2.8 cooling prob's- thermostat relocation

[BIGBLOCK44RANGER]

recently bought my 4th rbv. A 85 pu w/2.8 The temp guage read a little over half way when I drove it home, no big deal. I noticed a leaking water pump. So in changing it I realized the radiater had sevral gashes in it so I replaced it, and while I wuz at it got new hoses and a thermostat(its in the lower hose housing). problem is that when i drive it over bout 20 mins the temp guage reads toward hot. But the heater blows cold air, I know the duct door is mooving and the heater worked when I bought the truck. I've searched here sum and read about the air lock prob with the 2.8. I dought this is my prob cuz i filled the engine before filling the radiator and warmed it up before i topped it off. I've checked the coolant level sevral times, and its always full. Would changing the thermostat to the top help? do u remove the lower t-stat completely, and is there any other mods to this? like hoses or hose routing? just weird to have a temp guage on hot and no heater but full of antifreeze. been messin with this for a couple months now with no luck changin anything. any help or ideas are appreciated-

 

[r1hatman]

Check and see if someone has put a thermostat up top too like mine was. They had two and it was doing the same thing yours is doing. So I took the top one out and put in a 160 thermo on bottom and it's been fine ever since.

 

[kimcrwbr1]

I put a tee in the heater hose going to the heater and top it off from there just get a $5 flush kit and hook it up to the hose. Add your coolant to the radiator then statr the engine and when the engine starts getting warm add water through the tee slowly until it starts coming out the radiator. Once you get the heater working good It will finish bleeding itself just top it off cold and keep coolant in the reservor. I got lucky at the bone yard and found a 2 piece t-stat housing that goes on the intake manifold. I removed the lower stat and plugged the 3/4 inch nipple off the intake manifold for the bypass and put a 1 inch hose from the rear bypass housing to the upper t-stat housing and a 195 stat in it. It never went above half way this summer on the guage and the heater works real good. You will notice when the heater is working the temp will stabilize.

 

[BIGBLOCK44RANGER]

I actually have a bII 2.8 for parts. I checked it last night and it has a different upper thermostat housing. but the bottom looks the same on both but the bII has a hose going to the stat housing, and on my pu it goes to the intake. Is this the two peice upper stat kind maybe?? could I use the hose and housing on the on the pu to move the t-stat to the top? Oh, and Ive already had the upper off of the pu and its just a housing, no t-stat. It would be nice if those parts would interchange-

 

[Mudhound]

You can swap back/forth between the 2 styles on the 84-85 2.8 My 84 BII actually PREFERS to have the T-stat in the bottom fiting, with the top open. Never had any troubles with that causing the overheating that you are describing. You also have to watch the parts houses, as sometimes they give you a T-stat that goes in the wrong direction, and will not open because of this. I use the Robert Shaw "balanced" one with no troubles, once again. $9, but it beats blowing the motor.

 

[strvger]

my '83 2.8 uses a 3 row radiator while your '85 is a single row, according to the lmc catalog. your radiator is 1/2 inch wider, same height, but the single row is only 1" deep. my 3 row is 2" deep. if you're still having cooling problems after doing the thermostat work, you might want to see if you could fit the earlier model 3 row rad in your truck.
just a thought.

 

[BIGBLOCK44RANGER]

I checked a few things again last night. after making sure the coolant wuz full at the rad and engine(loosened the fitting on the upper hose adapter) I drove it about 30 mins ending with the same results. 1 heater hose hot the other cold, the upper rad hose hot and the lower cold. It didnt gain any pressure so I took the cap off and of coarse the coolant isnt flowing, its almost like the things not gettin hot enough to open the t-stat, or bypassing it through the hose on the back- I'm gunna try to relocate the t-stat to the top and see if it makes a difference i guess. The thermostat I put in it did not have a hole and it looked sorta cheezy but its what they had. I wudn mind the guage sayin the motors a lil hot, if I had a heater-lol. maybe just a junky t-stat, its happened b4

