Built a new engine this season, same combination only thing different is a different block.

Got it running and had coolant leaking out of 3 header bolts. Ender up epoxying the threads and using longer header bolts, leaks fixed..... , loaded it in the trailer and went to VMP for the ST Patricks day race. Ended up putting about 30 runs on it that weekend and everything ran good. By the time we got home, it had leaked a bunch of coolant all over the trailer. Turns out it had leaked from the waterpump gaskets and the intake gaskets ???? I was sure I was gonna find an oilpan full of water as the radiator was real low. Oil was crystal clean, actually the cleanest breakin oil I've ever had, no water .

Fast forward ......... Changed the intake gaskets and water pump gaskets and went racing. For the record........ I've never had a intake gasket or water pump gasket leak before this, so it seemed odd. Ever since we went with these new Brodix CNC 305 heads, the engine has always ran hotter and builds heat quicker and just keeps climbing even with the water pump and fans running, something it never used to do. It's manageable, but definitely noticeable. I kinda chalk it up to its making a lot more power than our previous combo's ???

So this past weekend, its hot and muggy and the kid says the cars not cooling down as quick as usual. Turns out the hoses are rock hard and the overflow is full ??? He drains the radiator and overflow and refill with some fresh water and continues on. KEEP IN MIND, the car runs perfect and does not overheat, never gets above 190 even on a 90+ degree day. Run 1 after draining it, hose is firm, run 2 hose is firmer, run 3 hose it harder yet but nothing in the overflow. Race gets called rd 3 due to rain. Load up and that leads us to the final chapter ............

In the trailer, 5 days later the system is still fully pressurized, hose is rock hard !!! Little bit of coolant in overflow, not much. We open the system and start checking things from top to bottom while cold. Here's what's convinced me I'm stumped ....... For 20 years, I've been filling the radiator to about and inch or so from full, put the cap on and go racing, now when I do that the radiator is less than 1/2 full with the water pump running ???? Air bound right ??? Well, I figured I'd fill the system with the waterpump running, held almost a gallon more water and was flowing nice. Put the cap on, ran the pump a little longer and let it sit. I figured if its overfull it will puke, never puked. I opened the cap and water was right up to the top, totally full. Things we looking good and everything made sense why it wasn't cooling down as quick, radiator less than 1/2 full will do that right .

Well .......... Next day the system is rock hard !!!! I mean ROCK hard. Overflow was full and the system was fully pressurized !!!! The damn thing never even ran !!!!! I took the cap off slowly and it was barfing fluid like it was 300 degrees !!! How the hell did it build that much pressure just sitting in the trailer ?????


I've kinda given up on a bad headgasket, and I'm almost convinced it's an air bound problem, but what now ???

Sorry for the long post, it was even painful to write


Any ideas ?????

A couple pages back on may 15th there was a thread something like this, Radiatior cap pressure when cold. Are you using anything in your water? Might want to get one of the test kits to check for exhaust in cooling system. Strange problem for sure .I had a pontiac with the head bolts bottoming one time. Head gaskets leaked combustion pressure into water jacket and would push water out. I took water neck off manifold ,filled block to top and water pump not on. I started engine and was able to see bubbles.

Pressure without ever starting it... electrical potential is the most obvious answer but it could also be sucking air during ambient heat cycles. This could be a bad radiator cap and or an overflow that doesn't allow water to return.

Does your overflow return water durning cool down?

Is your radiator grounded?

What fluid are you running?

Pressure from the combustion chambers is being pushed into cooling system. Either a porous head or head gasket. I had it happen on a head that was repaired. Strange that the cap is not opening, what pressure is it? It should fill the overflow.

quote:

Pressure without ever starting it... electrical potential is the most obvious answer but it could also be sucking air during ambient heat cycles. This could be a bad radiator cap and or an overflow that doesn't allow water to return.Does your overflow return water durning cool down? Is your radiator grounded?What fluid are you running?

Radiator cap is a new 7psi, had an old 7psi and a new 16 psi. All did the same thing. Overflow is new this season hmmmm ?? Had an old plastic Jazz for 20 yrs, now we have a shiny billet one, not sure of manufacturer??? I assume it does not return,Radiator is not grounded. right now running straight water .

quote:

Pressure from the combustion chambers is being pushed into cooling system. Either a porous head or head gasket. I had it happen on a head that was repaired. Strange that the cap is not opening, what pressure is it? It should fill the overflow.

I was all over the head gasket idea too, but would that hold pressure for so long ??? I'm more in line with a bad head, these Brodix heads are shyt as Ive had leakage problems with them already and they are less than 5 yrs old.

