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V Mount rad cooling issue, HELP!

 
Old 07-08-2019, 01:16 PM
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Default V Mount rad cooling issue, HELP!

Hi all,


Im nearly finished with my turbo build (at least I thought I was)!

On my mk1 95' 1.8 I have V-mounted (or 7 mounted) my Rad/intercooler set up. Ran the car up for about 15 mins and coolant started boiling so turned it off, tried bleeding it with the front jacked up slightly and using a funnel, heaters werent getting warm, hoses werent hot but engine started getting hot so turned off and left it, so here I am asking for help.

Ive drawn a rough picture/diagram of the coolant set up, please tell me if its a crap set up or if its a set up that isnt going to work. Ive relocated the reservoir to where the washer bottle used to sit (RHD car) and using this as a coolant fill point as well as my rad hasnt got a fill point/cap just inlet and outlet.


The set up is Tank/reservoir T'eed into reroute hose. Reroutehose from stat housing (relocated to rear of engine) to top of rad then hose from bottom of rad to engine.


The main issue is not having any bleed screw points in the system and rad being so low down, which is obviously causing a major air lock / pocket of air.


Need some help/advice on how to get the airlock out with the rad being so low down.






Drawing to show angle of pipes/hoses



Thanks in advance
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Old 07-10-2019, 11:09 AM
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Is the radiator return still going to the mixing manifold at the water pump Inlet?

Do you have an OEM style thermostat with the bleeder hole located in the 12 position to allow air to pass? If not you should remove your thermostat and drill a little hole in the 12 position to allow air to pass out of the back of the head. That will likely solve your problem.
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Old 07-10-2019, 01:00 PM
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Originally Posted by sixshooter View Post
Is the radiator return still going to the mixing manifold at the water pump Inlet?

Do you have an OEM style thermostat with the bleeder hole located in the 12 position to allow air to pass? If not you should remove your thermostat and drill a little hole in the 12 position to allow air to pass out of the back of the head. That will likely solve your problem.
Yes radiator return still goes to where the original hose came from.
I used the OEM thermostat from the front and just relocated it to the back when I did the reroute, I cut the jiggle pin off the thermostat before installing it and 99% sure i put it at the top. I have now ordered a new thermostat which opens at a lower temp which should arrive by the weekend. So if its not the thermostat causing the issue then need to figure out how to get the coolant circulating and figure out how to bleed the system
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Old 07-10-2019, 01:44 PM
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Heater return. Does the heater return still go to the water pump Inlet mixing manifold?

Thermostat opening temperature is of no value if the thermostat does not have coolant touching it because the back of the engine is full of air. Thermostat must be contacted by coolant for it to open. Hot air won't get you there.
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Old 07-10-2019, 01:45 PM
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Who's reroute system did you buy?
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Old 07-10-2019, 03:08 PM
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Originally Posted by sixshooter View Post
Heater return. Does the heater return still go to the water pump Inlet mixing manifold?

Thermostat opening temperature is of no value if the thermostat does not have coolant touching it because the back of the engine is full of air. Thermostat must be contacted by coolant for it to open. Hot air won't get you there.

Originally Posted by sixshooter View Post
Who's reroute system did you buy?
Not sure who it was from as I bought it second hand but I know the guy who had it before me was running the reroute with no issues.
Ive put some pics up of when the guy before me had the rad set up, he sent me these pics and this is how its fitted on mine, you can see where the outlet rad hose goes to and thats the only pic of the stat housing from the reroute ive got unfortunately.




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Old 07-10-2019, 03:54 PM
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I don't have enough information yet to help you solve the problem.

What I can see is that you will have great difficulty getting air out of the top 25% or more of that radiator. It is very poorly designed and probably why someone sold it. At this point I can suggest having a threaded bung welded into the highest point of one of the radiator end tanks and another in your swirl pot (or pressurized expansion tank) and connecting the two.

Other things still have no clarity.
1. Does your heater core connect to the pipe that runs beneath the exhaust manifold and then into the mixing manifold Inlet for the water pump?
2. Does the heater get water from the reroute spacer or some other location?
3. Is the thermostat located between the spacer and the head or between the spacer and the outlet flange?
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Old 07-10-2019, 04:31 PM
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Originally Posted by sixshooter View Post
I don't have enough information yet to help you solve the problem.

What I can see is that you will have great difficulty getting air out of the top 25% or more of that radiator. It is very poorly designed and probably why someone sold it. At this point I can suggest having a threaded bung welded into the highest point of one of the radiator end tanks and another in your swirl pot (or pressurized expansion tank) and connecting the two.

Other things still have no clarity.
1. Does your heater core connect to the pipe that runs beneath the exhaust manifold and then into the mixing manifold Inlet for the water pump?
2. Does the heater get water from the reroute spacer or some other location?
3. Is the thermostat located between the spacer and the head or between the spacer and the outlet flange?