 

[kimcrwbr1]

I actually have a bII 2.8 for parts. I checked it last night and it has a different upper thermostat housing. but the bottom looks the same on both but the bII has a hose going to the stat housing, and on my pu it goes to the intake. Is this the two peice upper stat kind maybe?? could I use the hose and housing on the on the pu to move the t-stat to the top? Oh, and Ive already had the upper off of the pu and its just a housing, no t-stat. It would be nice if those parts would interchange-

That sounds like the one I am using . I put a plug in the nipple coming off the intake for the bypass and you can get a 1" hose to fit the housing. Just take the stat out of the lower housing and put it in the upper one. I had to tweak the radiator hose to fit and for bleeding you can drill a small hole in the thermostat and put it on the top when you install it. The stock bypass hose goes from 3/4 to 1" and using the upper t-stat housing you need a 1" bent hose. I actually just cut the old bypass a few inches from the intake and shoved a spark plug in and clamped it it still holds water. Keep the 195 t-stat in there for the computer it will still run alot cooler and reset the computer by disconnecting the batt for a half hour. A pic would be nice but the stat is verticle in the housing right and the bleed hole dont need to be very big say 1/16 to 3/32.

 

[kimcrwbr1]

I kept going thru water pumps they always leaked out the shaft seal since I changed the housing I have not had an ussue. You can take the housing up to the part store and match up gaskets for it might be the easyest.

 

[kimcrwbr1]

I guarantee you if you put a radiator flush kit in the heater hose and fill the system from there your heater will work. It will fill the block and heater core once you add al,l the coolant hook it up to a hose with a valve on the end start the engine and slowly add water until it runs out the fill hole on the radiator. once the heater is working you got it dicked.

 

[BIGBLOCK44RANGER]

air in the system is not my prob, Im very confident that the engine is completely full of coolant- It really acts like the t-stat is just not opening- my question is will the upper t-stat style housing bolt on the other intake or will it have to change intakes. If it wont I'll just machine the upper housing for a random t-stat of the rite size, and drill a bleed hole in it-

 

[Big Jim M]

Guys I'm not familiar with the top or bottom hot coolant exiting from the engine...
BUT? Wouldn't you have to have a reverse flow coolant pump to change the flow AROUND?
Big Jim

 

[kimcrwbr1]

No the housing will fit just fine and it work the same as a regular cooling system. You can change the intake over but it is not necessary you just need to plug the bypass on the intake and use the bypass on the housing like I said. As the thermostat opens it closes the bypass also to increase flow thru the radiator. You dont need no special pump just a 1 inch hose for the bypass from the t-stat housing to the lower rear cap that circulates the coolant thru the engine and the heater core if your heater is not working it is because of air trapped I am certain of it. Been there done that I cant explain it but put the tee in there and prove me wrong. my theory is air circulates thru the water pump thru the heater core not allowing the thermostat to open. The first time I ran into that problem the guy at the bone yard told me to boil the thermostat and put it in real quick while it was still open I laughed in his face. I am 100 % sure if you pull the heater hose off the intake manifold and force some water in thru the heater core where it runs out somewhere your heater will start working and the temp will stabilize.

 

[kimcrwbr1]

Guys I'm not familiar with the top or bottom hot coolant exiting from the engine...
BUT? Wouldn't you have to have a reverse flow coolant pump to change the flow AROUND?
Big Jim

I can`t explain it either but the system still pulls coolant from the lower hose and out the upper hose but the hot coolant gets mixed with the cool as it goes into the engine at the thermostat. Some goofy german engineering thing. I never measured the temp of the coolant coming out of the engine but with a 195 stat it must have been upward of 220 degrees. using the same sender my guage never goes up past half in hot weather with the the stat on the intake going out the engine.

 

[r1hatman]

I always use a fail safe thermo, if it goes bad it will lock in the open position.