Overheating on the highway. 76, 2.0 Options

[SVG223]

My 914 overheats on the highway. I had concerns about the air flap, but I think the thermostat has broken and it stays in the open position. I thought something might be clogging the fan but it looks clear. I wonder about the heater air hose that goes over the motor. It could be blocking some air possibly. I may try to tie it out of the way. After exiting the highway and stopping at a stopsign the idle was extremely low, I was surprised it was still running. I turned the engine off for a while and it ran better after it cooled down. Any ideas would be appreciated.

[Superhawk996]

Did it actually go into the red zone? If not then it technically is not overheating.

How long did it take to get to that position?

I see that you are new to the World. Is the car new to you, do you have history with the car ? . . Has it run much cooler in the past and a rapid surge got your attention?

Is the timing set properly?

[JamesM]

This could be SO many things its hard to find a place to start, especially on a 76. Need a lot more information here.

It could be cooling air flow related, but it could also be related to the tune of the engine or overall engine condition.

I think its worth noting though that the gauge you are looking at is showing your oil temps which are not always the best indicator of if your engine is killing itself or not (im always more concerned with head temps) especially given the vagueness of that particular gauge setup. It may not even be an actual problem unless this is a noticeable change from where it was previously running.

FYI your engine is the only one I have ever seen in 25+ years of 914s that has an intact grommet on the thermostat cable, so I have to ask, has this engine ever been out of the car? If not (and given the fact that im looking at a small leaf in your fan, I would venture to guess that you could have a lot of crud in your engine fins/oil cooler.

[Superhawk996]

This could be SO many things its hard to find a place to start, especially on a 76. Need a lot more information here.

FYI your engine is the only one I have ever seen in 25+ years of 914s that has an intact grommet on the thermostat cable, so I have to ask, has this engine ever been out of the car? If not (and given the fact that im looking at a small leaf in your fan, I would venture to guess that you could have a lot of crud in your engine fins/oil cooler.

(IMG:style_emoticons/default/agree.gif)

Good eye on the grommet. (IMG:style_emoticons/default/shades.gif)

[SVG223]

Did it actually go into the red zone? If not then it technically is not overheating.

How long did it take to get to that position?

I see that you are new to the World. Is the car new to you, do you have history with the car ? . . Has it run much cooler in the past and a rapid surge got your attention?

Is the timing set properly?

I don't think it quite made it to the red zone, it almost touched it. While it was still hot the idle was 200 rpm it's normally 1000 rpm. I'm guessing loss of compression from the heat, don't know.
It took about 20 minutes.
The car is new to me, got it in winter.
I just had the valves adjusted, not sure if he checked the timing.

[SVG223]

This could be SO many things its hard to find a place to start, especially on a 76. Need a lot more information here.

It could be cooling air flow related, but it could also be related to the tune of the engine or overall engine condition.

I think its worth noting though that the gauge you are looking at is showing your oil temps which are not always the best indicator of if your engine is killing itself or not (im always more concerned with head temps) especially given the vagueness of that particular gauge setup. It may not even be an actual problem unless this is a noticeable change from where it was previously running.

FYI your engine is the only one I have ever seen in 25+ years of 914s that has an intact grommet on the thermostat cable, so I have to ask, has this engine ever been out of the car? If not (and given the fact that im looking at a small leaf in your fan, I would venture to guess that you could have a lot of crud in your engine fins/oil cooler.

The engine seems stock to me, not sure if it has been rebuilt. Odometer has 58k I'm guessing 158k. I took off the smog pump.
The change I noticed when it got hot was a drop in idle speed and it didn't seem to run as well.
Crud in the engine fins/oil cooler sounds possible.

[Superhawk996]

Location?

Ambient temperature?

Speed driven, what gear, what engine RPMs?

20 minutes total or 20 minutes at highway speed & load before temp went up?

Are air injection tubes capped off after smog pump removal?

Any pinging / detonation sounds under load?

Do you know what oil temp sensor part number is being used with this gauge?

All cooling tin and engine seals in place? Any big holes due to missing J pipes?

AC added with hacked up engine shelf and tin on passenger side leaking in hot air?

Going to need more information . . .

Do you have access to boreoscope to inspect inside tin?

[JamesM]

This could be SO many things its hard to find a place to start, especially on a 76. Need a lot more information here.

It could be cooling air flow related, but it could also be related to the tune of the engine or overall engine condition.

I think its worth noting though that the gauge you are looking at is showing your oil temps which are not always the best indicator of if your engine is killing itself or not (im always more concerned with head temps) especially given the vagueness of that particular gauge setup. It may not even be an actual problem unless this is a noticeable change from where it was previously running.

