hondahater

iTrader: (2)

Ok I'm not sure what could cause this. My car was running fine (maybe put 75 miles on it since the rubuild) I've been monitoring everything really closely however one day I noticed while I was in traffic that my temps where getting over 86-88*C which is the temp that I've got my microtech set to turn my electric fan on. Anyways while I'm sitting in traffic it edged up to about 99*C so I shut it off. I pulled over and noticed my coolant was really low. Well I filled it up with coolant and water and started monitoring it. Found that even when I take about 3/4 of the coolant out of the overflow bottle it ends up filling up quickly (not boiling into it) and then will start over flowing on to the ground. My over flow is basically comprised of a hose coming from the nipple under the upper radiator cap and goes to a stainless steel resevoir from summit. Any ideas what could cause this?

Stanello

iTrader: (1)

First thought would be a bad radiator cap. Sounds like it isn't holding pressure and just letting the coolant expand into the overflow.

hondahater

iTrader: (2)

hum....there's a thought. These are newish mazda caps but maybe one has gone bad? Thanks for the thought. I'll check it out.

jackhild59

iTrader: (7)

Another issue could be the size of the overflow tank. The OEM tank holds nearly a gallon of coolant. If your tank is small, it may not have enough room for the expansion, especially if the cooling system is not completely 'burped' of air.

Good Luck!

Go48

iTrader: (7)

Check the hose from the rad to the overflow bottle for a possible minute air leak. If that hose leaks air, the coolant will flow out of the rad into the bottle but will not be sucked back into the rad when the engine cools. In that case, coolant will build up in the overflow bottle and eventually fill the bottle.

SpeedOfLife

iTrader: (16)

^^^ that could be a tricky issue if you hadn't mentioned it.

Never assume that a new part isn't faulty! **** happens, even with brand new parts. At least rad caps are cheap.

hondahater

iTrader: (2)

Thanks for the input guys. The hose going from the nipple under the upper rad cap is stainless steel braided and has been working fine for a little while now and it's sort of hard to put a hole in ss line, this sort of just started happening all of a sudden. Now you guys may have point about the resevoir being too small. the summit unit may hold a half gallon at the most. Could there really be a problem with "too small" of a resevoir?

Go48

iTrader: (7)

Is the stainless steel hose clamped at both ends? If not, clamp it or try a regular rubber hose as a test. That hose has to be able to hold a vacuum. If it is leaking air at either connection point it will not function properly.

The overflow reservoir has to have enough empty space to accommodate the coolant that is dumped into it as the engine warms up. Half gallon seems large enough as long as there is enough empty space to accept the extra coolant as it expands into the reservoir.

misterstyx69

iTrader: (142)

I would check the hose clamps also..
if you got air in the cooling system,it is gonna expand and push the coolant out.Also the engine is gonna see hotter temps..(due to air,hot spot..).
..Try this:burp the System,check the hoses,clamps,and make sure rhe thermo is good,cap etc.
finally make sure that the Hose From the rad to the reservoir is Leak free,and tight.and the hose Under the reservoir Cap is ON,and is not cracked,It will not suck coolant back into the rad if that small hose is not there.The end of that hose must See coolant all the time.(Or your "give and take" rad system does not Function).

hondahater

iTrader: (2)

Well the stainless line has summit fittings as this stainless line is the expensive stuff, not the stainless sleeved hose so I know it's not the fittings. The other day I completely blead the system of any air. I'm going to turn it on today to see how it goes. Also I'll make sure the rad cap is ok. Maybe the system just had to much air in it Strange problem though as it wasn't doing this for the first 75 miles of driving it.

There is no hose going from the rad to the resevoir. That one is capped and the hose is going from under the upper rad cap on the thermostat housing to the resevoir. Does this make a difference?

