Hot 350 or not

[pcguy]

Ok, so I was not able to run the engine with the cap off because coolant went everywhere. So I took an old radiator cap, removed the lower rubber gasket and drilled a 3/16” hole in the stainless steel backing plate. Installed the cap removed the overflow hose and connected a 5/16” translucent plastic hose and put the end into a plastic milk jug, just in case.

Well, initially the fluid came up about 18'” and air started bubbling out and slowly the level came down and at times disappeared. I was somewhat concerned that what I was looking at was a head gasket problem, but eventually, I could race the engine (3-4k) and very little coolant would show and when it did, air also escaped. Have shut off and restarted numerous times and each time more coolant/air comes out and goes back to no coolant showing.

Could all this have to do with too much air?

[cjbiagi]

I don't understand why coolant would come out on a cold engine, you have some strange things going on. Normally the water pump would be circulating coolant so that it would be pulling it out the bottom of the radiator, through the engine and then back into the top of the radiator. I would definitely try and verify the water pump that you have on there and make certain it is flowing the correct way. Do you have a coolant recovery system on here? You definitely want one if you don't and make sure you have the correct cap which is designed for a closed system. I am just wondering if you do have a reversed water pump on there which may explain why it blows water out of the top of the radiator with a cool engine? With the cap off and no pressure built up you should be able to see the coolant flow especially if the coolant level is a little low so the top rows are exposed when you look in there. Coolant should be sucked out the bottom of the radiator, not blowing out the top...........
A bad head gasket will show up as bubbles in the cooling system but you need to get the air out first to verify that. It also generally shows up as white smoke out of the exhaust and your coolant level may be dropping. Any signs of coolant in the oil?

[pcguy]

I don't understand why coolant would come out on a cold engine, you have some strange things going on. Normally the water pump would be circulating coolant so that it would be pulling it out the bottom of the radiator, through the engine and then back into the top of the radiator. I would definitely try and verify the water pump that you have on there and make certain it is flowing the correct way. Do you have a coolant recovery system on here? You definitely want one if you don't and make sure you have the correct cap which is designed for a closed system. I am just wondering if you do have a reversed water pump on there which may explain why it blows water out of the top of the radiator with a cool engine? With the cap off and no pressure built up you should be able to see the coolant flow especially if the coolant level is a little low so the top rows are exposed when you look in there. Coolant should be sucked out the bottom of the radiator, not blowing out the top...........
A bad head gasket will show up as bubbles in the cooling system but you need to get the air out first to verify that. It also generally shows up as white smoke out of the exhaust and your coolant level may be dropping. Any signs of coolant in the oil?

Hi Clyde,

The pump does appear to be pumping in the proper direction – this morning, with the engine dead cold and the cap off, there was no evidence of flow until the thermostat opened.

As for the coolant coming out of the neck with the cap off, I figured out that because the thermostat/cap/neck are all together on the intake manifold and there is no space for moving coolant above the coolant level which is just below the seal in that very small chamber just above the thermostat. The raidator is a closed subject and there it no veiwing the inside.

This looks like the problem is either too much air in the system or a radiator that needs cleaning. Of course, I don’t have much experience with either.

This looks like the problem is either too much air in the system or a radiator that needs cleaning. Of course, I don’t have much experience with either. There are no leaks and there is a coolant recovery system. No smoke, no coolant in the oil and no oil in the coolant.

[cjbiagi]

Oh ok, obviously you have some different type of setup with the cap on the intake rather than on the radiator? If you have a functioning coolant recovery system it should naturally bleed the air out and keep the coolant level full, that's the function of such a system. It does rely on have a proper closed system radiator cap and no leaks. Whether or not the radiator has an issue with being plugged I don't know. It's still strange that the temps you were recording had the top of the radiator (hot inlet from the engine) cooler than the lower outlet (after the coolant passes through the radiator and gets cooled).

[pcguy]

Hey Clyde, I think the temp readings on the tank came as a result of taking the reading on the upper part at the wrong location – still a little confusing. I’m still not sure whether there is a head gasket leak or not. I will be taking a pressure reading from the closed cooling system when the engine is dead cold. Does it sound logical that there should be zero pressure at the radiator cap at that point and any observed pressure could indicate a leaking head gasket?

I did learn a bit about the Vette radiator in the Vega, which suggests in no uncertain terms that when there is no radiator cap on the radiator, there needs to be a pressure expansion tank with a radiator cap which is located on a fender well and mounted higher than the top of the radiator. A fitting in the top of the radiator connects a small pressurized hose to the tank and the tank has it’s own recovery tank connected traditionally to the cap neck just below the cap. Tried to insert a pic, but the image was too large and the tank was not in the pic. Need to study up on this one – the lower hose on the tank looks like it might be to the heater core???

