bgetz

I'll try to explain without getting too long.
2004 Chev. SSR 5.3 LS-1
This vehicle has a closed loop coolant system with a 15# Pressure cap.

It all started as an overheat in at a traffic light 3 weeks ago. Got it out on the open highway and it cooled down quickly.
Checked fan by turning on air conditioning while running. Fan runs.
At this point I'm thinking this is a thermostat problem. Top hose hot, bottom hose cool, heater hoses hot.

Custom tune, lowered fan temps, had done 2 years ago with no problems.

Issue at hand is the high speed fan comes on at about 190-200 degrees.
Now keep in mind that the thermostat is 186 degree (OE temp) and "blends" coolant to keep the engine at that relative temperature. That's what it's supposed to do. It's a new thermostat and I have tested it in hot water.

It's driving me crazy and this is one of those problems you can easily throw allot of money at and get no where.

Someone said that the fuse box in this year was corroding so I took it apart. Found no corrosion, VERY careful with reassembly to keep it clean.

I have already replaced: high speed fan sensor, water temp sensor in the head, coolant tank cap 15 psi, 186 degree G.M. thermostat

JetMech442

iTrader: (1)

Hi Bgetz,
As I understand the post, you are concerned about overheating at idle(resolved at highway speeds) and also the fan coming on at 190-200...?

For the first one, you've done a lot of the troubleshooting already-checked Tstat, pressure cap, temp sensor..etc. The only issues left I can think of that would attribute are low WP flow, or inadequate radiator air flow.

The only thing I can think of that would change during service life would be an obstruction in the system that would reduce flow(clogged-dirty radiator?).

The radiator air side(external fins) may also be dirty. To check either of these, you could use a thermal gun on the top and bottom radiator hose when engine is hot, and then compare to soemone with a similar engine/setup.

Hope this helps for ideas. LEt me know if I misunderstood your problem.

Ferocity02

iTrader: (60)

The coolant temp sensor is in the cylinder head, it will see a higher temp then the thermostat, hence the fans will turn on before the thermostat fully opens when warming up if the two temp settings are relatively close. Also you can't trust the gauge in the cluster, you need a scan tool to truly see what temp the fans are turning on at. The temp of the thermostat is only of significance when air is moving through the radiator. If no air is moving through the radiator then it will overheat no matter what.

An air bubble can also cause this. This has happened to me a couple times after completely draining the system for engine work. The temps got up to 230+, fans came on at 190, but the radiator hose was still cool. The bubble somehow prevented the hot coolant from getting to the thermostat. Some engine revving a squeezing freed the bubble and the temps dropped quickly as the thermostat opened.

bgetz

Thank You for your replies.... On the intake of the LS-1 there is a place to "burp" the air from the engine.
Tried that
Squeezed the lower radiator hose like a teenage boy on a prom date with his large bosomed girlfriend. no good
It will sit idling and will not overheat because the fan is on HIGH speed, I'm guessing this is due to the thermostat being a mixing a "mixing valve" of sorts.
Once over 35mph the computer shuts the fan off as far as my hearing can tell.
This vehicle never ever acted like this until it really got hot about a month ago. I mean it was nearly pegged
BUT
I have not ruled out the gauge stepper motor yet as I don't know how to check it.

Kawabuggy

iTrader: (1)

I don't know if it was on this post, or another, but someone mentioned filling their cooling system the same way I do.. Remove upper radiator hose and hold it up as high as you can and then remove cap from coolant reservoir.. Fill through the upper radiator hose until the reservoir is full and this usually gets rid of all air in the system. If you suspect it's air flow ACROSS/THROUGH the radiator... Again... I would be trying a different radiator. Try a factory single row and see how it does.. You have nothing to lose at this point except a little time. I have 4 LS style radiators here from 99 Silverados.. I buy them every time I'm at the pull a part as I put them into most swaps I do.. They have all the connections for LS engines, and I can make brackets to mount them easily enough. They will also cool ANY LS engine I've ever built without issue. If you are in, or close to, Houston.. Come by my shop.. I'll give you one for free to try.

RonSSNova

iTrader: (3)

Well, you suckered for an 8 y/o post
😊

I fill my rad that way, with the front steam vents loosened. Works well