1984 Bronco II - 2 Thermostats??? FIXED/RESOLVED Overheating Issue

[cyclejohn]

I used the search feature on the forum to try and find the answer to my question, and to not bother anyone on the forum, but, after reading through pages of threads and post I still haven't found an answer to my question.

So here goes: The 1984 Bronco II that I bought about a month ago started running hot (actually blowing coolant and steam out the rad cap into the coolant reservoir) within 6 or 7 miles of the place where I bought it. The radiator and reservoir both had the correct level prior to driving away. I told my daughter to just park it and get in the car with me and we would go home and I would send a tow to pick it up. I just hate that I drove 100 miles to buy it.

Anyway, picked up and delivered to my house the next day. My daughter explained to me how the B II felt during the few miles that it actually drove. I am finding so many mechanical problems that weren't visually apparent when I checked it out the day prior to purchase. No big deal because I can fix what I have found by robbing parts off of the '84 Bronco II that my daughter totaled in a wreck back in December.

In going through the cooling system to verify good flow and no blockages, I removed the lower radiator hose mount housing on the lower left side of water pump, and it had a 205° thermostat in it, verified it was opening in a pot of water with a temp reading probe in the water. Started opening at 205 and was fully open at 215.
The upper radiator hose mount housing attached to the front top of the intake manifold had a 180° thermostat in it. Verified by the temp probe and pot of water. Starts opening at 180 and fully open by 190°.

My question: In all of the threads and post I have read here, I have never seen the word 'dual thermostats', '2 thermostats', or 'thermostats', only the singular use of the word thermostat. The '84 that I am robbing parts off of had a single 180° thermostat in the bottom radiator hose mount housing and the temps on it always ran exactly where it needed to be.
Is it OK to just run one thermostat in one of the hose housings??? If yes, which one would be the better location to do it???

Thanks for any insight into this.,

John

 

[Shran]

Yes... some had dual thermostats. My '85 Ranger does and it says right on the core support that there are two thermostats and there's a special procedure for draining the coolant or something like that. I'm not quite sure why they did that, I suspect it had something to do with the computer controlled carb, emissions, etc.

I guess if I was to run just one I would be tempted to run the upper one.

Curious why your truck was overheating though? Did you find the cause of that?

 

[cyclejohn]

1) I guess if I was to run just one I would be tempted to run the upper one.

2) Curious why your truck was overheating though? Did you find the cause of that?

Hey Shran,

Thanks for the info and quick response.

1) That would certainly make it more convenient if I ever needed to replace the thermostat again.

2) What I have found so far since the flatbed tow truck transported the truck to my house:
I jacked it up and put it on stands all the way around. The right front brake caliper was frozen in the 'out' position and the pads rubbed so hard against the rotor that it cracked the rotor completely through in 2 places. The left front caliper was frozen in the out position also and the pads were rubbing heavily against the rotor but not as bad as the right side. The calipers, rotors, and pads, on the totaled Bronco were good so I robbed them. Both sides of the rear brakes, the shoes were partially disintegrated and the wheel cylinders were weeping, another rob job there.
I was going over things in the engine bay and when I grabbed the distributor cap it easily twisted in both directions. The hold-down bolt was finger turning loose. I'm sure ignition timing was playing into the overheating. The brakes being lock up weighed into it heavily also. I haven't pulled the EGR valve yet so I don't know what I will find there, time will tell. The totaled Bronco intake has a block off plate where the EGR goes.
I wasn't really concerned about the strong gas smell and slight black smoke coming from the exhaust at the time of purchase because I was already planning on robbing the Duraspark and Holley conversion off of the totaled Bronco and swapping it over. That Duraspark and Holley conversion totally transformed the wrecked (in it's un-wrecked state of being) Bronco to be a viable mode of transportation. So I had high hopes for this replacement Bronco.

Shran, have you ever verified the thermostats opening degrees at the 2 locations in your truck??? I don't understand why one of the thermostats is a 180 (upper) and the other thermostat (lower) is a 205???

Again, Thanks

John

 

[fastpakr]

Fascinating - I don't remember ever reading about a second thermostat being installed on the top before. The one on the bottom was the stock location for my '84.

 

[fastpakr]

Yes... some had dual thermostats. My '85 Ranger does and it says right on the core support that there are two thermostats and there's a special procedure for draining the coolant or something like that. I'm not quite sure why they did that, I suspect it had something to do with the computer controlled carb, emissions, etc.