Im wondering how others with MX5s have done their set up with a V/7 mount, I know not many people have gone Vmount but i know its been done a few times, just cant see any info and really want this sorted as this is the only thing putting my turbo build on hold.
You mean connect a hose pipe from rad to expansion tank? what about fitting/welding a bleed valve/screw to the rad and have a bleed valve in the hose near the stat housing?

1. Yes both heater cores are still connected
2. Heater gets water through the spacer which has an outlet pipe so uses the same oem hose/pipe from heater
3. Im pretty sure the thermostat is located between spacer and outlet flange from what I remember from when I fitted it.
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Old 07-10-2019, 05:49 PM
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Low-mounted radiators require bleed/fill lines. Typically you have two ports, independent of the main inlet/outlet. The first port is at the highest point of the top tank for a vertical flow rad like yours, with a hose running to a high-ish point on the side of your expansion/fill tank. This can be smaller, -6 AN or so. The second port is in the bottom endtank, with a hose running to the lowest point of your expansion/fill tank. This is the drain for your expansion/fill tank and the hose is larger, since you're filling the cooling system from the lowest point via this hose. -10 AN or larger ideally, it could be a bit smaller but would to take forever to fill.

These two hoses are independent of the cooling system's main flow path.
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Old 07-10-2019, 05:54 PM
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The bleed screw won't work like a line to the expansion tank will. A line to the expansion tank will always help any air that happens to get free make it out of the radiator and up to the highest point. Burping can be a long process in a system designed like that. A permanent line will be self burping and allow you to maximize cooling in perpetuity.

If you do just put a bleeder on there it needs to be set up to seal to a hose connected to a funnel held as high or higher than the expansion tank while the engine is running through several heat cycles.

And you might want to drill out the tickle hole in your thermostat a little to aid the air in passing when you are checking it for 12 O Clock High.
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Old 07-11-2019, 12:14 PM
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Originally Posted by ThePass View Post
Low-mounted radiators require bleed/fill lines. Typically you have two ports, independent of the main inlet/outlet. The first port is at the highest point of the top tank for a vertical flow rad like yours, with a hose running to a high-ish point on the side of your expansion/fill tank. This can be smaller, -6 AN or so. The second port is in the bottom endtank, with a hose running to the lowest point of your expansion/fill tank. This is the drain for your expansion/fill tank and the hose is larger, since you're filling the cooling system from the lowest point via this hose. -10 AN or larger ideally, it could be a bit smaller but would to take forever to fill.

These two hoses are independent of the cooling system's main flow path.
I dont suppose you have a picture or could draw something up (maybe using my pic on the 1st post) of the set up youre talking about could you? Im trying to figure out in my head how this is supposed to be.
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Old 07-11-2019, 12:41 PM
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Originally Posted by sixshooter View Post
The bleed screw won't work like a line to the expansion tank will. A line to the expansion tank will always help any air that happens to get free make it out of the radiator and up to the highest point. Burping can be a long process in a system designed like that. A permanent line will be self burping and allow you to maximize cooling in perpetuity.

If you do just put a bleeder on there it needs to be set up to seal to a hose connected to a funnel held as high or higher than the expansion tank while the engine is running through several heat cycles.

And you might want to drill out the tickle hole in your thermostat a little to aid the air in passing when you are checking it for 12 O Clock High.

Would you be able to draw where this permanent line should be? I think ill understand it better if I see it in front of me. Thanks
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Old 07-11-2019, 12:46 PM
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Your drawing shows only one hose going from the tank to the rest of the cooling system, so there is at least one thing missing straight away.

An expansion tank for a low-radiator setup like you are doing should have three ports, not counting the radiator cap:



The "Bleed" port on the side is how your cooling system self-bleeds air out of the system. Any potential high-points in your cooling system where air could be trapped with no escape route should be identified, and then run hoses from those high points to this bleed port. At minimum, there should be one hose here; going from the highest point in your radiator's endtank (above the main inlet hose) to this bleed port on the expansion tank. Many cooling systems have more than just one potential air trap though, so it's not uncommon to see a hose running from each of those points, which all tee together and eventually end up at this bleed port on the side of the expansion tank. These lines can be relatively small, -6 AN is what I typically use.

The "Fill" port is on the bottom of the expansion tank. This must run via a larger hose, minimum -10AN, to a low-point in the cooling system; usually the bottom endtank of your radiator (on a Miata you could Tee this into the lower radiator hose). When you fill the cooling system via the radiator cap opening on the expansion tank, your coolant passes down this fill hose and fills your cooling system from the lowest point in the system up.

Third port is the overflow, which on a street car should run to a simple overflow bottle, such as the factory plastic Miata overflow tank.

The expansion tank should only be filled about 1/2 to 2/3 up, with water level below the bleed port , never full.
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Old 07-11-2019, 01:04 PM
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This gets you to square one with the expansion tank set up properly, instead of how it is now. If there are other issues in the cooling system, at least then you can move on to identifying/addressing those.
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Old 07-11-2019, 01:36 PM
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Originally Posted by ThePass View Post
Your drawing shows only one hose going from the tank to the rest of the cooling system, so there is at least one thing missing straight away.

