I smell coolant and my mpgs are down.

[bucksandbirds]

but there are no visible leaks and my mechanic did a pressure test with no leaks found. The smell seems to be coming from the thermostat housing area.
The coolant in the overflow tank will be down a very tiny amount over a few week period, hardly noticeable.

It also sounds like my thermostat is kicking open every few minutes or more often. I can here what I would associate as the tell tale noise of a thermostat trying to open. (clicking followed by a mechanical cycling sound) Geez that sounds vague. I'm sorry.


Not sure that it's associated, but my mpg's have also gone down from about 18/19 to 15/16.


I have done the associated things for a tuneup. coilpack, plugs, wires, fuel filter.

Am I missing a vacuum leak somewhere?

I'm getting tired of pouring money into the truck, but realistically I am not getting rid of it as I would just do a newish motor once this one fails.

The truck is a sohc 4.0 with just a tick over 160k.
Runs strong, with some noise on initial startup.

 

[Joe Dirt]

I would try by replacing the thermostat if you think it has issues. That could also explain the MPG drop.

 

[vroomzoomboom]

It also sounds like my thermostat is kicking open every few minutes or more often. I can here what I would associate as the tell tale noise of a thermostat trying to open. (clicking followed by a mechanical cycling sound) Geez that sounds vague. I'm sorry.

that i would have to think is your a/c compressor cycling. when it does that, is the heater control on defrost? as for mpg, it might go down some depending on how cold it is as well. i know mine drops about 3 or so mpg in the winter.

 

[bucksandbirds]

that i would have to think is your a/c compressor cycling. when it does that, is the heater control on defrost? as for mpg, it might go down some depending on how cold it is as well. i know mine drops about 3 or so mpg in the winter.

It doesnt matter if the hvac is on or off. The cycling noise is still there.

The temp drop seems logical I suppose, but I didn't expect it to be so drastic.

 

[bucksandbirds]

I would try by replacing the thermostat if you think it has issues. That could also explain the MPG drop.

I dont know that it does?
The temp gauge is never out of whack, I just narrowed down the coolant smell eminating from that immediate area.

On occasion, the oil pressure seems to be a tick over halfway... These are all probably completely unrelated issues.

 

[ssp.interceptor]

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[MidnightRebel07]

Look around the motor and under the motor for white or greenish crusty stuff. When the leak is so minor the coolant evaporates before it makes it to the ground or even able to run down and be visible.

I had this problem on my wifes '97 Mounty V8 AWD, found out it was the thermostat housing was barely leaking and the upper lower rad hose (bypass) clamp was loose and leaking, just barely though.

 

[eazyasone23]

Lower intake gasket

 

[ssp.interceptor]

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[ChrisTM]

You could pull the thermostat and test it in water on your stove. If it passes put it back in and re-seal it. Rule out two problems (thermostat and seal around it) without spending any money and only using about an hour.