Can you take a picture of the dual thermostat sticker? I'm really curious to see that and try to get my head wrapped around it.

 

[Shran]

Hey Shran,
Shran, have you ever verified the thermostats opening degrees at the 2 locations in your truck??? I don't understand why one of the thermostats is a 180 (upper) and the other thermostat (lower) is a 205???

I have not, I really haven't done much with the truck beyond pushing it around my yard. Hopefully I will have time to dig into it this winter - I picked it up as a project truck for my kid, it needs floor pans and has a dead A4LD (but I did get it running!)

Can you take a picture of the dual thermostat sticker? I'm really curious to see that and try to get my head wrapped around it.

Sure thing. I had heard of dual thermostats on 2.8 trucks before but haven't seen one in person. The 83s, 84s and 85s I had in the past didn't stick around long enough for me to actually look, but none of them had that sticker either IIRC.

 

[Shran]

@fastpakr I may have been mistaken. This was the sticker on my '85, I am not sure why I remembered it saying something about dual thermostats.

 

[fastpakr]

Thanks. So that takes me back to assuming all 2.8 RBV's had bottom mounted thermostat, and anything on top should be removed.

 

[bobbywalter]

Yes...single t stat....lower. and make damn sure the block is full.

 

[4x4prepper]

re: dual thermostats

Single or dual, I drill a 1/8" hole in the thermostats. I have a 2.8L from what I assume is a 1974 Pinto - Mustang II has that weird lower housing and weird upper housing. I think I deleted the upper thermostat because I coud never get it to properly seat and seal. I used the Permatex on the lower multiple piece housing and had no problems.

 

[Paulos]

Here's some info on the 2.8 thermostats that I found. The author suggests that it's either one or the other, top or bottom, not both.

 

[cyclejohn]

Hi, John here.

I started a thread on Sept. 15 about my '84 Bronco II having 2 thermostats in it and that the engine was overheating/running hot. I have always liked it best when reading through forums, that if someone post up about a problem, once the problem has been resolved, another post be made telling about the final fix for it. It just seems to be the best way of sharing information for anyone else that comes along and has the same issue.

This is my attempt to do just that.

When I started the other thread I had already started tearing into engine, that's how I found the 2 thermostats. The bottom thermostat was a 205° and the top was a 180°. By the time I finished 'tearing into it' I had removed most everything attached to the engine and most of the wiring harness in the engine bay.

I checked all of the hoses attached to the cooling system and they were clear. Because I was already into it I put all new hoses on. The radiator was brand new from the previous owner but I pulled it anyway and ran the water hose into the top hose mount and flipped it over and ran it into the bottom hose mount. Both ways were clear just the way they should be.

I did not put a thermostat back into the intake manifold thermostat housing. I installed a 180° thermostat in the water inlet housing on the lower left side of the water pump.

I am not sure that the fan shroud that is on it is the one it was born with. It does have 2.8L V6 ONLY molded into the top but there was a 3/4" gap all the way down the left side of the shroud and a 7/8" gap all the way down the right side. I went to LOWES and bought an 8' section of the soft rubbery foam pipe sleeve and cut that to fill in the gaps on both sides of the shroud. The fan clutch was questionable at best (I could reach down with my gloved had and stop the blades with no effort at idle and with RPMs raised a bit) so I put a new one on.

The in-dash temp gauge didn't work when I bought the Bronco so I robbed the temp sending sensor from the totaled BII and installed it and also corrected the fubar wiring going to it. The aftermarket analog readout temp gauge that someone had installed under the dash didn't strike me as being reliable so I don't use it and will probably delete it.

With all that said the top things I did that corrected the overheat issue:

1) Only running 1 thermostat now. A 180° at the lower housing location.

2) Replaced the fan clutch.

3) Sealed the sides of the fan shroud. Pulls much more air through the radiator now.

Now with the in-dash temp gauge working, the temp needle never goes above a smidge below halfway of the gauge. With the engine fully warmed up I removed the radiator cap and stuck my wife's fancy/expensive meat probe (like you use when cooking) in the coolant in the radiator and it never read above 150°. When the meat probe is showing 150° the aftermarket analog gauge mounted under the dash has a reading of 201°.

So, I'm going to stick a fork in this overheating issue, it's done.

John

 

[cyclejohn]

A SHOUT-OUT and 2 thumbs up to Uncle Gump for all the help and guidance he has given to me since I joined this forum.



Thank You,
John