Platypus1

Drove into Dallas today, engine temp was stable ont he way up. On the way back however, she began fluctuating in temperature. I got home and checked fluids and they were fine. MY catalytic converter tested bad the other day, can this cause the engine to get hot due to the back pressure?
Thermostat is new.

suprathepeg

To a certain degree yes, how much it will effect it I don't know.

84sr5yoty

Yes. Plugged cats will even turn the exhaust manifold(s) cherry red.

trythis

My chevy s-10's cat was burnt and blocked and it caused so much back pressure it broke the exhaust manifolds bolts off the back cylinders. I had no idea it was bad until I was replacing my clutch and chunks fell out of the cat. when I removed it. You would notice serious power loss if your cat was blocked though, have you thought of chaning your thermostat? THat can cause many other problems, and inconsistant temperature doesnt sound like a back pressure issue.

Platypus1

Thermostat was changed about 1.5 mos ago. My truck has been acting very bizarre the passed week. For example, tonight I was driving home and the engine idle would jump up and down, like I was goosing the throttle in the 700 to 1000 rpm range. when i gave it gas, it would sputter a little, then go. The tach would show the same small fluctuations as the engine accelerated. Power would go from normal to sluggish at intermittent times. As mentioned above, engine heat fluctuated today, yet radiator was full. Another wierd thing, radiator hoses have had to be tightened because pressure seems to be above normal in the system.

Oil is fine.

Fuel filter is brand new.

HAd engine tested a month ago and everything was fine. Engine only has about 5000 miles on it.

No idea where to look other than maybe that cat, or maybe my radiator is going bad.

Elvota

When you had the "engine tested", did they check compression? You may have the beginings of a head gasket issue. Coolant doesn't always effect the oil, sometimes exhaust enters the cooling system. This might explain the high pressure on the radiator lines. Might cause the fluxuation in temp as well.

4x4Lamm

Sounds like the morning I found out my headgasket was blew, sorry Platypus.


Lamm

Platypus1

That is my greatest fear, however when I took the truck in a month ago a compression test was performed and results were fine. Hopefuly it is something else much less serious!!

4x4Lamm

Well mine went from fine to WTH is wrong in about 5 miles, so it can happen quick.

Lamm