FYI your engine is the only one I have ever seen in 25+ years of 914s that has an intact grommet on the thermostat cable, so I have to ask, has this engine ever been out of the car? If not (and given the fact that im looking at a small leaf in your fan, I would venture to guess that you could have a lot of crud in your engine fins/oil cooler.

The engine seems stock to me, not sure if it has been rebuilt. Odometer has 58k I'm guessing 158k. I took off the smog pump.
The change I noticed when it got hot was a drop in idle speed and it didn't seem to run as well.
Crud in the engine fins/oil cooler sounds possible.

I noticed the belt was missing for the smog pump, if you are not running it you should probably consider removing the pully assembly for it as well as the bearing in them tends to seize up. Also FYI haven't seen one of those that wasn't totally trashed as
well.

Right now I honestly wouldn't be surprised if it actually was a 58k mile car. I would love to see pictures of the rest of it.

While we are on the subject of missing bits, minor issue but the tab that holds down the cooling flap rod is also missing.

[JamesM]

My gut (and my eyes with limited pictures) are telling me the cooling tin has never been off of that engine.

If it is otherwise running good I dont think i would mess with anything else until I pulled the motor and cleaned it out.

[wonkipop]

This could be SO many things its hard to find a place to start, especially on a 76. Need a lot more information here.

It could be cooling air flow related, but it could also be related to the tune of the engine or overall engine condition.

I think its worth noting though that the gauge you are looking at is showing your oil temps which are not always the best indicator of if your engine is killing itself or not (im always more concerned with head temps) especially given the vagueness of that particular gauge setup. It may not even be an actual problem unless this is a noticeable change from where it was previously running.

FYI your engine is the only one I have ever seen in 25+ years of 914s that has an intact grommet on the thermostat cable, so I have to ask, has this engine ever been out of the car? If not (and given the fact that im looking at a small leaf in your fan, I would venture to guess that you could have a lot of crud in your engine fins/oil cooler.

i got one of those them there grommets on my engine if you want to come to australia to look at it. plenty of beers down here and the govt. has opened the doors to the hermit kingdom (IMG:style_emoticons/default/beer.gif)

sounds like a good tip @JamesM re whats under the tin and on the fins since you guys on the top of the world seem to suffer from mice nest problems? (IMG:style_emoticons/default/sad.gif)

only other question i would have for @SVG223 .
what speed on the highway and what revs.
you are not lugging the engine are you?
re the heater hose - the 75 and 76 that ran that second hose did seem to have a little fixture that bolted on to the fan casting and clipped it in position. kind of like a pipe stand off fitting that kept it from falling in over the fan inlet gap. but having said that those impeller fans are pretty efficient and can suck air in from any openings and there would be plenty available to get the volume of air in.

[76-914]

As James said that is the oil temp. Porsche actually changed the gauge markings at one point because it alarmed owners. I've got a '76 and it has always read just as yours shows. Well for the past 13 years anyway. Get a head temp gage if your concerned about engine temps. (IMG:style_emoticons/default/beerchug.gif)

[emerygt350]

The other symptoms point to something out of the ordinary. I would check your plugs for lean conditions, check that timing, look for detritus in the cooling fins. What does your oil look like? If it is low it heats up real quick too.

And buy yourself a cht gauge. Dakota digital makes a nice one and you can install it without cutting your heads up.

[Superhawk996]

Here's the weekly posting of oil temperature gauge vs. calibration vs. which temperature sender.

For reference:


Take note that if someone has replaced the temp sensor with the 120 C / 150 C sender on the 74' (late) gauge that the OP has, the oil temperature can be around 210-220F (great oil temperature) and the gauge will look like its running very hot but there is no concern what so ever.

More concerning if the 200 C (OEM original) sender is in place but still not crazy (300F +).

[Superhawk996]

The other symptoms point to something out of the ordinary. I would check your plugs for lean conditions, check that timing, look for detritus in the cooling fins. What does your oil look like? If it is low it heats up real quick too.

And buy yourself a cht gauge. Dakota digital makes a nice one and you can install it without cutting your heads up.

(IMG:style_emoticons/default/agree.gif)

I don't like the fact that idle was so low. Makes you wonder if a vacuum leak develops when hot and then starts running lean.

Per previous posts . . . too much speculation not enough facts and information to do any real diagnostics. (IMG:style_emoticons/default/sad.gif)

[JamesM]

i got one of those them there grommets on my engine if you want to come to australia to look at it. plenty of beers down here and the govt. has opened the doors to the hermit kingdom (IMG:style_emoticons/default/beer.gif)

sounds like a good tip @JamesM re whats under the tin and on the fins since you guys on the top of the world seem to suffer from mice nest problems? (IMG:style_emoticons/default/sad.gif)

Indeed, we are lacking in enormous mouse eating spiders to help keep the population in check.

