Overheating then cooling issue

I'm experiencing a problem with my 89 Sierra 5.7L TBI.

Here's what I've replaced within the last 30 days: Radiator Radiator Cap Upper & Lower Hose Thermostat Water pump Coolant Temp Sensor on intake manifold

There are no leaks. Or at least none that I can find.

Here's the problem: The truck heats up to operating temp, and then continues up to 260F. The "check gauges" light comes on and then about 30 seconds later, the temperature drops to 210 (normal)...and then operates just fine. Occasionally, I will hear gurgling in the heater core, but not consistently. Sometimes it happens when the engine is hot, sometimes when it is just warming up and sometimes it doesn't happen at all. The reservior remains full.

The oil was just changed about 2 weeks ago and is dark. I can't find any traces of coolant in it.

Does anyone have any suggestions as to the cause? Could the guage itself be malfunctioning? Any help would be appreciated.

Reply to
Vincent
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Sounds like maybe the fan clutch is taking a dump on you. How full is your rad, and how much liquid is in the overflow? If it's underfull, you'll get air in the system and it'll gurggle.

I'm currently having a similar problem without the gurgling sound. My temp gets up to about 215-225 and then the fan clutch kicks in and it cools off immediately. I think part of my problem is that the wrench that installed the rad for me used 100% coolant. Not a good idea.

Sam

Reply to
GaWd

appreciated.

Could be the t stat sticking then letting go when it gets up to 260. If its the fan clutch you should hear it kick in when it gets to 260, it will sound like an airplane when the engine is at high rpm. The fan clutch sould kick in at about 220 and not 260... It is possible the gauge isnt working right or the sendor. Did you change the sensor(for the computer) or the sender(for the gauge) ? Did it do this same thing before the new t stat?

Reply to
Scott M

I don't think its the t-stat. I had the same problem with the old one and the new one. I changed the sender on the intake manifold for the gauge and still experiencing the same problem. I did NOT change anything for the computer.

I'm getting the fan clutch replaced tonight. If that doesn't work, then I'll try testing it for a day or two with out a thermostat. The Texas heat should help the engine warm up.

Reply to
Vincent

Water Wetter works. Good stuff. I added a single bottle, and saw a drop of nearly 10F on my normal operating temperature. I have no idea how it does that, but it is impressive. One of the few "works as advertised" products in the automotive world.

Big Chris

Reply to
Big Chris

I always thought that the sender on the intake manifold was for the computer, and the one in the cylinder head was for the gauge itself, could be wrong though.

Daniel Mobley snipped-for-privacy@bellsouth.net

Reply to
Daniel Mobley

That's how my 4.3 is setup...

Reply to
Mike Levy

I would be very interested in hearing what you find out on this issue. I have a 96 GMC Sub, with a 5.7 TBI, and had the same symptoms you're experiencing-which ultimately led to a blown head gasket, somewhere between

5th and 7th cylinder. I replaced the engine, due to other complications that came later, but I am still seeing the full overflow, gurgling in the heater core, and low level in the radiator. The dealership has not been able to determine the cause but it appears that for some reason the system is not drawing fluid back from the overflow. I've replaced the hose, radiator cap, and even attempted to get all the air out of the system by flushing on an incline with the rear heater open and flowing. No luck. A warped head, loose bolt, or bad head gasket perhaps--allowing the system to push minute amounts of air in the cooling system?? Don't know.

Keep an eye on the fluid level in the radiator, remove the cap and force the overflow fluid back in when needed, so you don't end up like I did with a blown gasket due to excessive over-heating.

Good luck,

Reply to
M

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