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By cirrus, March 2, 2014

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It's normal for coolant pressure to rise and fall when the engine is revved because the water pump is moving it around faster or slower.

I was wondering if the pump could cause that....but also I wondered its a closed if the pump pushes the also needs to pull the would the coolant rise and fall just from that? I was going to hook the pressure tester up to the Corolla and see if that does the same but I've been wiped out with this cold virus.

It hasn't been using any large amounts of coolant....over a week the level in the overflow has stayed the if it is a gasket leak it must be very tiny.

Pressure will change with increases and decreases in coolant temperature, trapped air bubble will do that as well. Fluid flow from the waterpump is not strong enough to cause the pressure to change like that. You also have changes in engine dimensions (thermal expansion/contraction) that will also affect pressure readings.

If you didn't see coolant gush out or pressure spike when you raced the engine - you don't have a headgasket leak. Your Honda is acting like some BMWs that I've worked on - some have to be bleed 5-6 times, as air is hard to get out of their system.

Possible that you've finally gotten the original trapped air bubble out of the system - keeping the coolant reservoir tank filled maintained a full radiator and it is siphoning extra coolant as needed. That or you've circulated a possible obstruction out of the heater core and/or your water pump automagically fixed itself.

When I did the dynamic test the motor was cold....and it was only running for like 10 seconds when I saw on the gauge it pop up about 1psi. Then right away I pressurized it to 13psi and rev'd the motor up and down and I saw that 1psi fluctuation. The motor was still cold. From what the tester booklet said....if the gasket was bad the needle be jumping around like crazy.

Something seems odd with the whole when I was doing the static pressure test and at the end of the test you let out the air pressure via the hand held blew back into the tester the coolant so it was running out of the hand held pump/gauge....and when I took off the radiator test cap the coolant was right to the top of the filler neck.

Like there is a big air bubble trapped in there and I pressurized it with 13psi...then released it that trapped air pushed back the coolant. I don't know....grasping at straws here.

I just want to eliminate the head gasket as best I can....its still doing the heater issue so then its either the pump impellers wore out or the heater core clogged which I find hard to believe too. But we can live with that issue esp with summer coming on.

But if its the gasket then I'd get it fixed before it really gets bad and warps the head...ect.

Yeah, I understand where you are coming from. As for the coolant nearly overflowing the filler neck. On level ground, with a full system - that is exactly what it is supposed to do. On all my cars, if I popped the radiator cap, the coolant will be right at the neck, spilling out a bit.

From what you described - doesn't sound like a leaking head gasket - at least not right now. Even a tiny pinhole leak will cause the pressure to fluctuate wildly.

It doesn't sound like a gasket either though I've seen a few posts claiming they've done the same tests as I have and they were fine...yet it was the gasket. BUT....I tried to point out that they also changed water who really knows what the issue was.

For sure something is causing the upper heater core hose to be a lot warmer than the bottom(exit) hose. I don't think that's normal. A coworker as the same exact car...I should check his. Either mine does a have a heater core blockage of some sort or the water pump is really weak knee'd. A lot of Honda guys told me they back flushed the heater core and crap does come out. But man getting at those hoses is not easy on that car...almost need to take the head off!

Well for now I'll keep a close eye on it. We haven't had a day over 50F in months so right now the cold air is not hurting it...but when it hits 70F see if it starts boiling over...ect.

We still don't know what car to trade in....for sure one has to go this year. The Honda has 25K less miles then the 2005 Rolla but isn't aging well....its well known for having autotranny issues....and its had like 10 recalls the past 2 years which has led to a host of panels broke thanks the ham fisted dealer techs. I got nowhere trying to get them to replace them....their RTV trick was cute. Also the CD player stopped playing home burned CD's.

EDIT: just talked with the company that made the pressure tester. They said what I'm seeing is normal and doesn't like a gasket issue....that even the 1psi in 4 minutes is excellent as that unit would leak a tiny bit over 4 minutes at that pressure.

Thanks for all the help Fish(and biiter)....I gave it my best shot in diagnosing it...see how it goes the next few months.

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