Small Issue, Need some more experienced help. Options

[bsamps4]

The good: Car starts up and and warms up, and drives great.

The bad: when under load the temp gauge lowers about 1/8th of an inch under heavy boost. I'm only running around 7psi for break in. I also have a tiny coolant leak, very tiny. and a low temp thermostat from ATS. after a few seconds of driving normaly (no boost) the car begins to creep back to normal temp, and it will remain there. Even at a stop light. So I don't know if this leak under boost is causing the temp gauge to read incorrectly. Perhaps an air bubble created from the leak is causing this?

Just need some thoughts from you guys. Any advice would be appreciated.

Issue #2:

When the car is at idle it's reading around 15 vacuum, I'm under the impression that this should be more what 21. From time to time the car will idle around 1100, and when it does the vacuum is at around 20. The idle will drop to about 600 when the car reads 21.

Scenario: I stop at stop light car idles at 1100-1200 with vacuum at -20. After about 30 seconds car sputters slightly, and vacuum raises to -15 and idle drops to 600ish.

WHAT'S THE DEAL WITH THIS!!!

[batcavee00]

For the temp issue, I wouldnt worry much, unless its overheating. Maybe the sensor is faulty...for the vacuum issue, double check for vacuum leaks. I had a similar issue, I had a crack on a vaccum hose behind the manifold. I used starting fluid to find it. Replaced hose, now my vac is around 22-25. You might want to clean ur iacv..Hope it helps

[Smaay]

improper temps will make the ECU fuel differently. check the thermostat. sounds like its not closing properly

[bsamps4]

I may just buy the factory thermostat. The one I have now is supposed to run 10 degrees cooler.

[Smaay]

10 degrees shouldnt make that much of a difference. im wondering if its sticking wide open

[bsamps4]

I certainly hope not. It's a brand new thermostat. That's not to say it couldn't be defective, but I've had a bad thermostat before that was frozen open, and the car would never make it to operating temperature. I've tracked my coolant leak to the top radiator hose where it connects to the water neck that houses the coolant temperature sensor. It only leaks during heavy load (5th gear boost pull), and it is during these heavy load pulls that my temp sensor starts to react. I'm thinking i'm getting air into the system which could be causing a mis-read in engine temp. What are your thoughts on this theory?

Also it seems like it's not boosting as hard. I'm thinking my vacuum leak may be getting worse. How would you use starting fluid to locate the leak?

I had another theory about this....I'm using the stock BOV, and I'm venting it atmospherically. This may be resulting in a leak if it's not getting vacuum to where it used to connect to the air box....perhaps it's not shutting all the way due to this...???

[Smaay]

that would be an issue on a MAF car. but since we are a MAP, the open atmosphere is not a problem. im more worried that while you are boosting you are getting a leak at the head gasket and pressurizing the cooling system. that will cause your problems. have you ever had teh head off? maybe its time to replace teh stock gasket with a MLS gasket. Toyota upgraded teh gasket in 98. so if you get a new one it will be MLS

[batcavee00]

With car iddling,...spray starting fluid around vacuum hoses, around and behing manifold. Dont forget to spray around the injectors cause sometimes those gaskets suck in air from there. If u have a leak, your card idle is go gonna sound different if it sucks in starting fluid. Thats how u find leaks. Buy 2 bottles cause it runs out fast lol

[bsamps4]

that would be an issue on a MAF car. but since we are a MAP, the open atmosphere is not a problem. im more worried that while you are boosting you are getting a leak at the head gasket and pressurizing the cooling system. that will cause your problems. have you ever had teh head off? maybe its time to replace teh stock gasket with a MLS gasket. Toyota upgraded teh gasket in 98. so if you get a new one it will be MLS

I completely rebuilt the motor. The head gasket is MLS and is bolted on with ARP studs.

[bsamps4]

Smaay, would a blown head gasket result in my vacuum fluctuating slightly?

This post has been edited by bsamps4: Mar 21, 2012 - 6:55 PM

[bsamps4]

I ran a test tonight after work. I warmed the car up all the way and gave it a couple of non-boost revs...only to around 2500. I squeezed the top coolant hose before and after and it felt the same. I then boosted across the parking lot (temp gauge fluctuated), parked the car and checked again. After I boosted I felt the hose and it was really tight. I also noticed that a little coolant had leaked right at the water neck.

The odd thing is that after the heavy boost the car idled at 1500 and backed back down to 700-500. The vacuum during this time period moved from 21 down to 15. When it hit 15 the car was idling at 500ish.

[bsamps4]

coolant does NOT smell like gas.

[bsamps4]

Test #2 completed. I started car with radiator cap off. Car was cold at the time. No coolant shot out. Revved motor to 2psi at full throttle to 4k...no coolant shot out....becoming more skeptical of the blown head gasket issue. Is it possible that I just poorly burped the cooling system?

[ricochet1490]

That really is odd. are you concerned about pulling coolant into the cylinders via a bad head gasket?

[bsamps4]

Yes possibly. I just did a compression check and all four cylinders are at 140 Psi.

[ricochet1490]

my experience with blown head gaskets is minimal at best, but I believe you'd be able to smell it... possibly this is what you meant when you said coolant does NOT smell like gas.

If you are loosing coolant but none of it is ending up on the ground, one must consider the possibility that it's being burnt. But making sure it's being burnt inside the cylinders and not say, dripping onto the exhaust headers for instance is going to be the challenge. If you aren't loosing coolant, then it could just be a bad burp of the system.
The most intriguing thing for me is the fact that it happens while under heavy boost? And how that whole thing effects your vacuum....

Something to think about because I admittedly am unsure of the full working mechanics of the coolant in relation to the vacuum and your hoses is this.
Any fluid with increased traveling velocity has a decrease in pressure in comparison to its slower moving counter part. This is a simple concept of Bernoulli's equation and is generally applied to pipe flow with different diameters and an incompressible fluid, a perfect assumption for a motor with many different diameters of pipe.
So when you really lay into the throttle, and the water pump starts putting more and more pressure on the coolant system to move a larger volume of water through the engine in a given time, the faster that fluid moves.

I have no idea if that bit of information helps you find what you are looking for, but if there was an air bubble in the system, that kind of velocity and vacuum would certainly compress the air bubble and change the internal characteristics of the pressure of the system in my mind.

Oh and 5s block or 3s block?

[ricochet1490]

Yes possibly. I just did a compression check and all four cylinders are at 140 Psi.

given that the head gasket is part of the compression check, does this rule it out?

[easternpiro1]

this may be far off but i am having the SAME issue as far as the idling goes... im at 15-17 vac when car is idling (after driving it a bit) but when im at a light my idle will go down to 700.

what i found wrong was actually the throttle adjustment... after i adjusted the cable (and added a helper spring) it idled fine! (it still does it from time to time, but only when car is cold...

try to take a look at your throttle cable position, try to tighten it a bit

[bsamps4]

My Rad fans aren't coming on. This explains a lot!

[easternpiro1]

what was wrong? not plugged in? sensor didnt trip? what fans do you have? and will you be running them the whole time?




This post has been edited by easternpiro1: Mar 23, 2012 - 8:55 AM