New motor drives great but after running for a few minutes the pressure in the cooling system gets really high There is no thermostat can that be the probem? I thought I wouldnt need one because I removed heater core and bypasssed it. My overflow tank fills and doesnt ever seem to be going back after cool down only put a bottle and a half of prestone so I dont think its overfilled. Please help I blowing hoses up. Its a 88 se 13b 6port carbed. The pressure is so high when I opened the overflow tank c ap I blew the hose that goes from back thermostat housing to back of engine on top If pics are needed Ill post them but I need help despretly. I didnt bleed air out but I never had to before when I replaced radiators or hoses all thats been changed is engine and the only difference is that this engine isnt running a thermostat.

 

sounds like the coolant seal going out and combustion gases are raising the pressure in the coolant system from direct contact w/ the coolant

 

Is there a way to check for that?

 

I think its because I didnt bleed the air out of the system. How do I do that? Just run the car with cap off the filler neck till its hot and expanded then cap it? There is no cap on the radiator just a pipe that runs to the overflo tank. Between the overflo tank and th top of the radiator is another cap should I replace that? Im going to mazda tommarrow to get oem thermostat. but i dont think thats the problem

 

There is a test to see if exhaust gases are in coolant system, it is chemical reactive liquid that changes color.

 

If it was the coolant seals, wouldnt coolant get inside the motor when it is not running and then smoke alot on startup. I had a motor with bad coolant seals that would smoke like crazy till it got warm. How to you bleed the air out of the system? the screw on side of radiator? Whats the process

 

you could also try replacing your pressure cap to see if that changes anything

 

I replaced the one on the filler neck but nothing changed I have to go the dealer Monday and get the cap that is between the overflow tank and top of radiator After doing some searches I found that I should have the tstat in but I doubt thats the problem

 

you may want to burp the system. however, i also think you should replace the caps (don't skimp either).

 

thermostat or no tstat?

 

always t-stat.

fire it up cold with the cap off and see if it smells like exhaust. also, see if coolant starts spitting out. dead givaway.

 

This is what Im doing. first Im letting car get hot then Im pulling cap off thats between top of rad and goes to overflo tank. Air and coolant with bubbles blast out for a sec. Then I replace theat c ap and remove filler neck cap and fill with water till its topped off and then Icap it and let it pressureize again then repeat the process. Am I bleeding it correctly? I was told that my whole problem is that Im using to much water and not enough antifreeze and the water is turning to steam and creating pressure. I thought it was possible to run just water without problems. I will be making it to the dealer today for a cap and tstat

 

Coolant ratio should not make any difference. Get the coolant tested for the presense of hydrocarbons. Combustion pressures are higher than coolant pressure so the coolant doesn't always show up in the exhaust with a blown seal.

 

When the car isnt running wouldnt coolant make its way into the engine and smoke during startup. Also, now after blleding air out a few times I drive for a while pressure on hoses is still there but its not filling the overflo anymore and its not pulling from the overflo while c ooling down.

 

You would think the combustion chambers would fill after shutdown, but I have seen them not do that and still pressurize the cooling system. If the coolant is not being pulled back into the system, either the radiator cap is bad/wrong or there is a leak in the return from the overflow to the cooling system.

Btw, the thermostat is for the engine, has nothing to do with the heater core. Install a new oem one.

 

I have the radiator without a cap on it but it has a hose on the top that goes to a cap by the hood latch which runs to the overflow tank. I will be replaceing it shortly. If it is a leak in the return, Can the leak from the return be pulling air in on cooldown and causing my high pressure problem? wouldnt it be a obvious leak when pressurized (coolant spraying)? Also if it is coolant seals allowing combustion gases into the waterjacket and its not pulling coolant back to the inside of the motor during cooldown, that kind of eliminates the chance of block weld working as a temp fix. right? Ive read that people with blown coolant seals have used the block weld fix on engines that spray coolant from the spark plug holes but mine seems to be doing the opposite and leaking from inside out to coolant system. Still no smoke still starts right up with perfect idle.

Can a cap really be causing all this trouble?

 

oh yeah and i know the tstat is for letting the engine get to operating temp and maintaining it. What I meant about heater core is cars without tstat take longer for the heat to work and i dont have heat in mine but thanks for the info. I hope I an get this thing running right soon its so pretty with the new painted engine and engine bay

 

You can get an air leak in the pickup tube in the overflow tank, won't show up, other than the coolant not returning to the engine. The rad/fill cap could be bad too.

 

This has happened to me before. The coolant seals were fine, I just had to thoroughly burp the system of air.

 

newest developments of the un burpable car. OEM Rad cap filler cap tstat. Now on cooldown it is pulling from the overflow. I went out there today after burping it a few times yesterday and discovered an empty overflo (usaully filled to brim) so I filled that. Can I ruule out coolant seals yet? Also, if its pulling coolant from the overflow now does that mean it was pulling air during cooldown before thus causing my rock hard super hot hoses? I decided to take a day off this problem and will get back to burping it again tommarrow.

 

If you are getting no smoke in the exhaust, with the pulling of the coolant, I would say you are running hot. I had an e-fan on my FC last summer that did the same thing, switched back to the stock fan as the e-fan was not pulling enough cfms on hot days in city traffic.

The gauge was going up to 3/4, with the defroster on full. As soon as I shut it down, it boiled over into the overflow, sucked it back when cool.

 

Still fighting with this thing and I began pricing out radiators and efans when my friend who painted the engine told me that the bottom half of the water pump was stained like it was leaking behind the pulley. Of course he tells me now and not before he paints it. Doesnt seem to be leaking now but Im changing it anyways. Could that create a high pressure problem? Its not spraying out. if it is leaking its very small but car still runs very hot with a swollen top hose. Today it decided not to pull back coolant from the overflow. Thanks again everyone

 

That is something I could never understand when people do rebuilds. They spend the money on a fresh motor , yet don't spend the little extra to protect it, i.e., new waterpump, t-stat, belts, hoses, service injectors, etc. Not picking on you, it's one of my pet peeve observations about doing a complete job. while the little parts do add up, it's still cheap insurance compared to another rebuild.

If you builder noticed the waterpump, ignored it and it is the cause of the overheating, he should be responsible for any overheating failure.

 

i've got a simular problem with hard hoses, no coolant returning to the rad, and just about everything you described... and i know i have a blown water seal. When you are burping the system do the bubbles every go away?

 

I have the same problem , just wait until the engine get really cold , and then started it with the radiator cup open , if you can see big bubles inside the coolan after a minute you blow a water seal. And you need to change it or rebuild the engine.
I have that problem 2 times in 3 diferent engines , it depend in wich side you blow the water seal if it get inside of the rotor or you get gas inside of the coolant system.
My recomendation is to rebuild the engine , with new rotor housings , and if it posible a realping of the lateral housings. For the relaping you can do it in www.racingbeat.com or in www.pettitracing.com , and for buy all the new stuffs you can do it in http://www.rotorsportsracing.com/ they have upgreated water seals and corner seal that works excelent , I have rebuild 2 engines with that kit and it really works , the only problem is that it is a pain in the *** to rebuild it with that water seals.