Heater flow/temp issue?

[1990Z71Swede]

A plastic cutting board and a throttle spring off a moped.... What gives?

You must be registered for see images attach

Tadaaaa! Mode actuator lever spares

You must be registered for see images attach

It was almost impossile to install them, but I finally managed. Atleast now I can get ALL of the not so hot air onto the windshield

 

[1990Z71Swede]

Oookey, so I might have found the problem. Winter is long gone, and by the end of it the cabin heat was sorta ok but intermittently sorta not. I was starting to think I had some loose crud floating around, sometimes partially blocking the heater port in the manifold.
So I had planned to do a proper flush, with the QD removed, sometime during the summer.

Today the truck stalled on my daughter (unrelated to the heater issue) and I had to do some well overdue basic maintainance. When checking coolant level. I found this:

You must be registered for see images attach

....And what I beleive was causing the backfire, black smoke, unhappy cat smell and stalling. The loose ignition wire on #7 was probably not helping either. Replaced rotor and cap with NOS ACdelco parts. Ran fine after that, but the slight miss every now and then at idle is telling me she still wants plugs.

You must be registered for see images attach

Empty boxes and the worn out cap and rotor.

You must be registered for see images attach

 

[termite]

Oookey, so I might have found the problem. Winter is long gone, and by the end of it the cabin heat was sorta ok but intermittently sorta not. I was starting to think I had some loose crud floating around, sometimes partially blocking the heater port in the manifold.
So I had planned to do a proper flush, with the QD removed, sometime during the summer.

Today the truck stalled on my daughter (unrelated to the heater issue) and I had to do some well overdue basic maintainance. When checking coolant level. I found this:

You must be registered for see images attach

....And what I beleive was causing the backfire, black smoke, unhappy cat smell and stalling. The loose ignition wire on #7 was probably not helping either. Replaced rotor and cap with NOS ACdelco parts. Ran fine after that, but the slight miss every now and then at idle is telling me she still wants plugs.

You must be registered for see images attach

Empty boxes and the worn out cap and rotor.

You must be registered for see images attach

Is that grass in the cap spring?

 

[1990Z71Swede]

Is that grass in the cap spring?

Yes sir. I bet the PO have had to scoop water or maybe even snow out of a ditch at some point. Possibly related to the replaced thermostat that I found installed Backwards.

 

[termite]

I found a few really small pebbles in my suburban cooling system upon flushing it to get the rear heater working properly. Nothing is too surprising. Least they could have done was use a rag to "filter" the solids out if it's necessary to dip water from unclean sources.

 

[FourEightZero]

Hey guys,

I apologize for just jumping into another thread, but this is relevant.

Is the check valve on this t-stat going to close as soon as the air is purged from underneath? It's just a free-floating ball inside that valve housing.

 

[Schurkey]

Is the check valve on this t-stat going to close as soon as the air is purged from underneath? It's just a free-floating ball inside that valve housing.

I've never seen one like that before.

Wild Guess: Allows air to bubble out, but also opens when the water pump spins and produces pressure in the engine. The only time it's shut is when the engine is not running, and has no air in the water jackets.

Seems to be an expensive way to vent air compared to the stamped, tiny hole in a Robertshaw thermostat.

 

[FourEightZero]

I've never seen one like that before.

Wild Guess: Allows air to bubble out, but also opens when the water pump spins and produces pressure in the engine. The only time it's shut is when the engine is not running, and has no air in the water jackets.

Seems to be an expensive way to vent air compared to the stamped, tiny hole in a Robertshaw thermostat.

Thanks again Schurkey.

It's a smaller hole than the 1/8" hole I drilled in the one currently in the truck. (I know.. I've learned since).

Did an early morning datalog today. Ambient temp was 64°F and coolant temp wasn't going over ~145°F. I've been doing midday runs up until now and engine was getting up to full temp.

Now I'm worried about not being able to heat up my cab this winter as well as oil contaminants not being able to be cooked off.

What do you suggest? Just use the regular stat?

 

[Schurkey]

If that one doesn't allow proper engine temp, it's gotta come out. What temp is it rated for?

 

[pressureangle]

You must be registered for see images attach

Soo, With European studded Snow tyres on, and the wonky power steering now fixed. This is an AMAZING ride in the Winter. Every bit as fun as the old Audi Quattro I used to have years ago, just with a LOT more Cowbell
Except... Cabin Heat.
It is not cutting it. Apparently when it works it is supposedly very efficient, not so much on this truck though.

So far I have flushed the heater and backflushed the QD on the intake going to the heater, including the hoses to and from the heater. There were no signs of blockage anywhere really and the water coming out of the heater was clean.

What I have noticed so far is engine temp is not stable and fluctuating between maye 60-90 degrees centigrade. But it is difficult to say really becase the scale on the gauge is a bit weird. I'm going to start with replacing the Thermostat with a 195F from Gates.

Also, the hose going into the heater is only hot...ish I can hold it but I'm not sure my wife could . The same hose on the 2008 Suburban is somewhat hotter, hot enough that I can't hold it very long.

The hose coming out of the heater in the truck is maybe luke warm, on the Burb it is significantly hotter.

The blend door actuator seems to be working fine and the fact that the heater return water is not hot points to a flow problem and not an actuator issue.

I've topped up the coolant and tried to bleed the system with the truck at an incline to rule out air pockets which did not change anything.

So what should be my next move? Maybe the new thermostat will fix everything? (I doubt it will but I think it is part of the problem at least)

Is a clapped out water pump a likely cause on these engines? (1990 350TBI) It does not leak or show any other signs of mechanical distress though.

You mention high capacity cooling (radiator). Past the point of your upside down thermostat (hue hue) my 5.7 with big radiator takes a long time to get the entire system stabilized in very cold weather- the t-stat opens, floods the engine with cold water from the radiator, snaps shut, opens again...rinse and repeat for 20 minutes if not at speed. You can put a bit more heat in it with some ignition timing, if you haven't already. Also it's common in our North to cover half (or all, sometimes) of the radiator with a piece of cardboard, especially the diesel guys.