radiator overflow question
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Fleet Mechanic
Joined: Jul 2013
Posts: 1,997
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From: NE Ohio
radiator overflow question
I'm trying to figure out my 86. My 79 doesn't seem to have this issue. (both 460's) I actually have a colder stat in the 79 and don't see condensation issues in it at all..
The 86 doesn't overheat, per se. It has a 180 t-stat from best I can tell.
Meaning, my digital temp gauge shows once it hits 180, it will drop in temp for a bit (means it's opening to me)
When it does get around 204 I hear the clutch fan engage and it drops in temp pretty quick than as well.
If it hits 210 and I shut it down, it will fill the overflow tank and overflow it. (this happens above 205 really)
I usually fill the radiator to about an 1" below the cap or till I can't see the "core"
That high seems to overflow it.
I want to stick a 195 t-stat in it but I'm concerned it will overflow all the time than.
I'm dealing with condensation in the engine oil because my trips are too short. I try to let it warm up but it really isn't enough with a 180 stat.
I don't think I have a head gasket leak because oil lvl doesn't increase but it sure seems milkshake looking now that cold weather is here.
Maybe I'm just overfilling it?
The 86 doesn't overheat, per se. It has a 180 t-stat from best I can tell.
Meaning, my digital temp gauge shows once it hits 180, it will drop in temp for a bit (means it's opening to me)
When it does get around 204 I hear the clutch fan engage and it drops in temp pretty quick than as well.
If it hits 210 and I shut it down, it will fill the overflow tank and overflow it. (this happens above 205 really)
I usually fill the radiator to about an 1" below the cap or till I can't see the "core"
That high seems to overflow it.
I want to stick a 195 t-stat in it but I'm concerned it will overflow all the time than.
I'm dealing with condensation in the engine oil because my trips are too short. I try to let it warm up but it really isn't enough with a 180 stat.
I don't think I have a head gasket leak because oil lvl doesn't increase but it sure seems milkshake looking now that cold weather is here.
Maybe I'm just overfilling it?
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
First off the rad should be filled fully as you have the overflow bottle. The 1" below the cap is the rule if you have no overflow bottle.
And it is normal for the engine to push out some coolant once you shut it off as once you shut the engine off the latent heat in the block and heads is no longer being carried by circulating coolant and it will heat up the coolant up resulting in it pushing some coolant out to the overflow bottle. When the engine cools this coolant will then be sucked back into the cooling system from the overflow bottle.
Make sure the overflow hose it at the bottom of the overflow bottle, and it should only be a 1/3- 1/2 full on a cold engine You may have to reposition the hose in the bottle and drain some of the coolant out of it.
And it is normal for the engine to push out some coolant once you shut it off as once you shut the engine off the latent heat in the block and heads is no longer being carried by circulating coolant and it will heat up the coolant up resulting in it pushing some coolant out to the overflow bottle. When the engine cools this coolant will then be sucked back into the cooling system from the overflow bottle.
Make sure the overflow hose it at the bottom of the overflow bottle, and it should only be a 1/3- 1/2 full on a cold engine You may have to reposition the hose in the bottle and drain some of the coolant out of it.
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Joined: Jan 2001
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Likes: 2,763
From: Virginia
Like was mentioned, overflow is normal. You will get more with a lower pound radiator cap. Most of these engines I have seen came with a 13lb cap. If your radiator is iffy, you can run a 7 lbs cap, but you will get more overflow. If you have a brand new radiator, you can run a 16lb cap and have less overflow. But 16lbs is a lot for a older truck with a older heater core and older radiator.
Thread Starter
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Fleet Mechanic
Joined: Jul 2013
Posts: 1,997
Likes: 237
From: NE Ohio
I'm glad you brought up the cap because I didn't even think to look at it. I have no idea what its rated at.
I will check it out.
I figured it was normal to get overflow but if I fill the reservoir up 1/3 of the way, it will overflow from that.
I wouldn't think I'd get overflow from the reservoir at 220 even. But I am at a lower temp. The cap may have something to do with it.
As it stands now, I have to leave it empty, keep it showing the 1st core or I get overflow when the engine gets up in temp but still safe.
(according to my gauges)
I should also take a temp reading to make sure all the gauges are accurate which I haven't done yet, I'm just assuming they are..
