I have a 1991 Silverado with a 305 ci. engine and I can't get it over 150 degrees. I changed the thermostat 2 times and tried removing the fan.I also blocked off the radiator, all did not help. I by passed the heater thinking that might be doing it, but no good.My gauge is correct because I also put a test thermometer in the Rad. and both read the same. Any help will be appreciated.

 

I had a 90 that was like that and nothing had any affect on it. I replaced the lower heater hose and the troublesome connector that scews into the intake with a hose barb and it works great. Dont ask me to explain it.

 

Thank you for the idea. If it works , I owe you big time!!!

 

I'm having the same problem...did it work for you?

 

No it did not, going to try more things ---will get back on it.

 

does the heater blow hot? have you tested the gauge?? comparing a thermometer in the radiator to the dash gauge isn't accurate

heater and radiator hoses feel hot/warm to the touch?

 

What about the temp sending unit? Have you tried that? I would try a mechanical temp gauge to see if it reads the same.

 

I have replaced the heater core. I bought a Stant thermostat. I flushed the system twice. I replaced both sensors. The coolant itself is just not hot. I believe the gauges are telling the truth. The heat is warm, at best. This all started when I replaced the intake manifold gasket. I have a friend who's truck did the exact same thing when he did the same job. There was an extra little pin hope in the new gasket and we think that's allowing enough coolant through to keep it cooler

 

Did the intake gasket have the two end ports blocked off with a tin cover? It should have.

 

It did. But I noticed in the slot where the coolant flows to the heater core, there was an extra hole about the size of a skittle that wasn't on the original.