All my weirdness:, Temp problem? Gauge problem? Wiring problem? Options

[Mike Sanford]

This is long, but I'm trying to get all my car's issues in.

I have a 74 1.8, l-jet. Owned for about a year and a half. Aftermarket oil cooler with an electric fan on it in the rear. Petronix ignitor and MSD box installed since I bought the car. A few unsorted problems I'm trying to work out, don't know if they're all related.

Voltmeter and temperature gauge in what I think the PO said was an aftermarket center console.

I live in the middle of a very hot town, many of my trips are less than 2 miles, lots of stoplights. Longest trip I've made in this car is 14 miles.

In October my ECU went out. Replaced with another used ECU. The following problems have happened with both ECU's, and before and after installing the Petronix and the MSD.

Sometimes, and this will happen for weeks on end, the temperature gauge will climb to the redline within the space of a 4 mile drive. Doesn't seem dependent on ambient temperature. My solution so far when the car has been acting like this, take the Honda if I'm going more than 4 miles.

Sometimes, and this has occurred for periods of up to two months, the temperature gauge will seem normal.

Sometimes, during periods of time when the car is reading hot, and this has only happened four or five times, the temperature gauge will spike to the redline within a half mile of driving. If I turn off the key, and turn it back on, it will return to what seems like a normal reading.

Sometimes, also during periods of time when the car is reading hot, the temperature gauge will bounce up and down if my turn signal is on.

During the periods of time when the car is not reading hot, I've had trouble with what felt like fuel starvation randomly, stalling or almost stalling.

Idle is pretty random, no matter what I set the idle at. 800 rpm one stop light, 1700 the next.

Car just entered another phase of "reading" hot this weekend. Went out and bought an infrared thermometer. Drove it long enough to intentionally bring the gauge into the red. Got readings of 280-290F at the cylinder head, aiming as close as I could to the spark plugs. Readings of 180F off of the tuna can. From what I can gather, this is a fairly inaccurate way to gather temperatures. But these also don't seem like problematic temperatures. I need to drive the car to emissions this week, which is farther than my 4 mile range.

I'll wait for the wisdom of the World.

[timothy_nd28]

I don't care for the infrared thermometers. Many of them have a fixed emissivity ratio that doesn't fair well with shiny objects. Consider buying a oil thermometer that inserts into the dip stick tube.

This should be the first thing done. If you do confirm high temps with the stick thermometer, you should inspect the engines thermostatic bellows. Then the oil cooler (make sure you have no chipmunk/scorpion nest) in the airflow pathway.

Consider temporarily removing the aux air valve and capping the branch and plenum ports. See if your idle is more consistent. IF not, start hunting for vacuum leaks

[Mike Sanford]

Are you in town yet? How is the work going? Its awesome convertible weather now, I'm just scared to take mine very far.

Tried to find a dipstick thermometer specifically for the 914 and couldn't. Mainely Custom no longer has one on their website, emailed them and asked if they were still made, and heard no reply.

I'm under the impression that to really inspect the bellows and the cooler, I'm going to have to drop the engine.

[timothy_nd28]

I'm in Tucson this Friday. Engine dropping isn't necessary for the bellows inspection, it's fairly accessible from underneath the car.

I question your existing sender and gauge. eBay sells a oil temp gauge/sender kit for under 50 bucks. It may be worth buying this if you can't source a oil temp dip stick.

[TheCabinetmaker]

Sounds like the wire from the sender is intermitantly shorting.

[Mike Sanford]

Tim- I'll look into the ebay kit. My search so far had just led me into things that were more in the $150-$250 range.

I can see a short happening when the gauge pegs over within a minute or two, and then returns. But those other drives when it climbs up over 4 miles seem different.

The little reading I've done made it sound like no one on the site believed the infrared was accurate. But the numbers I was getting with it also didn't seem worrisome. Do you think it could be considered a ball park number, in which case I'd keep driving, or completely unreliable?

[timothy_nd28]

When they first came out, I purchased one thinking it would be an awesome tool in the HVAC business. After using this tool only a handful times, it proved way inaccurate. This tool currently sits in my kids toy bin. They like to use it with our cat, as the cat chases the laser beam.

[Mike Sanford]

Just about to boil some water, and point it at the outside of the shiny pan.
Should give me an idea of how far off it is.

[Mike Sanford]

Here's my boiling water experiment results:

In a pot much more reflective than anything on my car, the infrared bounced all over the place. Numbers rapidly cycling like 142, 220, 187, 150, 210. The high numbers were fairly close to the surface of the water, which read a steady 209.

I'm going to order the oil temp gauge, and for the time being "trust" the highest readings I get off of the infrared more than I trust the gauge in the car.

[bdstone914]

Inspect the wire from the sender. It probably has cracks in the insulation and shorting out which will give high temp readings.
Everything you say indicates an electrical problem not a real temp problem. Also look at the ceramic part of the sender for cracks. You will have to remove the cover to see it. You may then need to replace the two 6mm copper crush washers and paper gasket under the cover.
Bruce

[Black22]

Won't the Mainley 912 version work? It's a type 4 and I believe the dipstick tube is located in the same location as ours...I believe.

[Mike Sanford]

Drove the 9 miles to get the car emmissioned, passed, drove the 9 miles back. 181F off the tuna can after all of this, 190F on the case itself near the can. The infrared gun doesn't "bounce" numbers around on the car like it did on my shiny water pot.

Probably all I get to play with the car today, gotta work sometime.

[Java2570]

The Mainely dipstick for the 912 is actually a 356 dipstick and also works on older 912s. It's not for the Type 4... I know because I tried it and had to return it. They don't make the 914 version anymore and I may have gotten the last unit that was sitting around. One of the salesmen happened to have it when I returned the 912/356 dipstick.

[timothy_nd28]

You mind posting the emission results? I will be doing the exact same thing next Monday.

[76-914]

To all using IR thermometers. Read the directions that come with it. There should be some mention of the relationship between distance and mass. This effected the accuracy of mine. I found that I could not accurately measure the temp on a 1" line from 25'.

[Mike Sanford]

This year they only did a idle test. Last year they tested it both idling and driving, not sure why there is a difference.

Hydrocarbons PPM 85 out of a 400 limit.
CO% 4.42 with a 5.5 limit.

You're going to have that car driving by Monday?

[timothy_nd28]

That's the plan. (IMG:style_emoticons/default/blink.gif)