225 F Engine Temp?!!!
 

Ok, I went driving my '91 911 's this weekend after doing some work on it and not driving it for a few weeks. I have nly had the car a few months and had never driven it when the air temp was above 80 degrees. No its been about 90 and I have driven it twice and the engine temps have gotten up to 225 and once close to 250. The work that I did on the car was adjust the valves, new valve covers, plugs, cap & rotor, 20w-50 oil change (1st oil change for me on the car), new heater hoses and oil breather hoses (2 on top, I discovered the front hose had been disconnected before I put the new ones on). Those changes and the air temperature outside are the only things that have changed since the car would never run over 210 before all this. Does anyone have any ideas? I didn't change anyhting else and I'm at a loss. If it always ran that hot I wouldn't know where to start but since it only ran up to 210 before something must have changed. please help.

zac

None of the tasks you have done are likely to have caused the overheating. Likely your engine is dirty or is missing some of the cooling air seals.


See:

http://forums.pelicanparts.com/porsche-911-technical-forum/74362-oil-cooler-oil-temp.html?highlight=debris

Cheers, Jim

zac, there are MANY threads in this forum which go over heat-related problems. Jim is showing you one of them, but if you look under my user name then you'll find several more with other options and possible solutions. Use the search button at the top-right corner of the web page and it will give you more advanced search options.

Your post says it's a '91, but your signature line says it's a '71. I'll assume it's a '71.

225 on a 90 degree day is totally normal, and 250 is even normal if it's being driven hard.

Does it have an auxiliary cooler?

Bruce Anderson's 911 performance handbook states that any 911 producing more than 170 hp, that doesn't have an auxiliary oil cooler, can expect a 20 degree oil temp increase for every 10 degree increase in ambient temperature. Your '71S has 180hp, so if you have no aux. cooler, then those temps are normal.

That's what I was looking for
 

Yeah, I had no idea that the air temperature could effect the engine temperature so drastically , but I couldn't think what else it could be that was giving me the higher temps. What kind of modifications could I do to make my engine run cooler? The cool collar or an oil cooler mounted in the fender well. Currently the oil system is stock w/ no auxillery coolers and I would like it to be a little ooler than it has been. How much would each of those mods reduce my oil temp? 10 degrees for the cool collar and 25 for the oil cooler? I may have a lttile project to do, alright!!!

thanks for your help

zac

Cool collar might help some, but a real auxilliary cooler would be best, by far. With a radiator-style cooler up front, including fan(s), you would have no more heat problems. Period.

If you ever have your engine out of the car, it is helpful to clean the cylinders, and have the engine-mounted oil cooler cleaned as well.

My oil temps are down since the engine overhaul, and all I did was clean those parts. With air temps in the 90s, in Seattle stop-and-go traffic (and I mean true stop-and-go), temps have gotten as high as, maybe, 230. Usually they just hug the first line on my gauge (190 degrees). A little under that line in the mornings (60-65 degrees) and sometimes a little over on the drive home (75-90 degrees, usually).

zac, I installed the cool collar and it really made no difference. I dunno if I'd waste my money on it. A '71 doesnt have the oil lines to the front, right? The front-mounted cooler is your best bet and you could start with the oil lines and trombone cooler and see what temps you get with that. I would assume that this would not cost much used. As far as 250 degrees not being a problem, I have to disagree. Oil is oil and just because it's in a 911, doesnt mean that it's now ok to be running at a temperature that oil breaks down at. You may 'expect' a temperature increase with additional h/p, but that doesnt mean it's ok.

Shoot,

I tried researching my overheating problem a bit more with no luck. I did come up with a couple more ideas as to why it ran cool before I did all the maintenance and now. I drove the car in 75 degree weather and it still over heated so I don't think the weather is a problem. The first possible idea I had was a corroded ground of the temp gage. Maybe the increased resistance of the ground is causing a foul reading of the gauge. The other idea I had was maybe when I did the oil change I loosened some 'gunk' in the engine at it has no gotten stuck in either the oil cooler or the oil feeder valve (?). Those are my two ideas, any thoughts? I just don't know what changed from before to make the engine run so hot. please help.

zac

Just a thought on this, you say you put in 20w-50? was it syn or dino? Either way thats a lot of viscousity for a 32 year old engine. Could be it just cant pump it fast enough to effectivley remove the heat, especially if its dino oil as its gonna be thick when cold. I' try a change to a lighter weight oil(no new filter required) and see if that helps. I run 15w/50-summer and 10w/40-winter in my tight 3.6....you could get by with some lighter than that for the summer. remember, oil has to be flowing to lubricate and cool, as long as the additives are good 5w/30 is whats is my chevy. my $0.02

Wow wrencher, do you really think that 20w-50 cant pump enuf volume? What about when the engine is hot, like 210+ degrees. I dunno about what you're saying. Anybody else have any opinions on the heavy-weight oils doing this?

Matt, I'm only saying in this case the only real change he made was to a heavy(heaviest) oil. It could be his oil pump just can't get up on it. What he might be seeing is the engine oil temp that never(or has trouble) pushing this oil through the filter and not circulating. Think of it this way. How long would it take to thaw a frozen garden hose by warming only the end?

ps: dude's I'm just trying to help here......

edit- It's false to believe that thicker oil cools better in fact I believe the thermal properties of oil make thinner oils better able to transfer heat.

I have Castrol GTX 20W50 in my '76 and it does fine with oil pressure and temperature. In fact, for hot climates and summer use this is probably the best viscosity grade for these older engines.

20-50 wouldn't be the reason. Besides i think (not sure) but thinker oils conduct heat better than thinner ones even though the thinner ones flow better. Besides, doesn't just about every shop, and bruce anderson recommend 15-50/20-50?

I put a Carrera front cooler on my SC and it reduced temps about 20-30 degrees. I also added a front bumper scoop at the same time. The scoop I made myself and it's probably 30-40% bigger than the currently available ones. Not sure what temps I would be running without the scoop or with the regular scoop. The scoop is a bigger deal at speed then in traffic...and deletes the front right turn signal light.

On a 90+ degree track day it sees about 230 and that's it. Before the cooler it was above 250 when I stopped the session short to let it cool.

I also put in a backdated (for my car) gauge and coordinating sender just to make sure I was reading the temps accurately.

There are kits available that will plumb an external cooler to your generation motor. They are pretty much bolt on and go.

Wrencher, sorry if it sounded like I was dissin you, I didnt mean it that way. I had heard many people who were running 20-50 without any problems and that it was actually perferred, but I wanted to solicit different opinions just to be sure. No hard feelings brother :)

Matt, no harm, no foul. I'm just relaying what I hoped was useful info. I can recall that my 3.6 does run both a little warmer and little more "sluggish" with the 20w 50 in it(used it once way back). lets face it, it takes HP to move heavier oils, work=heat, I don't know if they still do it but the nascar type guys used thin oil on qualifiing day to eek out a couple more ponies.

Hey porsheman, see what trouble you started now! - jeezzz

Oil gets thinner as it gets hotter. Low and high viscosity oils at high temperatures might become too thin and risk reducing the strength of the oil film. The better oils won't thin out as much.

Heat up some 20-50 in your SOs favorite sauce pan, then tell us how thick it stays at 200ºF. If she sees you doing this, explain to tell her you're about to make french fries.

Sherwood Lee
http://members.rennlist.org/911pcars