Truck heating up

[suladas]

Started happening on monday, even with the below zero temps truck is running warm and will hit 190F like nothing. Coolant is not flowing at all from what I can tell. Upper rad hose is ice cold at rad, lower hose is hot. Am I right to assume it's thermostat, plugged rad, or water pump?

My thought was pull thermostat check it, if that's not it pull rad hoses and see if I get flow through rad? Other then that i'm not sure how to go about checking water pump? Or if those two other things check out good if it even could be anything else?

A few months ago I swapped the coolant from that old green stuff to new red. I flushed it with water twice and ran it, and the water was nice and clean so I figured I did a decent job. No idea if that's in anyway related to my issue now.

 

[92U 3406]

If you're going far enough to inspect the thermostat I'd just replace it.

 

[Former Wrench]

If you're going far enough to inspect the thermostat I'd just replace it.

Agree 100%.

 

[old-iron-habit]

A executive from Stant that I was chatting with at a trade show told me that it is tough to get more than three years out of a stat with the bio friendly antifreezes of today. Fortunately, most of the time they stick open.

 

[Truck Shop]

Hopefully the stat housing retaining bolts will come loose, those can stick shut.

 

[heymccall]

I'm a little slow here.
I can't find the brand of truck, model, or engine type on this post.

 

[Truck Shop]

I'm a little slow here.
I can't find the brand of truck, model, or engine type on this post.

B model Cat--IIRC Western Star.

 

[Truck Shop]

Best test is to leave stat out and see how cool it runs on a short trip, should be hard to hit 130* without
a stat in this weather.

 

[suladas]

B model Cat--IIRC Western Star.

Yes sorry 92 Western Star with Cat 3406B.

 

[suladas]

Best test is to leave stat out and see how cool it runs on a short trip, should be hard to hit 130* without
a stat in this weather.

That makes total sense, will do that, thanks.

 

[suladas]

So got the thermostat out, seems fine. Got a new one and the gaskets. Now i'm wondering, should I still put it back together without thermostat and run it to test, or should I dig into the water pump? I can open the old one no problem, I highly doubt there was anything wrong with it. Since I already have the alternator moved it's not many more bolts to get the water pump cover off now.

 

[Truck Shop]

Get a pot of water on the stove to almost boiling, put a piece of wire around old stat and submerge to
see if it opens. You would have to remove manifold from pump to oil cooler and remove pump as a whole
then remove rear impeller cover to check shape of pump. IIRC.

 

[Delmer]

If the thermostat opened at all, then the upper hose would be hot just from the hot water rising. Checking the thermostat in hot water and finding it won't open will give you the confidence to replace it, without testing the engine without a thermostat.

 

[Coaldust]

3406B’s always have bad water pumps and we’ve kicked that dead horse many times on here. I’m certain you will find a bad impeller. If you are lucky, it probably has one of those original fiber impellers known for slipping on the shaft.

Paid my mortgage and fed my kids changing 3406B water pumps and broken exhaust manifold bolts.

 

[Mobiltech]

If you are checking water pump make sure you also look at the inlet face of the engine oil cooler. That is where all the gunk in the system is filtered out before it gets to the block. I have seen many plugged there. You will have the inlet pipe off the cooler if you are checking the water pump impeller.

 

[Mobiltech]

3406B’s always have bad water pumps and we’ve kicked that dead horse many times on here. I’m certain you will find a bad impeller. If you are lucky, it probably has one of those original fiber impellers known for slipping on the shaft.

Paid my mortgage and fed my kids changing 3406B water pumps and broken exhaust manifold bolts.

I have always wondered why Cat hasn’t improved their manifold studs on 3406 - c15 and 3306 engines. Definitely a weak spot.

 

[Delmer]

Was your heater working when the top radiator hose was cold? If the heater is working, then the water pump is working, right?

 

[suladas]

Confirmed thermostat works fine with water, I put new one in for comparison also and it's exactly the same in the amount in opens. Yes the heater works great. I am going to pull lower rad hose and flush rad and just make sure it's not plugged before I tear into water pump.

 

[Former Wrench]

It could that the lower hose is bad. Perhaps the inside of the hose has come loose and when the pump is pulling coolant, the hose is collapsing, creating a flow blockage.

 

[suladas]

Water pump is out and seems fine. I held one side and can’t get other to turn, there is no play at all. From the looks of it and the way most bolts were bad, I suspect it was replaced at some point. Water flows out the rad fine, I mean there is some crap in there but I can’t see where it’s my issue? Only thing I can think of is maybe the thermostat was stuck and me opening it with a screwdriver broke it free?