View Full Version : Coolant temps in LT1 drop as rpm increases??

01-19-06, 11:11 PM
Ok, this is one that I thought a TSB covered, but my car doesn't seem to matter.

The 94 LT1's have a coolant line from the surge tank to the radiator. I have heard the 95's do not. The TSB is to plug the line on the 94's to block it, as it is believed that when the LT1 is at higher rpm's (my thoughts are 3000+ rpm) the coolant temp drops. Scott Mueller said his 94 did it (he installed GM 3.42's) and the TSB fixed his in drive, as he saw it happen often.

Put the car in diagnostics, and go to pointer 24. Drive up to legal speed limit (65 mph somehwere legal) and maintain speed (cruise control), monitoring coolant temp (note I have 3.42's, 2.56 or 2.93 geared cars may need to be going a little faster, hard to say, guys with 3.73's maybe can do it at lesser speeds, or will see it drop temp faster). Once stable, ~85C, drop to 3rd gear. My temp will drop (over 5 min or so) down to 57C. And it to around 65C within 1-2 minutes. Plugging the line as per the TSB did not change anything. Return to OD and temps return to 85C in about 1-2 min. Drop back to D and it starts the fall in temp again.

Does anyone else see this? Or do I have a unique problem? A friend of mine noted that being I have a HD towing package, this might be a good thing when towing a heavy load. May be...

01-20-06, 12:40 AM
I would say it's possible better circulation and more airflow can cause the drop in temp.?

higher waterpump rpms along with more air through radiator would probably be more efficient at a certain speed

Same as say if you were at 5000 rpm it wouldnt be as efficient or 700 rpm would also be inefficient.

01-20-06, 12:50 AM
I currently have my mech fan removed (note no difference in fuel economy still, this is my longer term (cold weather) test, no significant change) so I don't have any airflow there. The electric fan is off. so only ram air through the rad is present.

The thermostat (which is only 11 months old, but does have 30K on it) should control it and maintain it. It strikes me that the coolant that is cooled in the radiator is finding a new way around the thermostat. The theory in the TSB is the little bypass to the top of the radiator was the problem, but as I have seen, not on mine.

I can't see where it might bypass at. Maybe inside waterpump housing?b