I have a 4.9 in my Fiero with a 3 core aluminum rad up front. In the rear, above the engine I added a Moroso fill neck adaptor. This adaptor takes a regular rad cap and has an outlet for an overflow bottle. Do I add an overflow bottle at this point [engine end of car] when I am using the stock one up front? Also what pressure of rad caps should I try first?, and should the front and rear caps be of the same rating? Thanking in advance as I am a body man, not a mechanic.
Thanks for quick response. So I ask the parts counter for a non venting rad cap? And so there is no need to plug off the small tube exiting the neck of the Moroso filler?
I moved my overflow to the back. One of the favorite mods I've done to my car. Actually I purchased a "parts store" overflow/recovery bottle, and mounted in the back, and connected it to the fitting on my Moroso fill adapter. I removed the front overflow, completely, and installed a 20 lb cap. In the back I installed a ~15 lb cap. This places the overflow at the highest point in the system.
Why did I deem this necessary? The 4.9, as installed at the factory, required "stop leak" tablets to be added to the system, to seal around the liners, block, and head gaskets. When those tablets are installed in a Fiero, they leave a gritty deposit on the radiator cap valve. Enough of a deposit that it can actually prevent a good seal, and allow the coolant to leak out into the overflow, and to continue overflowing on to the ground. In a perfect world, with a perfect cooling system, this wouldn't happen. My 4.9 has proven to be a different story. Since i made this change, I haven't had to add coolant in a very long time. Whereas before, I had to add coolant every 3rd or 4th drive.
That is an interesting story about the "stop leak tabs" Actually wouldn't it make sense to have the overflow bottle at the highest point? I have noticed as I try to get all the air out while filling at the engine filler, my front overflow will .............overflow!
Originally posted by Daleford: ... Actually wouldn't it make sense to have the overflow bottle at the highest point? I have noticed as I try to get all the air out while filling at the engine filler, my front overflow will .............overflow!
That's kind of what I was thinking. As long as the system is clean and well maintained, and is functioning properly, it works fine in the stock location. In the real world, with our cars 25 years old, it has its limitations. With it at the highest point, at least if it leaks, gravity won't empty half of the system.
OTOH... If yours is leaking out, just while being filled, there is something wrong. Perhaps you have the wrong radiator cap. A while back, STANT listed the wrong cap for our cars. The one we need is the one that holds the little disk against the bottom of the cap with a spring. If the disk dangles loosely against the cap, it's the wrong one. See the "ogre's cave" link at the top of the page. It's in there.
[This message has been edited by Raydar (edited 05-11-2015).]
Yes. You can plug it if you want, the non venting cap will stay sealed no matter the system pressure.
So my parts guy found a non venting cap and it is on its way. However he says it has a 16 pound rating??? Why would it have a rating to handle only 16 pounds if it is never going to vent? Or do I not understand something here. Again, NOT a mechanic.
I put the stock v6 thermostat housing/filler neck on my 4.9. It has a non-vented cap. It also houses my fan sensor and temp sensor.
I put a 3 core rad in the front and have no issues at all, except, on hot days I still wonder if I want to install an oil cooler. Normally, no issues though
I put the stock v6 thermostat housing/filler neck on my 4.9. It has a non-vented cap. It also houses my fan sensor and temp sensor.
I put a 3 core rad in the front and have no issues at all, except, on hot days I still wonder if I want to install an oil cooler. Normally, no issues though
I did that too and it always leaked. Had to throw it away and get a Moroso unit that will accept a real rad cap.
So my parts guy found a non venting cap and it is on its way. However he says it has a 16 pound rating??? Why would it have a rating to handle only 16 pounds if it is never going to vent? Or do I not understand something here. Again, NOT a mechanic.
The terms vented and non-vented have to do with the take-up process as the fluids cool.....not the pressure limits when hot. You want a 16 lb. cap in front, but in the rear, there is no over-flow line or bottle....so it does not matter..(If you put in the overflow system like Raydar did, then it does matter)..If you choose to use 2 overflow bottles, both caps should have the 16 lb. rating.
My NAPA store gave me what they call a non-vented cap that seems to be doing the job. No more leaks at the Moroso filler. The cap is a NAPA Balkamp part number 703-1698. Looks like a normal cap to me and the cap itself and the box it came in doesn't say non-vented. A google search didn't help prove anything either. I'd like to know for sure that it is non vented.
Well, I spoke too soon. This is why I hate mechanic work! Last evening I let it warm up and all worked well. New aluminum rad done its job, temp stayed normal, electric fan cycled as it should and finally. I have a fill point back at the 4.9 that didn't leak. [that is where I had installed the Moroso filler and the 703-1698 cap] Tonight I added a small amount of coolant and warmed it up again. The overflow pipe on the filler spit out coolant! Not a lot and only a small bit at a time. I feel like adding an overflow bottle to that pipe but....... I shouldn't have to. GRRRRRRR I'm going for a ride in my Mustang.
