oil pressure again

[jamiemulhall]

hi i have a 79 sc when on the open road and engine is cooling the oil pressure light stays off but when driving through town and engine idles and gets to hot the oil light comes on even at 1.1 bar normal pressue at 4to 5000 rpm is 4+bar on the open road is fine i am using magnetec semi synthetic oil 10 w 40 (i think)
i have tried using wynns oil treatment to thicken oil up(no good) can someone sudjest a solution faulty gauge, sensor , oil pump, wrong oil need a thicker mineral oil?
in the winter i do not encounter this problem at all, only on hot days

also i am off to le mans on the pcgb site this month on the 15th midday chunnel to calais anyone want to meet up i am a newbie so any help ideas would be great

hopefully sort this oil prob out before we go ... i must arrange some breakdown cover...

thanks to rats for the info earlier i had posted message in wrong place

jamie

 

[bones]

Jamie what do you mean by too hot? If you are getting high temperature readings you should check that the front cooler is in operation it's not normal for an SC to get exteremly hot under normal driving conditions especially as we haven't had blazing hot weather yet. It's possible the external engine thermostat in the off side rear wing (front bit) is faulty and the front wing oil cooler is being shut off prematurely but tell us what temperature readings you are getting. Stop putting treatments in your oil and if I were you I'd change the oil with some fresh uncontaminated poison of your choice. Get to know oils, current favourite for SCs seems to be Silkolene Pro-S, 5-40 or 10-50, although I use Magnatec too and I'm happy with it.

 

[jamiemulhall]

thanks bones
the temp needle bearly jumps out of the bottom qtr of the gauge , heat may be the problem or the gauge is faulty but both warning lights come on red and green when idling but if i have been on a good long run every thing is as sweet as a nut and the engine at idle will be fine, then 5 mins town driving and the warning lights come on again even when i blip the engine to 2.5 bar they stay on ...?which may sudjest heat then go out i have no adverse noise and then engine performs well i will take your advice and change the oil/filter
forgive my stupidty but the 2 warning lights between the pressure and temp guage are they just pressure or temp as well?

 

[bones]

Email me and I'll send my telephone no. it is in the back of Porsche Post though, I think I can bring you up to speed. If the temperature gauge is reading normal as you suggest it is why do you think you have a temperature related problem? Although extremes of oil pressure are often consistent with extremes of oil temperature it's usually never that black and white. I don't think you have an engine problem , the fault seems likely to be elsewhere, call me and have a pen and paper handy.
I think you should check your battery voltage and the charge from the alternator at idle.

 

[jamiemulhall]

could it be the alternator belt slipping?

 

[bones]

It's possible, is it correctly adjusted? About 12"-34" horizontal deflection between the upper and lower pulleys is correct.

 

[sep4]

A green warning light at idle or slow running can be caused by a faulty oil pressure switch - not to be confused with the oil pressure sensor or oil temperature sensor, both of which are on the rear of the engine. However if the red generator light is showing as well, it may suggest something else, perhaps a charging / fan belt problem. I don't know whether the oil light would show with a slipping fan belt.

Mike

 

[bruceb]

Jamie

I had exactly the same problem on my SC when using Valvoline 10-40. I changed to the Valvoline Racing 20/50 and this cures the problem. I think its useful to remember that these engines were designed for 20/50, I think the newer lighter oils are just too thin

Bruce

 

[bones]

Can't agree with you there Bruce about newer oils not being suitable for these engines, there are plenty of older models running on fully synthetic oil without leaks and with correct oil pressure including my SC with 151,000 miles on the clock. They may be a little less quiet with thin oils in but the superior quality of modern oils protects them like never before. I had a long chat with Jamie earlier I doubt his problem is oil related. If synthetic oils dissapeared tomorrow I'd be perfectly happy to go back to using dynosaur oil but in my opinion and that of many of the people running and racing older 911s synthetics are superb oils that don't compromise oil pressure in any way.
Having said all that at my next oil change it's most likely I will be trying Silkolene PRO-S and I may well go for the 10/50 instead of the 5/40 purely on the basis of quieting the engine down but then you perhaps lose a little winter start up protection, probably marginal on an old engine like mine though and it seems to be made out of indestructable materials, it does get pampered to thorough maintenance though.

 

[jamiemulhall]

well chaps

car now in autowerk in norwich, alternator tested and not charging at idle , checked switch , not that, when at high revs will cook battery by over charging so new alternator,
this was( we believe) the cause of the erratic warning lights changing leads and distrib as well .... leads also perished, oil checked pressure fine ,engine fine,

maybe this may sort the revcounter out........

i will keep u all updated

le-mans 8 days time wwwooohooo

 

[bones]

Before you purchase an alternator check the voltage regulator as that too causes all the problems you are describing, much cheaper to fix. Your car will probably have an external regulator, so that will be surplus to requirements as the likeliehood is that they will fit a later one with a built in regulator. Ask them if they checked the regulator it could save you money and yes fixing this should cure the rev counters problem as any overall voltage problem seems to make them behave erratically.

 

[sep4]

I'll be interested to know if the alternator is Bosch or Sev Marchal , and if the regulator is external. If the regulator is at fault don't let them fit a Bosch regulator to a Sev Marchal alternator because they don't work well together. The Bosch unit is now a tiny black plastic box and cheap to buy, but the Sev is large, costly and hard to find.

 

[bones]

Hi Mike , interesting point about the alternator make. Mine's a Marchal and while I had the engine stripped down I took a look at the alternator brushes which were literally down to about 1/4" long after all those years of service. I took it to an old fashioned auto repair shop near here and they fitted new bushes while I waited for a fiver. The windings were all in tact so I guess it will go on giving good service for a few more years. If there is a Marchal alternator in there I would say it's more likely to be a regulator problem. The newer Bosch units are nothing like as long lasting as the Marchal but even there you can just replace the little inbuilt regulator if that's the problem. If I had a faulty Marchal alternator I would rather find someone to rebuild it if it could be rather than buy a new Bosch one.

 

[sep4]

Hello Pete
I had my original Sev alternator fitted with new brushes and bearings a few years ago, also for just a few pounds by some old chap who repaired starter motors and dynamos. He said that the servicable parts were the same on old Saabs and Volvos. He also gave me a larger diameter alternator bearing and adapter plate for the pulley end.
My original problem was with a dead Sev regulator and was told by a reputable Porsche repair shop to fit the later small Bosch regulator. After trying two units both showed a red generator warning light at low revs - needing a hard blip of throttle to clear the red light, I managed to get a new Sev Marchal unit - plastic bodied, not like the original aluminium bodied reg. all was well. I even tried a Paris Rhone unit which was listed for Porsche.

 

[jamiemulhall]

Hello all again
well the cars safely back at mine it was the alternator knackered giving me all those false readings also the ht cables were tracking so replaced them this has fixed the rev counter stopping it bouncing around
new distibutor cap rotor arm.
oil and filter,
also o2 was out running very lean coupled with a tune up

car now very smooth and pulls like a train
this with the 84 mm ss back box has improved the throttle responses

just some kumos on the front this saturday

car now set up for le-mans

cant wait

many thanks mat at autowerk

jamie 79 black SC