Is there supposed to be a cap on the reservoir or is it left open? Mine does not have any cap on it.
I will check it out.
I figured it was normal to get overflow but if I fill the reservoir up 1/3 of the way, it will overflow from that.
I wouldn't think I'd get overflow from the reservoir at 220 even. But I am at a lower temp. The cap may have something to do with it.
As it stands now, I have to leave it empty, keep it showing the 1st core or I get overflow when the engine gets up in temp but still safe.
(according to my gauges)
I should also take a temp reading to make sure all the gauges are accurate which I haven't done yet, I'm just assuming they are..
Is there supposed to be a cap on the reservoir or is it left open? Mine does not have any cap on it.
Moderator
Joined: Jan 2001
Posts: 57,027
Likes: 2,763
From: Virginia
I have never really figured out the overflow reservoirs on these trucks. It's almost like they were designed just to catch the overflow from hitting the ground, but that's it. I have never seen one of these trucks with a nice cap on the reservoir where you can fill it and then cap it off, without rigging something up. They have a "plug" on top of the reservoir, and you pretty much have to dig it out to open it up. And after you ruin the plug you have to rig some other cap on it. There must be a little groove somewhere around the top that lets air in and out, because I have sealed off the hole with a homemade cap and it still works normally.
The old 1980 I had, I broke the whole complete lid off where they glued it, and just took the whole lid off when I needed to fill it, It worked well also to clean it out. On the 1984 Bronco II I have now, someone has removed the plug and has sort of threaded a plastic pipe fitting in the hole to plug it off. My 1989 diesel has an official overflow bottle with a nice removable cap. But it's a later truck. Don't know when they started doing that.
The old 1980 I had, I broke the whole complete lid off where they glued it, and just took the whole lid off when I needed to fill it, It worked well also to clean it out. On the 1984 Bronco II I have now, someone has removed the plug and has sort of threaded a plastic pipe fitting in the hole to plug it off. My 1989 diesel has an official overflow bottle with a nice removable cap. But it's a later truck. Don't know when they started doing that.
Thread Starter
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Fleet Mechanic
Joined: Jul 2013
Posts: 1,997
Likes: 237
From: NE Ohio
I'll see if I can rig something up to seal it up, but first to check on that cap rating.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 790
From: Simi Valley, CA
I'm glad you brought up the cap because I didn't even think to look at it. I have no idea what its rated at.
I will check it out.
I figured it was normal to get overflow but if I fill the reservoir up 1/3 of the way, it will overflow from that.
I wouldn't think I'd get overflow from the reservoir at 220 even. But I am at a lower temp. The cap may have something to do with it.
As it stands now, I have to leave it empty, keep it showing the 1st core or I get overflow when the engine gets up in temp but still safe.
(according to my gauges)
I should also take a temp reading to make sure all the gauges are accurate which I haven't done yet, I'm just assuming they are..
Is there supposed to be a cap on the reservoir
or is it left open? 
Mine does not have any cap on it.
I will check it out.
I figured it was normal to get overflow but if I fill the reservoir up 1/3 of the way, it will overflow from that.
I wouldn't think I'd get overflow from the reservoir at 220 even. But I am at a lower temp. The cap may have something to do with it.
As it stands now, I have to leave it empty, keep it showing the 1st core or I get overflow when the engine gets up in temp but still safe.
(according to my gauges)
I should also take a temp reading to make sure all the gauges are accurate which I haven't done yet, I'm just assuming they are..
Is there supposed to be a cap on the reservoir
or is it left open? Mine does not have any cap on it.Reservoir is the same 1985/86 F150/350 & Bronco with gas engines: E5TZ-17618-A Obsolete ~ No Ford dealer or obsolete parts vendor has any NOS, none on ebay.
The cap may have also been used on 1980/84 F100/350 & Bronco with gas engines, but this reservoir is different than 1985/86.
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Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
I'm glad you brought up the cap because I didn't even think to look at it. I have no idea what its rated at.
I will check it out.
I figured it was normal to get overflow but if I fill the reservoir up 1/3 of the way, it will overflow from that.
I wouldn't think I'd get overflow from the reservoir at 220 even. But I am at a lower temp. The cap may have something to do with it.
