So long story short, This 95 Civic ex 1.6l d16z6 had a blown head gasket. Car was overheating and bogging down/ losing power before finally cutting out. Had head resurfaced and replaced head gasket. First few days car ran great. No more bogging down and no more overheating. Then I blew a couple hoses (over the course of a few days) I had to open radiator cap to release pressure. After releasing pressure the car would start once again. I've since replaced the thermostat, (2) new radiator the Caps, radiator hoses, and the radiator. The car no longer overheats or bogs down and it maintains regular idle and power, but overtime pressure builds up in the after system andt off the car, it will not start unless I remove the radiator cap sometimes. Other times it starts up no issue. The only time I'm losing coolant is when having to remove the radiator cap to restart the car. There honestly is no linear path to this. One day everything is perfect, the next I have a pressure build up. It's also worth noting that occasionally when it stalls out, there is a very strong sulfer smell, but only sometimes. Please tell me someone has an idea of where I should go from this point?
​​​​​

 

It's quite possible the block is no longer flat from the overheats. As such, new gasket has failed and is putting pressure into your cooling system.

Or, you have shitty radiator caps, they should be 16 PSI caps. I think that is the 1.1 bar caps if I remember correctly.

 

Shouldn't be building pressure unless you used water as your coolant.

 

It sounds like the head gasket is leaking again.

Engine cold, loosen the cap to release any pressure then put it back on. Squeeze the top radiator hose to feel for pressure inside. Start the engine and rev it. If pressure builds up right away it is a head gasket leak. The pressure should not change much until the engine warms up. Then as noted it is normal to have some pressure.

But there's no physical way for pressure build up to prevent starting (unless the cylinders fill up with water, and in that case removing the radiator cap would not help). So the not starting is a different problem you're finding a coincidence.

 

So little update. We swapped out the water for coolant. Two days ago we took the car out for about an hour to do some stuff. The whole time the car ran great. Got home, turned it off, and car would not start again. After opening radiator cap a bit, pressure released and we left it alone. The next day the temp was a bit colder than it has been and the car would not start, to the point of almost killing the battery. It almost sounded as if it wasn't getting compression. Today we went to start the car for ***** and giggles and the car literally started right up no issues. However now the idle bumps up and down consistently and white steam/smoke can be seen escaping the radiator with the cap off. We took a couple of videos that I will upload soon. Is this still sounding like a cracked/warped head or block? Could these symptoms be due to the timing being off? It doesn't make sense to me how some days it runs perfectly and other days it won't even start.

 

i dunno why you opened the radiator cap after driving it...

 

If there is smoke / steam / coolant blowing out of the radiator when running cold with the cap off, there is definitely a leak inside the engine. There would be some steam when running hot with the cap off, but you should never try to open the radiator when hot.

And as I suggested earlier, the non-starting problem is probably unrelated to the cooling system.

 

I dont think water has anything to do with it, water or antifreeze, or mix, all the same results, just more corrosion with water possible..

 

I thought with straight water, it boils a lot faster which in turn would increase pressure in the cooling system. Of which the rad cap should release that pressure into the recovery bottle but if the cap is faulty?

 

Antifreeze does just that, prevents freezing. Water is the best heat exchanger, I've ran pure water for years with zero issues, in an area where it doesn't get below 40. I never heard if any differences in boiling.

 

Fluid - Freezing Point - Boiling Point

• Pure Water: 0 C / 32 F - 100 C / 212 F
• 50/50 mix of C2H6O2/Water: -37 C / -35 F - 106 C / 223 F
• 70/30 mix of C2H6O2/Water: -55 C / -67 F - 113 C / 235 F

It does raise the boiling point some. Coolant has a higher boiling point than water. As well, pressure also raises the boiling point.

It's also been mentioned that coolant has less thermal transfer properties than water. Water transfers heat better than coolant. I believe this is why the middle ground is typically chosen of 50/50 so you get the optimal of all properties, thermal transfer, boiling point and freezing point.

 

Hondas coolant boiling point is actually 265F degress.

edit: its 268F, just looked at the back of my container.

 

We were using a really diluted mixture of antifreeze and water. We got tired of buying new antifreeze so decided to just start using mostly water until we figured out the problem. Is there any chance maybe the intake manifold is leaking and excess air is being pulled into the system causing the build up of pressure we are seeing? It's definitely a build up of pressure, we can feel it in the hoses, and once the radiator cap is removed the pressure is released. We've tried two new radiator caps as well as the original. If it was a cracked head or block I feel like the car wouldn't run better than it did before. Before it barely ran at all. That and the car doesnt overheat at all.

 

intake manifold shouldn't have any affect with your cooling system. did you route the heater hoses correctly?

 

I’m having the same problems hope

 

did you ever find out the problem? I’m having the exact same issue.