Still cant explain building pressure and lots of it, just sitting in the trailer. And why the radiator is only half full with the pump running yet full when the pump is off ??? I just ordered a raised manifold fill, hopefully that will cure the radiator water height issue.

Car runs perfect, wish it was something obvious ..........


Thanks for the replies !!!!

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Might want to get one of the test kits to check for exhaust in cooling system. Strange problem for sure .I had a pontiac with the head bolts bottoming one time. Head gaskets leaked combustion pressure into water jacket and would push water out. I took water neck off manifold ,filled block to top and water pump not on. I started engine and was able to see bubbles.

I just got one of the kits, I'll test that this weekend. I see bubbles with the pump running and engine off ???? Can a gasket leak one way only ??? This system hold pressure like I've never seen lol

are you using gasket sealer - The RIGHT STUFF on your pump to block interface?

If not I would recheck all the easy stuff. Like Rad hoses etc.

And to answer your question on air sucking in - yes it can happen easy. THe companies I own/operate run high temp sintering ovens that are fed with nitrogen/Hydrogen lines that are pressurized. Any leaks will suck in air - not always leak gas. The air leaks show on the belts and parts if excessive. Dimensionally on parts if subtle.

So yes even in a pressurized system it is possible to suck in air - is your application exactly the same. No - just saying it is possible.

Check your hose clamps, and all the easy stuff before getting into the internals.

What happens if you let the car warm up with the cap off? I used to have to do that with a car I used to run, then rev the motor with the mechanical pump and the fluid level would go down to fill it the last little bit to get all the air out - and then replace the cap with the idle still up and it would be perfect then.

Likely a chemical reaction you didn’t mention if you are running any additives in the water. You could also have some electrical current getting to the coolant. A filler neck will not help.
All ways fill you coolant system to the top with the water pump turned on and install the cap before turning pump off. Never open the radiator cap unless you pump is running!

What happens if you let the car warm up with the cap off? I used to have to do that with a car I used to run, then rev the motor with the mechanical pump and the fluid level would go down to fill it the last little bit to get all the air out - and then replace the cap with the idle still up and it would be perfect then.



I never tried that yet, On the list of things to try lol

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All ways fill you coolant system to the top with the water pump turned on and install the cap before turning pump off. Never open the radiator cap unless you pump is running!

Hmmmmmmmmmmm .......... Never had to do that before, but obviously now its a different story. I found it odd that it took almost a gallon of extra water to fill when the pump was running. It was even more odd that it built pressure just sitting there. Did take a day to do so I am running straight water now.

Tell me more of this chemical reaction / electrical current idea ........

And I even have a Meziere water pump

I'm thinking you have air building pressure. Heat up motor without cap, and pack system with pump running the whole time. Reinstall cap before shutting anything else off.... Once put back together.... It will be good. I think

If you get on youtube a couple of vid show you how to check.
https://www.youtube.com/watch?v=ZLLSwUGJvDw

Easyest way to check would be to diconnect the battery cables both neg and pos at the battery to see if the issue goes away.

As for the chemical reaction, I would try a complete flush with tap water or drinking water, then refill with the same and try a couple of bottles of water wetter.

Bob, are you running tap water or distilled? I've had tap water corrode the heck out of a brand new set of heads in a short period of time. Switched to distilled.......problem solved. Don't know if it has anything to do with your problem, but if i understand correctly, you filled the system with the pump running, then sealed it up and never ran the engine and it puked anyway? That says it's likely not a mechanical problem, but a chemical or elctro-chemical issue. I'm assuming you have good flow through the radiator with the pump running.

This message has been edited. Last edited by: Ralph85,

What did you find out Bob? Heard you were running sat so guess situation was not too serious.

Still kinda stumped, but all is good.

I did a coolant emission test and that turned out fine, so that's a big relief. Being it was still pushing coolant into the overflow every few passes, I was a little reluctant to fill the system to the top with the pump running like recommended but I bet with a recovery/expansion style tank and a higher pressure cap I can and hopefully I'll be good.

I have no idea why this set-up doesn't work like all my others but I'll figure out what it likes and hopefully wrap this little dilemma up.


Thanks for all the tips and ideas !!!!

Make sure your vent in your overflow tank is open. Mine clogged up once and cap would open but vent would not allow pressure to bleed off eventually pushed a radiator hose off.

All is good !!!

Hooked up a little recovery tank from a Nissan, upped the cap pressure to 16lbs and filled the radiator with the water pump running. Everything now works as it should

Thanks again for all the replies !!!!

I fill mine turned off, put the cap on and run the pump, repeat until the air is out. I have air bleeds where it traps air but if the pump is running they suck air. Dragster with radiator over the trans.