Thermostat Opening Late?

[97C1500TJ]

I’m new to the TBI motors as my other 400 is a Vortec. I don’t think it’s normal but want to verify in case it is. The temp gauge on my truck from a cold start will climb to 210 before the thermostat opens. The stat is rated for 195. 210 isn’t overly hot but I think there could be a faulty thermostat or an air pocket. Any other ideas? Once it opens, it drops back down to 195.

 

[PlayingWithTBI]

The temp gauge on my truck from a cold start will climb to 210 before the thermostat opens. The stat is rated for 195. 210 isn’t overly hot but I think there could be a faulty thermostat or an air pocket.

Nah, mine does pretty much the same thing only the gauge shows it going to ~212° then leveling off at ~206°. The ECM is seeing ~194° with a high of ~198°. IMO the sensor in the head isn't getting full flow of coolant (plus it's in between combustion chambers) like the one next to the T-Stat housing. I'm running aluminum heads, a Tuff Stuff 1675A high flow aluminum water pump, a Flow Cooler 330-195 high volume T-Stat, and an oversize 3 row aluminum radiator - I'm not worried

 

[97C1500TJ]

That’s good to know. Another thing I’ve noticed as of today is that my new radiator cap is already leaking. Parts quality must’ve taken an even more significant nose dive this past year.

 

[Nad_Yvalhosert]

Thermostats arent fully open until 23° after their designed temp rating. That means a 195° isnt allowing full coolant flow until 218°.
The later, more modern fuel injected engines run at high temps to reduce NOx.
210° is OK.
220° is... livable.

 

[97C1500TJ]

So after a few days of driving, all temperatures stay normal. My only concern is that my coolant is boiling in my upper hose. I filled the rad up and let it idle for half an hour with the front end lifted up on my lift to elevate the radiator so it’s not air in the system. No bubbling is coming up from the coolant so I don’t think it’s a head gasket. I believe it may be a blockage somewhere in the coolant passages. Any ideas?

 

[GoToGuy]

What gives you the indication, not idea but what actually tells you it's boiling? You understand the principle of pressurized cooling system? Did you do any testing? Your thermostat is functioning normally.

 

[97C1500TJ]

What gives you the indication, not idea but what actually tells you it's boiling? You understand the principle of pressurized cooling system? Did you do any testing? Your thermostat is functioning normally.

I can feel the upper hose after driving and it is bubbling/boiling inside. My 97 does not do this nor do any of the Hondas I work on. I feel that I have a restricted cooling system. Bear in mind that this is my first TBI engine so some things are a little different than I’m used to.

 

[GoToGuy]

This is occurs after stop and shutdown? If yes, that is normal as cooling fluid is no longer moving transferring the heat , or providing cooling from the radiator. Therefore the now static fluid is absorbing the residual engine heat and appears to be boiling. This condition is normal, water temp may rise, stay at shutdown or start dropping quickly. Each is unique for type, use, weather conditions, age so on.

 

[GoToGuy]

Have you checked your radiator cap? Both seals intact no cracks splits, pliable not rock hard? Pressure checked the cap? If you had a restriction most likely you would have an overheat not running normal temps.

 

[97C1500TJ]

The previous cap was leaking and was replaced yesterday with the same issue minus the leaking. The previous cap was also only 3 weeks old.