An expansion tank for a low-radiator setup like you are doing should have three ports, not counting the radiator cap:



The "Bleed" port on the side is how your cooling system self-bleeds air out of the system. Any potential high-points in your cooling system where air could be trapped with no escape route should be identified, and then run hoses from those high points to this bleed port. At minimum, there should be one hose here; going from the highest point in your radiator's endtank (above the main inlet hose) to this bleed port on the expansion tank. Many cooling systems have more than just one potential air trap though, so it's not uncommon to see a hose running from each of those points, which all tee together and eventually end up at this bleed port on the side of the expansion tank. These lines can be relatively small, -6 AN is what I typically use.

The "Fill" port is on the bottom of the expansion tank. This must run via a larger hose, minimum -10AN, to a low-point in the cooling system; usually the bottom endtank of your radiator (on a Miata you could Tee this into the lower radiator hose). When you fill the cooling system via the radiator cap opening on the expansion tank, your coolant passes down this fill hose and fills your cooling system from the lowest point in the system up.

Third port is the overflow, which on a street car should run to a simple overflow bottle, such as the factory plastic Miata overflow tank.

The expansion tank should only be filled about 1/2 to 2/3 up, with water level below the bleed port , never full.
I think im understanding it now. So would you say run a hose from top of rad (get a point welded on) and maybe a hose onto the reroute hose close to where the tank is T'eed into at the moment and then connect these two hoses and fit them to the Bleed point on the tank and relocate a new tank to T into the lower rad hose?

The expansion tank Ive got at the moment is this one, would I be able to drill and fit a bleed point to this tank or should I get a new tank?

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Old 07-11-2019, 02:47 PM
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Originally Posted by mmarques88 View Post
I think im understanding it now. So would you say run a hose from top of rad (get a point welded on) and maybe a hose onto the reroute hose close to where the tank is T'eed into at the moment and then connect these two hoses and fit them to the Bleed point on the tank and relocate a new tank to T into the lower rad hose?

The expansion tank Ive got at the moment is this one, would I be able to drill and fit a bleed point to this tank or should I get a new tank?
That tank could work if you add a bleeder port on the side of it. The bottom port is low enough that it can work as the fill outlet but it's pretty small so it's going to take a long time to fill the whole system using that tank as the fill point. If you're already modifying this tank, take the extra time to put a larger fill port in the bottom and just plug/block off that old one.

Regarding the bleeder port/hoses, yes you want to weld a new port on the top of the radiator to run a hose to the bleeder port on the expansion tank. That second half of your sentence is a little confusing, the upper reroute hose itself isn't really going to be a high point that would require bleeding air from. It's more likely that there is a higher point than the hose in the machined reroute block itself on the back of the head. A bleed hose at that point could be beneficial... but I would start with just the one very important bleeder hose going from your radiator to the expansion tank, get that routed right and go from there.
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Old 07-11-2019, 03:22 PM
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Originally Posted by ThePass View Post


This gets you to square one with the expansion tank set up properly, instead of how it is now. If there are other issues in the cooling system, at least then you can move on to identifying/addressing those.

Just seen this, So scrap the bit youve crossed out and add the two hoses. Can the overflow pipe just be left venting ie not going into an over flow tank?
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Old 07-11-2019, 03:53 PM
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Originally Posted by mmarques88 View Post
Can the overflow pipe just be left venting ie not going into an over flow tank?
In terms of cooling system function, that is fine. The overflow hose is just a last-resort escape route for coolant if the cooling system pressure exceeds the cap's rating (i.e. when you overheat). However, you don't want coolant spraying all over your engine bay or getting on your tires, and more importantly, for environmental reasons it's preferred to dump the coolant into a reservoir of some kind, any kind rather than just dump it on the ground.(I've used a Gatorade bottle with the overflow hose zip tied to it in a pinch).
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Old 07-11-2019, 04:16 PM
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Originally Posted by ThePass View Post
In terms of cooling system function, that is fine. The overflow hose is just a last-resort escape route for coolant if the cooling system pressure exceeds the cap's rating (i.e. when you overheat). However, you don't want coolant spraying all over your engine bay or getting on your tires, and more importantly, for environmental reasons it's preferred to dump the coolant into a reservoir of some kind, any kind rather than just dump it on the ground.(I've used a Gatorade bottle with the overflow hose zip tied to it in a pinch).

Ok, thanks for clarifying, I shall do something similar and dump it into a reservoir/bottle of some sort.

Just a couple more questions if you dont mind me asking;

Is the expansion tank best kept where it is against the bulk? Im just wondering because of how tight and hot that side will be with running the new hose and T'ing into the outlet hose was wondering if it could be moved to where there oem tank sat but then it would be sitting slightly lower than it would if it was against the bulkhead.

Ill try and find someone local who can weld a fitting to the rad and 2 new ones to the tank.
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Old 07-12-2019, 01:52 AM
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As long the the top of the expansion tank is the highest point of your cooling system, you can put it pretty much anywhere you want.
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