May take you up on that beer sometime though, I could use a change of scenery.

[mgphoto]

My 914 overheats on the highway. I had concerns about the air flap, but I think the thermostat has broken and it stays in the open position. I thought something might be clogging the fan but it looks clear. I wonder about the heater air hose that goes over the motor. It could be blocking some air possibly. I may try to tie it out of the way. After exiting the highway and stopping at a stopsign the idle was extremely low, I was surprised it was still running. I turned the engine off for a while and it ran better after it cooled down. Any ideas would be appreciated.

Does the engine have a catalytic converter? Clogged converter will create back pressure causing overheating. ‘76 my in California had them.

[emerygt350]

Good call. Never even thought about that.

[SVG223]

Location?
Arkansas
Ambient temperature?
80f
Speed driven, what gear, what engine RPMs?
5th 75mph
20 minutes total or 20 minutes at highway speed & load before temp went up?
20 min highway speed.
Are air injection tubes capped off after smog pump removal?
Wrapped it with electrical tape, where the hose connected.
Any pinging / detonation sounds under load?
Didn't hear any pinging.
Do you know what oil temp sensor part number is being used with this gauge?
No.
All cooling tin and engine seals in place? Any big holes due to missing J pipes?
As far as I know everything is intact.
AC added with hacked up engine shelf and tin on passenger side leaking in hot air?
No AC added. No AC at all.
Going to need more information . . .

Do you have access to boreoscope to inspect inside tin?
I don't have a borescope yet.

[Superhawk996]

Based on info above I'm more convinced that something isn't right. You should be able to run those speeds, at those ambient conditions all day long without issue.

First thing I would do is verify the part number on the oil temp sender. It's free and easy to do. This at least gets us to a baseline where we know about what temp you're oil really is.

I'm not suggesting that is the problem but it is one of symptoms that got your attention.

Next, I'd get a cheap boreoscope, Amazon, iphone app, whatever. They are pretty cheap.

Make sure you don't have the oil cooler plugged with debris or one of these situations (all 3 came from my own tear down core engines -- 3 of 3 had what would be fatal blockages if you tried to run like this):






Blocked oil coolers are amazingly common on these older cars and there isn't an easy way to clean them as annual maintenance. The rodent problems are very real for vehicles stored a good part of the year. Likewise, mice can build one of these nests very quickly - just a matter of a few days.

Next up: Verify timing and make sure you're not running with too much advance.

We haven't talked about what you're running carbs or fuel injection. Either way, you need to verify that the fuel system isn't running lean. This can be as basic as reading the spark plugs.

As previously mentioned by others a cylinder head temp gauge on Cylinder #3 is a real good thing to have since head temperatures lead oil temperatures by a wide time margin. By the time you see the oil temp going up, the heads have been hot for a long while.

[SVG223]

This could be SO many things its hard to find a place to start, especially on a 76. Need a lot more information here.

It could be cooling air flow related, but it could also be related to the tune of the engine or overall engine condition.

I think its worth noting though that the gauge you are looking at is showing your oil temps which are not always the best indicator of if your engine is killing itself or not (im always more concerned with head temps) especially given the vagueness of that particular gauge setup. It may not even be an actual problem unless this is a noticeable change from where it was previously running.

FYI your engine is the only one I have ever seen in 25+ years of 914s that has an intact grommet on the thermostat cable, so I have to ask, has this engine ever been out of the car? If not (and given the fact that im looking at a small leaf in your fan, I would venture to guess that you could have a lot of crud in your engine fins/oil cooler.

The engine seems stock to me, not sure if it has been rebuilt. Odometer has 58k I'm guessing 158k. I took off the smog pump.
The change I noticed when it got hot was a drop in idle speed and it didn't seem to run as well.
Crud in the engine fins/oil cooler sounds possible.

I noticed the belt was missing for the smog pump, if you are not running it you should probably consider removing the pully assembly for it as well as the bearing in them tends to seize up. Also FYI haven't seen one of those that wasn't totally trashed as
well.
Yes sounds like a good idea. I didn't realize that until I took the picture.
Right now I honestly wouldn't be surprised if it actually was a 58k mile car. I would love to see pictures of the rest of it.
There's a little wear on second gear synchro and a few other things that make me think it couldn't be that low of mileage.
Here is a link to the dealership that I bought the car from they have a bunch of pictures of it. https://www.driversource.com/vehicles/1385/1976-porsche-914
While we are on the subject of missing bits, minor issue but the tab that holds down the cooling flap rod is also missing.
Thanks I didn't know anything was missing I will have to look that part up.