Go ahead and add the overflow at the fill neck. It's normal for it to push some coolant out, when the coolant expands, or when an air bubble "gets loose". Having an overflow bottle ensures that any coolant that gets pushed out (overflowed) will get sucked back in, instead of air being sucked in, in its place. Even the stock configuration has an overflow/recovery bottle. Retaining it - but moving it to the rear - is an improvement, IMHO.
[This message has been edited by Raydar (edited 05-13-2015).]
Go ahead and add the overflow at the fill neck. It's normal for it to push some coolant out, when the coolant expands, or when an air bubble "gets loose". Having an overflow bottle ensures that any coolant that gets pushed out (overflowed) will get sucked back in, instead of air being sucked in, in its place. Even the stock configuration has an overflow/recovery bottle. Retaining it - but moving it to the rear - is an improvement, IMHO.
I'm back .... so do you mean, add a second overflow bottle at the rear? or move my front bottle to the rear?
If the pressure max is 16 lbs on both caps, you will need an overflow bottle on both front and back. If you remove the bottle from the front, you should install a cap with a higher psi, so all the overflow activity is at the engine.
Do not remove front expansion tank, the radiator must have a way to purge air from the system. The radiator also serves as an air trap, and will trap system air with or without an expansion tank at the engine. Your NAPA guy should have ordered a cap that does not vent; he didn't, he ordered a cap that vents at 16 pounds. Put a 20 or higher on the engine and 16 on the front. No expansion tank needed on the engine.
Your NAPA guy should have ordered a cap that does not vent; he didn't, he ordered a cap that vents at 16 pounds.
Joe, pressure max and venting are 2 different functions. The cap will release pressure at 16 lbs. It will vent at 0 pounds or less when the coolant contracts and goes from the overflow bottle back into the system.
Do not remove front expansion tank, the radiator must have a way to purge air from the system. The radiator also serves as an air trap, and will trap system air with or without an expansion tank at the engine. Your NAPA guy should have ordered a cap that does not vent; he didn't, he ordered a cap that vents at 16 pounds. Put a 20 or higher on the engine and 16 on the front. No expansion tank needed on the engine.
That was the whole point of this discussion. To move the overflow to the highest point. I installed an overflow/recovery bottle at the filler neck that is at the engine. 16 lb cap on that filler neck. I installed a 20 lb cap on the radiator, and removed the front overflow, since the rear cap will now always vent before the front has a chance to. Any air that is in the system (provided there's not so much that the water pump cavitates) will make its way to the rear, and to the high point. If anything, it makes the system "self burping". It has been quite trouble free for the 2-3 years since I moved it.
[This message has been edited by Raydar (edited 05-14-2015).]
Joe My NAPA guy ordered a non-vented cap. Why are you saying: QUOTE: Your NAPA guy should have ordered a cap that does not vent; he didn't, he ordered a cap that vents at 16 pounds. It says "non-vented" on the box. It has the dime sized bottom valve spring-loaded as the Ogre describes in the link earlier in this thread.
The latest: It was easier to add a temporary overflow bottle at the engine and attach to the Moroso filler since I am not close to a parts store. I made a test run. All went well. The hot engine put about a pint of coolant out the Moroso filler into the temp overflow, and sucked it back into the system again when things cooled down. If this 2 overflow system will work I may leave it this way. Perhaps it would be best to put a 20 pound cap up front at the rad?
Perhaps terminology is our enemy.... "Non-venting", to me means it does not open under pressure. "Vented", to me, has a pressure relief lever. A " pressure cap" opens at a specified pressure value.
A question......how will any trapped air get out of the top of the radiator with a higher value pressure cap on the radiator? The radiator fills at the top and discharges from the bottom. What keeps the radiator from catching and filling with air over time?
I moved my overflow to the back. One of the favorite mods I've done to my car. Actually I purchased a "parts store" overflow/recovery bottle, and mounted in the back, and connected it to the fitting on my Moroso fill adapter. I removed the front overflow, completely, and installed a 20 lb cap. In the back I installed a ~15 lb cap. This places the overflow at the highest point in the system.
Same thing I am doing on my Countach build with a 350 Chevy engine only just happens my caps are 21 and 16 psi. Seemed like a no brainer to move the overflow to the back at the highest point.
A question......how will any trapped air get out of the top of the radiator with a higher value pressure cap on the radiator? The radiator fills at the top and discharges from the bottom. What keeps the radiator from catching and filling with air over time?
Answering a question with a question, if you are getting the air out of the system in the rear at the highest point in the system, where is this air coming from to "fill" the radiator?
Originally posted by olejoedad: ... A question......how will any trapped air get out of the top of the radiator with a higher value pressure cap on the radiator? The radiator fills at the top and discharges from the bottom. What keeps the radiator from catching and filling with air over time?
The flow of the water will force/carry it out. It's the same thing that happens when we burp our systems.
If you want to look at it from a different perspective, how does any air that is trapped in the engine get out, since the engine is higher than the radiator?
I know this is not new, but I also put a high pressure rated cap on the stock Fiero radiator location. I plugged the overflow vent for the radiator to prevent the ventilation of air into the radiator during cool down. Then put a 15# cap in the engine bay to purge the system from the highest point in the cooling system o my LS4.
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