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.
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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?

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.

Good eye on the grommet.

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.

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.

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?

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.

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.

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

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?

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.

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.

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.

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

For reference:
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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 +).

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.

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.

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

Good call. Never even thought about that.

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):
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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.

Also wanted to ask which front spoiler or valance you are using and about ride height

you need some air to flow under the car
temps will go up if the car is too low or if the spoiler is too close to the ground.

brant

@SVG223

hey thats a good looking car you got hold of.
i looked at the photo gallery in the link you posted.
seems to be all there, very original and in nice condition.

without wishing to add to lists of what could be wrong -
@emerygt350 suggestion of a blocked cat isn't silly and worth checking.
i can believe that car just might be a 50+K miler and if so might still have a 45 year old cat on the exhaust. i couldn't see if so from the dealer ad photo gallery.

good luck with it and follow the D jet guys advice on this forum.
i own an L jet so wouldn't have a clue when it comes to these.

but don't forget to keep the revs at 2800-3000 out on the highway for aircooled peace of mind.

EDIT - ps checking out that photo gallery your heater hose looks fine and shouldn't be blocking fan air flow. its all beautifully stock in there and in amazing condition. and i got into the full gallery at high res - its still got a cat on the exhaust.
it kind of looks original.

we do have mice down here. introduced species (unlike the cute native marsupial mice) and it is a pest when they get into plague proportions out in farm country. happens every 10 years. but they tend to eat everything (like wiring) but for some reason don't do the nest building thing. seem to prefer holes in the ground. maybe something to do with it being hot? not super cold like USA? dunno. but we definitely don't seem to have that unbelievable nest building crazed species that you guys suffer through. i can't believe some of the photos i have seen of what they get up to in your neck of the woods.

its the deadly snakes that get them and keep the numbers down in normal times.
the spiders are more interested in attacking people.

I will check the plugs. The oil looks clean.
I think the mechanic that just did the valves checked the timing and went over the car and said it was all good. He may not have driven it far enough for it to get hot.

@emerygt350 do you have a part no handy for the Dakota gauge you mentioned? Thx.

probably not easy to check exhaust back pressure on 914 of that vintage.
modern cars you plug into 02 sensor in front of cat.
someone on this site might know how to do it if sensor plug in not available.
your mechanic may even know how to.

a couple of weeks ago one of our circle brought his wife's audi into the workshop.
it wouldn't make power properly past idle and it was running slightly hot.
turned out the cat had spat a piece from inside which is like a ring or pipe connector and this had turned sideways in the outlet pipe and was blocking it.
cat was not that old either, but it was an aftermarket cat.

you might be able to get the cat off to inspect it visually.
likely to be a pain in the a with stubborn nuts.
your mechanic could do it.

1- ODYR/SLX-11-1--BLUE-K - Cylinder Head Temperature
Color: Blue
Bezel/Trim/Finish: Black
@ $124.95 ($124.95)
1- SEN-11-8 - Cylinder Head Temperature Sender Length 18' for 14mm spark plugs @ $26.95 ($26.95)

you don't need 18' feet.

https://www.dakotadigital.com/

Whatever the mileage, that thing looks to have been very well taken care of.


As mentioned a plugged CAT can cause issues for sure, but that would probably cause you issues everywhere, not just oil temps on the freeway. Still probably worth pulling it given you have disabled the smog pump as well. My bet is still on gunk in the oil cooler/engine fins being the primary issue. Your cooling tin/screws/fan housing looks way to pristine and original, I dont think they have ever been removed so most likely have 50 years of crud in there.


When you do sort it out though (or maybe even before) get rid of those KYB shocks and replace them with literally anything else. It will feel like a whole new (and much nicer) car.

Remove the cat, there is an after market bypass pipe that can replace it.

Thanks for these pictures they give me an idea of what could be happening. Stock D Jetronic. A head temp gauge would be nice, ideally, it would be a vdo gauge in place of the clock in the center console.

true - you don't need 18' but remember that you can't just cut/shorten that lead.

Don't know if anyone else has mentioned this, but make sure the fan belt is tight. If it's slipping, you won't get the air flow over the heads that you need to cool them down.

That's a Porsche/diff type thing. Our fans are direct mount. Belt only runs the alternator.

i would start by confirming the oil temp in the sump with a mainly by design style oil temp dip sticks for 914-4's - mainly by design was purchased by ron at precision matters - i only see 356 oil temp dip sticks on his site - there are also gene berg type iv oil dip stick sensors as well - i would start systematically with the accuracy of the oil temp gauge before chasing other issues - i have a thermostatically controlled external oil cooler, custom mount, w/fan, after years of experimenting with verified oil temps - hope this helps

http://www.914world.com/bbs2/index.php?showtopic=334157

Thank you.

Delete/Replace the cat converter and clean the oil cooler. The cooler will be a bit of a chore. Purchase new cooler seals (I would get 2 sets. They keep.) before you start the process.

I think the ignition timing has been retarded by a bunch. I just turned the distributor counter-clockwise enough to increase the idle by 1000rpm and it ran better, so far no overheating but it's not summer yet. I need to get a timing light. I tried to get it to ping but it didn't so I need the light. It is running well so far.

You are playing with fire.

Detonation kills engines so fast you would hardly believe it. The ability to hear detonation on an an air cooled engine is impaired by the valve clatter and fan noise.

Get a timing light on it. Stop guessing

Thanks, will do that. I didn't expect the timing to be off, purchasing it from a dealer that had done a tune-up on it. I had my doubts about it because of the vacuum hoses being misrouted. The engine runs much better now and doesn't overheat so far. That overheating was keeping me from driving it. I didn't know ignition timing had that much effect on engine temperature.

Too much or too little advance timing will raise temps.
Yes, put a light on it. Under no load it will be hard to make ping. It will certainly ping as soon as you put load on it once the engine is over-advanced.

Remove the crap from the engine that you are not using.
If you don't use the smog pump - pull it off the engine. Cap the ports. Those go directly into your combustion chambers. Don't trust duct tape! IIRC, an M8 nut cap works fine on the port.

And, yeah, get an inspection camera / borescope and look in your tins for debris especially your oil cooler. I'm sure its caked over with grime.

Zach

I hear no pinging under load I may have guessed correctly, but the light will come in tomorrow so I can check. I pulled all of the smog crap off and getting some vacuum
caps tomorrow. I got a borescope camera and almost everything was covered with grease. I pumped a gallon of diesel fuel through the holes in the sheet metal, but I didn't get it all out.

Did you check and clean the oil cooler? Or is that what you were talking about?

Zach

Yes the cylinder fins and the oil cooler. I had to have help with the cooling flaps to get them in the right position to flush the oil cooler with diesel. I suppose the engine would have to come out to do a thorough clean. I'm still hoping that the new ignition timing will allow me to drive it this summer.

Just clearing out all the crap on top of the oil cooler may be enough to bring temps into check.

Zach

Has a "high temperature" ever been confirmed with any means other than the factory oil temp gauge? even a hand held infrared