As it stands now, I have to leave it empty, keep it showing the 1st core or I get overflow when the engine gets up in temp but still safe.
(according to my gauges)
I should also take a temp reading to make sure all the gauges are accurate which I haven't done yet, I'm just assuming they are..
Is there supposed to be a cap on the reservoir or is it left open? Mine does not have any cap on it.
I will check it out.
I figured it was normal to get overflow but if I fill the reservoir up 1/3 of the way, it will overflow from that.
I wouldn't think I'd get overflow from the reservoir at 220 even. But I am at a lower temp. The cap may have something to do with it.
As it stands now, I have to leave it empty, keep it showing the 1st core or I get overflow when the engine gets up in temp but still safe.
(according to my gauges)
I should also take a temp reading to make sure all the gauges are accurate which I haven't done yet, I'm just assuming they are..
Is there supposed to be a cap on the reservoir or is it left open? Mine does not have any cap on it.
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My saga may be of interest to you. The cooling system seemed to venting early into the overflow reservoir. I had tested the cap and the rest of the system separately, but never together. I finally found a problem at the junction between the radiator neck and the succession of perfectly good caps.
https://www.ford-trucks.com/forums/1...lant-leak.html
https://www.ford-trucks.com/forums/1...lant-leak.html
Moderator
Joined: Jan 2001
Posts: 57,027
Likes: 2,763
From: Virginia
These trucks have a bottle, but like I said it seems to just be a catch can. But it can work as a overflow bottle if you can find a way to fill it manually, and have a recovery cap. Most caps are recovery caps now, back in the day when these trucks were made, not all caps were recovery caps.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
An official "overflow reservoir" has a removable cap. The radiator is filled to the top, and then the reservoir has lines on it for "cold" and "hot". It's an official extension of the radiator system, catching the excess from the radiator, and then putting it back in the radiator, keeping the radiator full to the top. You can't fill the radiator to the top without a reservoir bottle. You must have a air space for expansion in the top of the radiator without a bottle.
These trucks have a bottle, but like I said it seems to just be a catch can. But it can work as an overflow bottle if you can find a way to fill it manually, and have a recovery cap. Most caps are recovery caps now, back in the day when these trucks were made, not all caps were recovery caps.
These trucks have a bottle, but like I said it seems to just be a catch can. But it can work as an overflow bottle if you can find a way to fill it manually, and have a recovery cap. Most caps are recovery caps now, back in the day when these trucks were made, not all caps were recovery caps.
Any catch can that has the hose to the bottom of the container will act as an overflow reservoir. A 2-liter pop bottle will do the job in a pinch. ALL of these trucks had dual seal caps in fact basically ALL vehicles since the late 50's have had dual seal style caps. Just in back in the era the hose was routed down the side of the rad to the ground instead of to a container. Install a catch can on any of these vehicles and it will act as a recovery reservoir. You technically do not even need to fill the bottle up but it speeds the process up. Just doing a rad top up when the engine is cold will eventually fill the container enough to keep the rad full.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
IIRC that is what they had in them originally, a rubber body plug.
Thread Starter
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Fleet Mechanic
Joined: Jul 2013
Posts: 1,997
Likes: 237
From: NE Ohio
wanted to add some closure to this post.
New radiator cap has solved the overflowing issue. Temps are much more stable now as well.
With radiator completely filled, I hardly see any to very little overflow now.
The cap on it looked old but it didn't seem like it was bad.
Old cap when the truck hit 200 and I shut it down, you could hear it overflowing, new cap you can't even hear if it's overflowing and it doesn't fill the overflow reservoir like before.
That was also with a radiator not filled completely to deal with the overflow, now with it topped off, it behaves like it should.
Appreciate the input on this.
New radiator cap has solved the overflowing issue. Temps are much more stable now as well.
With radiator completely filled, I hardly see any to very little overflow now.
The cap on it looked old but it didn't seem like it was bad.
Old cap when the truck hit 200 and I shut it down, you could hear it overflowing, new cap you can't even hear if it's overflowing and it doesn't fill the overflow reservoir like before.
That was also with a radiator not filled completely to deal with the overflow, now with it topped off, it behaves like it should.
Appreciate the input on this.
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