Overheating -- still!

[mejulihn]

I talked with Tom at Pelican Parts regarding an overheating problem with my '76 2.0 that I believe may be related to a lean mixture. The car starts nicely, idles well, takes five or so miles to warm up to normal temp range (180-220). It then keeps climbing slowly to over 250 degrees. Tom theorized that maybe my CHT sensor may need replacing. He indicated that the sensor should tell the EFI to richen the mixture when the temp gets high. If it gets too hot it should shut down the EFI. Does it sound like we are on the right track?

[Joe Bob]

First thing you need to do is put your engine on an exhaust analyzer....check the CO and HC. THEN start from there. You need to know why you are running lean, you will just throw money and parts at a potentially mythical problem...

[This message has been edited by mikez (edited 11-20-1999).]

[JP Noonan]

I agree, you should test things out first, try the D-Jet article on the 914 fan site. The CHT can be tested with an ohms meter, although a new one is only about $12. The sniffer test will tell for sure what is wrong, if it is a A/F mixture problem that gets worse with engine temp. it is most likley the CHT.

Other things to consider. Are all the engine seals in place? Mainly the engine compartment seal, the sparkplug boot seals, the J-tube seals, and also see if you still have the two air directing flaps at the rear of the floorpan. When/if you replace the CHT see if there is a build-up of crap covering the cylinders, pine needles and leaves get sucked up by the fan and cover the cooling fins. Also is the motor covered in dirt, see if a local garage can steam clean it.

All this dirt may not be the problem (especially if the problem happened suddenly) but it isn't helping. A missing seal is, in effect, a hole in your radiator.

[mejulihn]

I have checked the usual suspects: the cooling fan is unobstructed, warm up flaps are operating normally (I did remove the thermostat bellows), all engine tin is in place and openings plugged, cooling fins around the cylinders are clean, and I just finished replacing all the intake system seals.

[Dave at Pelican Parts]

The head temp sensor leans the mixture at higher temps. It is intended for enriching the mixture during engine warm-up, not for preserving the motor if things get hot. AFAIK, there is no "overtemp cutoff" in the 914 except for the driver and the ignition key.

Are you sure that the temps are what you think they are?

How's the timing?

Are you sure the cooling flaps are there, and that the one over the cooler is open? Five miles may be a little short for the engine to warm up with the flaps open all the time. The lever on the cross-shaft should be more or less straight up.

Not sure what else offhand. Perhaps debris under the engine tin? Good luck!

--DD