RotaryEvolution

iTrader: (30)

the reservoir should rarely be seeing coolant pushed into it at all so the size of the tank isn't the issue. the issue is either the overflow line into the reservoir is acting like a one way valve, the coolant pressure cap is bad or the engine is pushing air into the system causing the coolant to be forced out.

it will if you have the pressure cap located on the radiator instead of the top of the thermostat housing where you have the overflow hose attached. but i would hope that you already realize this.

if you are using the plastic pressure cap adapter on the top of the thermostat housing you may have just told me the problem anyways. there is 2 issues with this plastic housing, a new o-ring that is too large may seal the housing to the neck but it will bow up in the center, not allowing the pressure cap to do it's job sealing internally properly and the plastic nipple going to the overflow tank can easily break off, especially under the additional weight of a stainless line vs the light rarely used OEM overflow line. i would suggest getting either a solid plastic upper adapter or an aluminum FD one, i use the FD aluminum one because it lasts forever vs the shitty plastic ones(which i have seen crack and leak a few times). the overflow line from the radiator is the best because it is the least likely to warp and cause a cap to not seal properly.

hondahater

iTrader: (2)

Actually the housing is aluminum from an s4.



The hole was drilled and tapped right under the upper rad cap. I'm going to swing by the store on my way home and get a cheepo rad cap just to see if this is the problem. Something just had to give because like I said this wasn't a problem at first. I highly doubt it's blown coolant seals just because I haven't over heated it at all.

RotaryEvolution

iTrader: (30)

oh well, i thought i had your problem solved... hoping it's just a radiator cap.

hondahater

iTrader: (2)

me too, only problem is both those caps are new from mazda. I've only run the car maybe 500 miles at most with these caps but of course that's with alot of time sitting inbetween miles. I probably bought them 3 or 4 years ago. I've been monitoring temps through my microtech and haven't alowed for any sort of over heat to occure but I guess anything is possible. I let it idle the other day with the cap off and it stayed right in between 84-88*C so who knows.

jackhild59

iTrader: (7)

Clean engine bay.

I would continue to focus on the 'one way' action of the cap, whether the cap is defective or there is a vacuum leak in the cooling system somewhere else.

I guess you still haven't pressure tested the system? I bet you are going to find a leak at a hose connection somewhere, radiator or heater. Bottom hose is pretty likely, heater alone has 6 places that it could leak etc.

Good Luck!

hondahater

iTrader: (2)

Well all heater lines have been capped off so really it shouldn't be there. My cooling system is very simple with brand new upper and lower rad hoses. Only thing can really be rad cap (maybe some residue from the powerder coating is making it not seat correctly) or coolant seal but I don't see this being it but I guess stranger things have happened.

Thanks for the compliment.

misterstyx69

iTrader: (142)

I am hesitant to comment on your setup.(coolant).with only the thermohousing seeing a hose to reservoir.
My 'custom" setup incorporates alot of what you Have,only I ran a reservoir hose to BOTH Caps.also both caps are Pressure relief caps(1.3 bar)
I ran a hose from Thermohousing to Reservoir and also from the Rad..The 'give and take "works fine.

hondahater

iTrader: (2)

both my caps are mazda pressure relief caps as well. I don't believe the stock setup has two lines going to the resevoir or at least mine didn't.

misterstyx69

iTrader: (142)

Ya..they Do NOT have two..but I made it have two,since both caps are Relief
.I didn't have a Stationary cap at the time and the thermohousing had a nipple so it would have been Counterproductive to put a stationary cap on.The coolant would have just went to overflow when it started getting warm,and would not hold pressure if so.
/My theory on YOURS it that it is Too high UP,and will have a tendency to get air from the Highest point,which is the thermohousing...NOW,If you take the Overflow from the rad,.at least it would give and Take Coolant,not any air.(since the rad is lower than the top of the thermohousing).

RotaryEvolution

iTrader: (30)

having 2 nipples just allows one more place for a faulty cap to allow coolant to push out of the system.

not needed.

hondahater

iTrader: (2)

I think you may be right on this one. I've always had the resevoir setup on the rad which worked great. This is the first time I'm pulling from the top like this and the first time I'm experiancing issues like this. I may just move it back.