Boiling in Upper Rad Hose

[robeats91t]

Hey guys, I've been lurking here for awhile and can't find a direct answer to a situation i'm encountering. When I shut off the car, I can hear coolant boiling in the upper radiator hose, and the hose itself never feels firm. And yesterday morning I found a coolant spot on the driveway, coming from somewhere around the water hose below the CPS.

The thing that has me nervous about this is the stock temp gauge stays rock solid just below halfway, and my greddy gauge will read between 85*-105*C and never move any higher. The greddy temp sensor is mounted where the bvsv used to be, if it matters. My heater vsv gave up the ghost, so to test for air in the coolant I have the vacuum valve held open, and I have constant heat with no air pockets. I've burped the system repeatedly, and I replaced the stock mech fan & clutch with a dual flex-a-lite setup--initially, I had it wired up to come on with the ignition, but changed it to come on when the a/c fans would have come on (which usually makes the fans kick on at about 103*-105*C) and the resulting coolant temps are nearly identical to the always-on fan setup so far. Last night in about 12*C (55*F) temps the fan came on once at a stoplight, and once again when I parked it before the turbotimer time elapsed. Both times the fans stayed on for about 10 seconds until temps came back down below 100*C. Everything feels great, seems to be staying cool, but I usually feel that with this car, when nothing's wrong, something's wrong.

Everything seems fine, the car drives great, but something's obviously wrong. Anyone have any ideas?

I'm mainly worried that I'm doing damage that is not yet apparent. I'm going to go get a replacement for that potentially leaky hose, but after that...I'm out of ideas--I'll have all new hoses at that point, and I'm not sure what else to check.

I just finished a hg job on my engine, my first one ever, 2nd one on the car since I've owned it, so I'm really nervous about everything going ok.

Here's what was done in the hg job:

Toyota hg on resurfaced head
ARP bolts tightened to 90ft/lbs
egr blocked off
isc/tb water hoses eliminated
new Toyota radiator hoses
new Toyota turbo water hoses
new Toyota heater hoses
new Toyota t-stat & rad cap
Toyota water pump, oem-style radiator 25k old
new Champion platinum plugs

Any help would be greatly appreciated!

 

[mrnickleye]

The bubbling in the upper hose (mine did it before the bhg repair) happens from air in the system. Air rises to the highest place in the system.
When you shut off the engine, and the coolant flow stops, there are hot spots due to some air in there. The coolant hits them and boils, creating the bubbling.

Fix the leak, which can allow air into the system as the engine cools down.

Normally, a little coolant gets pushed into the overflow bottle as the engine is heated while driving. During the cool-down, the engine sucks that coolant back in.
If you have a tiny opening (leak) in the system (including the hose to the bottle), air will be drawn back in instead of coolant.

 

[robeats91t]

I'm thinking it must be that 90* hose below the cps or maybe even the o-ring around the green temp sensor on the t-stat housing (which I didn't get when I got the new sensor). I don't think it's the hose to the overflow tank; it's new silicone, as is the hose inside the overflow tank. Thanks for the input though--it's definitely air getting in somehow...

I drove it around for a few hours today, and the temp was very consistent--from 90* to 105* C, in 24* to 27* C ambient temps. The overflow bottle ended up filling up within the first 30 mins, however. It then dribbled out a little bit, not sure how much, as I don't have an overflow bottle for the overflow bottle, just judging by the small amount of coolant on the intercooler. I'll check the rad tomorrow when it's cool to see how low it is.

Looks like I'm off to the stealership again tomorrow...

Thanks for the help, mrnickleye

 

[SPD TRP]

I'm thinking it must be that 90* hose below the cps or maybe even the o-ring around the green temp sensor on the t-stat housing (which I didn't get when I got the new sensor). I don't think it's the hose to the overflow tank; it's new silicone, as is the hose inside the overflow tank. Thanks for the input though--it's definitely air getting in somehow...

I drove it around for a few hours today, and the temp was very consistent--from 90* to 105* C, in 24* to 27* C ambient temps. The overflow bottle ended up filling up within the first 30 mins, however. It then dribbled out a little bit, not sure how much, as I don't have an overflow bottle for the overflow bottle, just judging by the small amount of coolant on the intercooler. I'll check the rad tomorrow when it's cool to see how low it is.

Looks like I'm off to the stealership again tomorrow...

