Well I posted not to long ago that I smelled coolant when driving my car, but could NEVER find a leak. I bypassed the heater core, still smelled, cleaned off the engine thinking it was old coolant....still smelled.......****Well after looking and looking and looking I happened to take off my radiator cap to check the fluid level thinking it had to be running low with the coolant i smell but could never find. After inspecting hte radiator capand noticing the rubber seal was deteriorating I started looking around the radiator cap AREA and noticed coolant spray stains on random spots.

Well apparently the caps seal was no good but only under hard acceleration would the pressure build high enough to spray out of the cap and start smellling.

So if u have a mysterious smell and cant find a leak, check the radiator cap

 

i fail to realize how in refilling your coolant after the heater core bypass, you managed to look over that.... i mean i guess i can see it happening, but in proper maintenence of cooling systems, i guess for me its just second nature, i always check out the little stuff... cuz they always cause big problems!

 

oh, the other thing... your car never overheated with a bad rad cap? it would seem to me that the loss of pressure would cause the car to overheat... JMO...

 

A bad cap seal wont cause the car to overheat directly, true it will because it will allow coolant to escape. On my old CJ I could leave the cap off and it would be fine. The only reason coolant boils over if you pull the cap while its hot is because of the pressure. Thats a common misconception, its not because the waters hot that it blows out all over the place (true thermal expansion to some degree) its the pressure created by the hot water that forces everything out. Kinda like shaking up a soda (pop for you Ohio folk ) the pressure makes it explode not the temp of the liquid. I could run my CJ all day with the cap off and it wouldn't overheat. Another interesting tid bit, the cap not only controls the flow to and from the reservoir, its pressure rating also helps control the boiling point of the coolant. I forget if its more pressure = higher boiling point or vise versa. Also learned that with a CJ, couldn't figure out why it kept overheating, finally changed to a different PSI cap and it never did again.

 

"I forget if its more pressure = higher boiling point or vise versa."

Yes, it's more pressure = higher boiling point, and is one reason caps[cooling systems] are 'pressurized' to begin with..

 

ok help me figure this one out,i also get a coolant smell,no signs of leaks inside or out,my mechanic says because the headers are so close to the heater box and hoses thats what causes it,has anybody else have this happen?Mostly in stop and go driving can you smell it not at highway speeds,car does not run hotter than 170.

 

I've got the SLP shorties too. I ran without the heat shield on the passenger side for 20min, and the plastic on the heater box started to melt. They definitely get hot over there. I'm gonna check my radiator cap. I know it's old. I can't believe I didn't think to check it.

 

Water boils at 212. a 50/50 mixture boils at about 230 in normal atmosphereic pressure. the boing point is raised approx 3 degrees for every PSI applied to the surface. My coolant is always between 165 and 180 so mine would never boil over, although it may overflow due to expansion...

 

Well heres an update, After buying my new radiator cap and going to install it I checked a little harder and the 2nd hose under the cap was what was leaking. It was the small hose under the coolant overflow return hose. I have this hose bypassed, I think it went to the throttlebody origionally or something. Anyhow THIS was the cause of the leak, not the cap. The cap was just in crappy shape and it was possible it was leaking too. As far as overheating I love how SOME people are so quick to say IM LYING or something. MY car never overheated, hence why I couldnt figure out WTF the smell was coming from.

ZeeDub, Your cam is small, do you check it daily ?

 

didnt know there was a heat shield on the heater box,need to double check or i can fab something up.

 

There isn't one. My headers came with a sheet of Aluminized fiberglass weave to put on the passenger side. That's what I was referring to.