Another cap problem mystery

Having spent most of my own life as a mechanic I wll try to describe the symptoms as accurately as possible without embelishing. The past 30 years or so I have been a heavy duty truck mechanic, no automotive.

  Leaving the Bonneville Salt Flats a couple of weeks ago headed to Los Angeles, about a 700 mile drive. Roughtly 200 miles into the trip I stopped to fuel up and noticed a faint odor from under the hood, smelled like a hot engine but not really pronounced. Temp had been running at normal, outside ambient temps about 90 degrees. I went to open the hood and the cable broke. With some reservations I decided to head out without checking. My next fuel stop was 130 miles away with no service inbetween. 70 miles out my check engine light came on, red light  alt/temp. Temp guage was reading normal at this time so I shut down the engine and decided to hitch a ride into town and call triple aaa. A good amount of smoke was comming out from under the hood along with a distinct hot engine smell, the smell you get when the thiings on your engine that don't burn off at normal temps are now burning off. Temp gage was still reading below the 1/2 way mark just where it always reads. 
    I didn't see anything dripping or spraying from under the car so I assumed I probably froze up an idler pulley and through a belt. Had car towed into a shop and the next morning mechanic said he found nothing wrong, all fluid levels were up, all belts tight etc.  

    To go back a bit when the tow truck driver was picking up the car his lights let me see a thin trail of what appeared to be light oil for as far as I could see going right under my car about to be towed. The oil had no apparent smell. The only smell I am not really familiar with is synthetic oil which I do run in my car. I assumed it was engine oil because it didn't fit anything else. The shop mechanic the next morning said he felt someone else left the train and just by coincedence I followed the identical path. I am sure it was my trail.

   Anyway nothing was found wrong and I made the remaining 500 miles without incident. About a week later I noticed that same faint hot smell after about a 20 mile drive. I decided to push it a bit and see if I could figure out what was wrong. No problem materialized. 

  My only thoughts are at this point is that the car is getting hot without it showing on my guage, or my guage just stops where it stops for some reason and won't read anymore. The thermostat is the only thing I can think of that might be responsible but I am just not sure. I didn't run it long enough with the light on to register a code so no help there. Any theories??

I was thinking on the weekend I may unplug the fan and let it heat up a bit just to see if the temp guage actually registers.

If the check engine light came on my first thought would be what is the code?
Next is the alt light. How is the charging system? If it looks good get it hot turn on a bunch of loads (lights, AC, fan etc) and measure both DC and AC voltage. Above idle DC souls be 13.5-14.5V. AC should measure less than 0.4V.
Keeps us posted.

Year? Make? Model? Mileage?

If by chance you were driving am 80 Fiat Spider, I would say the radiator overflow blew steam, dislodging the coil-to-distributor lead, causing loss of spark, till I noticed it and reconnected it, thus running normal again. This being caused by a beer stop at 7-11 and leaving the car running.

Did I nail it?

Needs better title.

2003 mits montero sport, 110,000 mi. at 100,000 miles I replaced all pulleys, belts, hoses, timing belt or chain, thermostat, waterpump and complete service and tune up. Besides the light comming on the only symptom was the smell of a hot engine. The car never missed a beat.

I have had it on a few short trips (30 miles or so) with everything turned on with no issues. I kind of suspect a sticking thermostat but the guage is reading normal temps. I guess first step would be to verify the guage operation.

Not an 80 Fiat? I got nothin’…


Good luck. Rick will sort you out.

Rick, the alt/temp light are one light. The light was not on long enough to register. I pulled over as soon as it came on. I believe it has to be on for over a certain amount of time to record a code as it does on trucks.

Sorry about the title I can’t edit the spelling.

Check your power steering fluid. It could be leaking and dripping on the exhaust pipes or manifold.

Same can go for the transmission.

Also check the radiator fluid level with the engine cold. Pull off the radiator cap and check it there. The reservoir can be full; however, the radiator actually low.

Checked all the above, my reservoir for some reason has always run empty. There does seem to be a slight trans leak but fluid levels are full.

So it wasn’t the actual check engine light, but a combo alt/oil pressure light that came on? If so that one won’t store a code. Have you checked the electrical system like I described?

Are we talking the coolant reservoir is always empty? :eek:
Why? Where is it going? There has to be a leak either external or internal. Have you pressure tested the system? Have you done a block check? (If doing it with the fluid, make sure you have fresh fluid)
I get nervous when someone tells me the coolant reservoir is always empty. Also burning coolant smells kind of sweet and could be the smell you are describing.

Rick I bought the car 1 year old and for the first couple of years filled the reservoir about once a month. I don’t see any leaks but the radiator has always remained brim full. When the car is hot I have a small amount in the reservoir which goes right back into the radiator when cool. I stopped filling it several years ago.

I plan to check the other things you suggested sunday or monday. The burning smell has me puzzled. It only happens rarely and for no apparent reason or particular driving situation. I came over Baker grade in 100 plus temps and showed no problems. The more I think about it everything seems to point to an intermittent sticking thermostat ( which is brand new) and a defective temp gage. Temp gage will be easy to verify. Thermostat not so easy but I would rather catch it in the act than just change and hope for the best so I can feel some confidence in the car again. I hate to sell it like this and I don’t want to take it on anymore trips till I figure it out.

The best way to describe the burning smell is like this. Say an engine runs at 190 degrees and no more consistently. All the residue that will cook off at 190 cooks off as it is driven. Suddenly for the first time the car heats up to 210 degrees. All the residue that didn’t cook off at 190 is now cooking off at 210. For the most part the engine is clean but if you run your finger over it your finger will come back dirty, this is the stuff that starts to smoke when hot.

Firstly, I’m still somewhat confused by the “check engine light” thing. Did that actually come on, or is it something like a “check gauges light” that just came on at the same time as the temp/alt light?

This is maybe a bit of an out there suggestion, but did anyone check the differentials? Gear oil would match the description of the stuff you’re leaking and if it somehow puked out the front differential vent, it could very easily get on something hot in the engine bay. As I recall, later model Monteros have some sort of ridiculous Rube Goldberg 4 wheel drive system, so I won’t speculate on what *exactly *might have happened, but if there were some sort of intermittent issue with the front differential or transfer case that could explain the fluid leakage and smell, but probably not the alt/temp light.