Thanks for the help, mrnickleye

I hate to be the bearer of bad news, as mine did the same thing, never overheated at first, only pushed coolant out of the overflow all over the intercooler. I was in HG denial, replaced the thermostat, cap, fan clutch, and radiator with new parts. Still the coolant push out. Finally I went to a shop and had the exhaust gas in the cooling system test. All they do is start your car and put this jar over the radiator opening (where the cap goes) that has this indicator fluid in it, they then use this bulb to prompt some of the air in the coolant system through the indicator fluid, if it changes color, then you have exhaust gasses in your cooling system, in my case it was a blown headgasket.

You can buy one of these kits for around $40.00 at Napa I believe.

Oh yeah, I said it never overheated at first, well in denial, before the test, the entervals for adding water became shorter and shorter as it would push so much out of the overflow.

This was my story, hopefully yours will have a different ending. After I changed the HG, with a new cooling system, my car runs cool with the AC blowing cold in these South Texas summers.

Good luck

Wayne

 

[robeats91t]

Wayne, as much as I don't want to hear that kind of possibility, I must take it into consideration. As this is my 2nd HG repair in the 5 years I've owned the car , (the 2nd within 20k miles of the first) I live in constant fear of "the next one." The thing is, though, I've driven it less than 500 miles since this last HG job...

I went out and checked on things this morning, the overflow tank was at a normal level (between the two marks on the side) but I noticed that squeezing the upper rad hose sent coolant into the overflow tank--very little squeezing effort...is this normal? Seems like a bad radiator cap...it's a new Toyota rad cap on a CSF oem-style radiator. Should I try to find a CSF rad cap? I didn't think it'd matter? :dunno:

Is the radiator cap supposed to give way so easily when the upper radiator hose is squeezed? I wish I had a rad cap tester...

 

[mrnickleye]

I know caps, its my job to. Pull your cap off and hold it up like its on the radiator. There is is little valve on the very bottom. On our cars, the valve is suppose to have a small spring to hold it snug against the black rubber seal.

Many caps (for different cars) of the same size don't use the spring, thus the little valve is loose on the cap. It will hang down a tiny bit. Check this valve with your finger nail. If it does not stay against the seal(no spring), then its the wrong cap.

A Stant cap at any parts house is about $6. 13lbs. not 16.

The "dangle" cap, as I call it, was designed for several different vehicles, including my Chevy crewcab truck. It allows some coolant to flow into the bottle as it slowly heats up. This effectively relieves some of the pressure buildup on the system as it gets hotter. Coolant flows back and forth everytime the engine heats and cools.

I thought about putting one on my supra, but decided against it.

PS. a shop did it, and my HG lasted 3 years. They left vacuum lines off and probably did a "quicky" without sending the head out to the machine shop. I did it this time, with valve job and resurface.

 

[robeats91t]

mrnickleye,

I pulled off the rad cap, and it's definitely got some dangle going on. Also, through some crude measurements, I discovered that the spring-loaded seal that seals the radiator closed does not seem to actually touch the inner surface of the radiator, allowing free flow between the radiator and the overflow tank. This isn't normal, is it? I really think I have the wrong cap; I know this Toyota cap did not come with this radiator. I'm going to go get a new one right now and see if it's any different.

 

[mrnickleye]

Right !! Many newer cars (toyotas too) have a 'shallow' cap. You need the 'deep' one. They are small diameter (not big like a chevy, ford, etc), and look the same, except if you look close, the one you need is taller/deeper, to seal on the radiator. Its only about a 1/2" difference.

 

[mkIIIman089]

I actually ordered a new OEM radiator when my PWR went bust a little while back and it had the "dangly" cap mounted on it when I got it. And like it has been stated before the dingly cap is not even close to the same dimensions of the sprung one, and wouldn't seal causing the problem you are seeing.

 

[robeats91t]

Good news!

In Stant's application guide, the "deep" cap is listed for the 7mge and the "shallow" cap is listed for the 7mgte--brought the "deep" cap home, popped it on and before starting it I noticed the upper rad hose was much firmer. Warmed her up and the temp stabilized at 81*C, and the heat works in the cabin. After shutoff, viola! No more boiling!!

Thanks guys for all your help!

 

[GreenChevelleSS]

Damn I went to autozone and bought a new cap and it the shallow "dangly" cap too guess im gonna have to take it back. My problems been boiling in the overflow bottle and spraying out on the intercooler alot when the bottles not even full....