a lot of the above but will try to change the coolant mix next to resolve. Still runs a bit hotter than the old thermo fan.
Norm,
G'day- Fans generally are designed as unidirectional and whereas they will work to an extent spinning the wrong way the electro/mechanical efficiency usually takes a big dump. Fan designs have improved quite a bit since your car was designed and indeed since the S4 with electric fans made its first appearance in 1987.
Good news, Juju.
I once wired my auxiliary fan backward, and the temps shot off the scale. I was at home so I shut down and figured it out. I was rewarded by a puddle of coolant on the floor from my coolant reservoir cap.
I'd say you found a major contribution to your problem.
Good luck,
Dave
Report from the mechanic was encouraging: he picked up a couple of issues (including collapsed engine mounts & a few small oil leaks) but otherwise thinks it is in very good condition.
Clutch does OK for normal driving but really isn't up to handling the power of the SC. A new clutch is on the books sometime in the future.
I added a bottle of Royal Purple "Purple Ice" to the coolant tonight and went for a 15 minute drive around the burbs. The needle on temp gauge has come down at least 5 degrees celsius, hovering around 87/88 degrees.
My proposal to relocate the intercooler radiator to the wheel well was not received optimistically. Andy from Rennsport thinks there's likely no room for it. I've seen a few installs (including the chap with the customised orange 928 in the UK) but I don't know whether these installs have fitted the same IC radiator (from 928 Motorsports). Maybe my IC radiator is bigger and won't fit. I'll speak to Carl about whether he thinks it's possible.
05-24-2015, 03:11 AM
