Total Loss of Engine Temperature

[asorensen]

As I write this I believe I know what the responses will be although I am still hopeful for an easy explanation and fix. Read on.

On a recent trip (approximately 3 hours in) I had my temperature gauge drop to zero (no reading). I believe I caught this fairly quickly but from my understanding this is very bad meaning no coolant to read temperature from. I pulled over immediately and upon inspection realized that my rad cap was cool to the touch and upon opening found the coolant to be low. I had checked the coolant perhaps a month earlier and at that point required no coolant. I did not observe any leaks from under neath and the van was running fine. Because I absolutely needed to carry on (flight to catch) I filled my coolant and carried on for approximately 15 mins at about 80km/hr. I still had no reading on the gauge and the van ran fine for those 15 mins. At the next stop I again checked the rad cap and was able to open it (cool to touch) and again the coolant was low. At this point I was able to stop driving it and have it towed. After 4 days I went back to it. I started fine although had some white smoke which disappeared after the revs where increased and definitely didn't continue through any of the driving I did afterward. The coolant level was fine. My oil did not show any signs of water although it was a bit lower than the level I had started with pre-trip. I removed the under panels and observed for leaks while idling. I then drove the van for 30 mins or so at 50-80km/hr The gauge did not move. No leaks were apparent and the coolant level stayed the same. I did not have the guts to take the van for a longer and faster trip with the gauge still showing nothing and this is were I have left it.

My van has new rad hoses, water pump and thermostat but I haven't changed the rad or cap.

My thoughts range from head gasket to faulty gauge or sensor. Where is the location of the engine temperature sensor?


What are peoples thoughts?

Andy

[Schwa]

Almost sounds like what happened to my 1980 E-100 Van when the thermostat got stuck wide open, it refused to warm up whatsoever... It had a mechanical fan for the radiator, without the heat activated clutch so any heat generated would be stripped away by the rad even when idling. I know my fan clutch is stuck "on" so probably others are too, so it could be a faulty thermostat. It's too bad it's not so easy to access as most engines.

[delicat]

If it was a faulty gauge you're radiator cap should still be hot...

Do you have any heat coming from your heater inside?

The only time I had problem with a head gasket I couldn't get any heat inside and you'd see water in your oil. (or loads of white smoke!)

Wish I could help more but no mechanic by any means.

[dfnder]

I'm thinking with the cooler weather that maybe your thermostat is stuck wide open like has been suggested. Having a cool engine is not great but an overheated one is definately not good. Why would you be so short of coolant - that would be my main query.

Does your engine smell differant than normal? If your engine is running hotter than it normally does you may smell a differance. You may be lucky and it could just be the thermastat, you could always cover the rad partially if you are confident it isn't overheating to see if the temp goes up :)

[EricN]

What do you call "low on coolant"? 1L, 4L, 8L? If you are only adding 1 or 2L then the coolant isnt low enough to cause the problem. If you can take the rad cap off easily without a big burst of steam or pressure, you are not overheating, or getting hot for that matter.
Start the truck, warm it up at idle, even put some cardboard in front of the rad. Keep checking the temps of the upper and lower rad hoses, they will probably be the same (unless the thermostat is working,then they will be very different untill it gets hot and opens). It should warm up. When the hoses are very hot to the touch, remove the cardboard and watch the guage. I am betting you sill see it drop. If the hoses are hot to the touch and there is still no reading, then I would bet on the guage/sender circuit.

[asorensen]

Thank you for the responses. You all are smarter than me! I hadn't thought about the thermostat being stuck open and this sounds like a good option.

The engine seems to be running fine with no real discernible change in performance or smell.

EricN asked:

What do you call "low on coolant"? 1L, 4L, 8L? If you are only adding 1 or 2L then the coolant isnt low enough to cause the problem.

I had to add about 1.5 -2 L of water so from your stand point not enough to cause an issue. There wasn't a huge burst of steam or tons of pressure when I first opened it so I guess this also could be indicating a stuck open thermostat.

I will try to get a reading on the temperature gauge by covering the rad but I won't be able to try it out until Friday.

Thanks again for the help.

Andy

[Jester]

so did you figure it out? was it the thermostat?

[Jester]

p.s.
If you have no obvious hose or rad cracks, or a source of a leak, it could simply be a rad cap issue.
Perhaps it's not holding the proper pressure, and bleeding off the fluid into the overflow prematurely...
Just a thought, but that's where I'd start, just change the cap ($10-12), top up the coolant and see what happens.

[asorensen]

Yes, I did figure out the problem. I meant to have a nice picture as clear example of the problem but my camera card reader bit it. Sorry for the delay. The thermostat was in fact stuck open as the other smart members suggested. The unfortunate thing was I had replaced this when I did the timing belts back in June and this was a new thermostat. The rubber seal had broken free, evidently a faulty part. I ended up testing my old one and then after it tested positive (opened up at approx. 82 degrees) I put the old one back in. Done and done

Andy

[after oil]

nice work andy! good advice i got on another forum when troubleshooting my nissan diesel was, when having cooling problems, start by changing the thermostat and rad cap. its quick and cheap and eliminates them right away from the equation...