[cjbiagi]

With the engine stone cold there should be no pressure in the system, heat is what builds pressure. Tht's why you always want to wait to remove the radiator cap from a hot engine. Your setup is rather different than a regulr H body one so pics would help.........

[cjbiagi]

With the engine stone cold there should be no pressure in the system, heat is what builds pressure. Tht's why you always want to wait to remove the radiator cap from a hot engine. Your setup is rather different than a regulr H body one so pics would help.........

[cjbiagi]

With the engine stone cold there should be no pressure in the system, heat is what builds pressure. That's why you always want to wait to remove the radiator cap from a hot engine. Your setup is rather different than a regular H body one so pics would help.........

[pcguy]

Might be a little confusing, but here goes. Right in the center is the radiator cap and the translucent hose coming of the neck on the left is the same hose coming back down on the right – it is then connected to my vacuum gauge. The way I made this work was to remove the lower rubber sealing gasket from an old cap and then drilled a 3/16” hole in the base behind that gasket. This allows the system to be sealed for pressure and to force any pressure into the translucent tube where I can see any coolant/bubbles.

Here’s a picture of my setup with my pressure test still in place – BTW, I ran the engine this morning, stone cold, with this setup/vacuum/fuel pressure gauge in place this morning and the only motion on the needle was a very slight movement toward vacuum. This seems reasonable because the water pump would be pulling on the cap and that provides some indication that a head gasket leak is less likely, at least when the engine is cold.



Hope this helps.... :thumbs

[NVEGAR8D]

Hi,
Sorry to jump in but, as i see it , you would get a lot better cooling by creating a shroud around the fan to really assist in drawing cool air through the rad and bringing down your temps.
nick75vega

[cjbiagi]

A shroud is absolutely necessary, go back and read the suggestions on cooling and you should be good. I hope to be getting some H body fan shrouds soon.

[pcguy]

I'm aware of the benefits of a shroud, however in this case, I only experience high heat at 60+mph and not at lower speeds. Even at idle for extended periods, the temp never goes over 180. Also, there is zero room for a 360 degree schroud - I have looked at it carefully and the only thing that is plausible is some sheet metal on the sides and bottom.

Can't recall if I mentioned it above, but the 2500 cfm, the electric pusher fan is set to come on at 165 and runs constantly.

Most notably in ths same regard is the fact that most engines don't require any kind of fan at highway sppeds. I will try to get it out for a road test today - I may have gotten the air out.

[cjbiagi]

Overheating at freeway speeds generally relates to coolant flow rather than air flow as you are suggesting. What kind of hoses are you running? Do you have spring in the lower hose? The lower hose can actually collapse at higher speeds and restrict flow, the spring is in there to prevent that. I also prefer molded hoses rather than the flexible ribbed ones as they flow better. Your temps really don't seem unreasonable, you my want to look into your total ignition timing as that can play a role in temps.

[pcguy]

My test setup here suggests that the coolant is flowing freely at speed and the lower hose has a spring, but as I understand the new rubber compounds don't require the spring any longer. In any case, I am still getting air out of my test hose - hope to road test it today, with and without vacuum advance.

Will be installing an expansion tank vs an overlow - that will move the radiator cap higher with expansion under it, and augment the overflow container. The problem is space - there isn't much.

[pcguy]

Well, I’m shooting at a target with inconclusive bullets – LOL. After all my testing it appears that the radiator may not be flowing freely. It’s vintage corvette 4-core brass, that may have seen better days. Thought about replacing it early on, but couldn’t find an off the shelf new one that would work.

Here’s where I am with my testing. After feeling confident that I have removed all the air, I disconnected the vacuum advance and drove the beast into town. Living on the coast with normal temps in the low 60’s, it’s hard to test an engine that runs hot. It really never overheats with coolant all over the place even when shut down at 220 with the fan running (except after running the traps at Sonoma Raceway – aka Infineon). When I head inland and the temps get into the high 70’s, the engine temp seems to follow the ambient temps and starts to increase and when I finally get to the freeway the engine is running a 215-220 temp. The electric fan helps, when I turn the engine off I can get the temp back to 200 or less in a very short time if I leave the fan running.

As I head back to the coast, the engine temp comes back to under 200, as it did yesterday. So when I got back I let the engine cool down to the point where I could safely open the radiator cap (it’s not on the radiator, it’s on the thermostat housing and it’s the highest point in the cooling system – see pic above). With the cap off, I started the engine and at idle the coolant immediately bubbled out of the housing. So I guess I need to find out what to do about the radiator.

My thought was to rig up a tight garden hose connection and see if I any sediment come out into a collection pan, or I can take a chance and have it boiled out, or I can have it re-cored. Open to some thoughts here.

Oh, and after it started bubbling over and just after I turned the engine, I tested the accuracy of the dash gauge by comparing the infrared reading of the coolant at the housing – was within 2 degrees at 173.

Thanks again you guys,

Nick