05 Impala Coolant Issue

[AP Guy]

Alright, so I've been playing around with trying to troubleshoot my old daily driver that started to have some cooling issues. I started noticing the coolant gauge starting to move around and as time went on began to notice bubbling into the coolant overflow. That automatically made me think the head gasket finally blew. BUT, after running through a compression check all the cylinders came out ok. All were a bit low due to the mileage but all were within a few psi of each other.

I can idle the engine all day long and it seems to run just fine but as soon as load is put on the engine (ie: driving) it will overheat and coolant pressure feels crazy high and I can bleed the air out of it until I'm blue in the face to no avail so the coolant is getting air in it some way or another(boiling?) I did a coolant pressure check and I couldn't see any visible leaks, nor any noises or bubbling coming from inside the engine after pulling the plugs, opening the oil fill cap, putting my ear to the intake...nothing. I shut the air valve and pressure seemed to be holding as well. Oil is clean too.

I'm a bit stuck. Now my thoughts are potentially a failed water pump that's not circulating coolant? A failed thermostat?... even though a new one was installed with the LIM gaskets a while back that should fail open if it did happen to fail.

What am I missing?

 

[1987 GMC Jimmy]

I would do a chemical combustion gas test. You can borrow the tester at Autozone and buy yourself a bottle of the fluid for like $8.

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[hatzie]

A cooling system pressure tester will tell you right now whether you have combustion entering the cooling system via a blown head gasket or cracked block/head or just leaking via the 3.4L 3.8L favorite... blown intake gaskets. If the cooling system is pressurizing immediately it's likely leaking from one or more combustion chamber(s).
AutoZone used to loan these with a deposit. Horrible Fright sells cheap ones that will do the job too...

The Gen 7 and Gen 8 boards on the Impala Forums have more than a few old fart car guys that are willing to help out and the young'uns aren't too obnoxious. Generally a good mix. Kinda like here.

I have a Black 2009 Gen 8 LS4 V8 Impala SS and a Black 2004 Gen 7 Supercharged 3800 Impala SS. I like sleepers that look like cop cars on the highway. Which Gen 7 Impala do you have?

 

[AP Guy]

A cooling system pressure tester will tell you right now whether you have combustion entering the cooling system via a blown head gasket or cracked block/head or just leaking via the 3.4L 3.8L favorite... blown intake gaskets. If the cooling system is pressurizing immediately it's likely leaking from one or more combustion chamber(s).
AutoZone used to loan these with a deposit. Horrible Fright sells cheap ones that will do the job too...

The Gen 7 and Gen 8 boards on the Impala Forums have more than a few old fart car guys that are willing to help out and the young'uns aren't too obnoxious. Generally a good mix. Kinda like here.

I have a Black 2009 Gen 8 LS4 V8 Impala SS and a Black 2004 Gen 7 Supercharged 3800 Impala SS. I like sleepers that look like cop cars on the highway. Which Gen 7 Impala do you have?

I still kinda want an gen 7 SS supercharged impala, or an Indy 500 edition. A 96 SS is on my bucket list too, as well as a gen 8 impala or Monte SS. Not sure why but live always had either Monte Carlos or impala's as dailys. The 3.4 had their share of problems but generally once the LIM is replaced and it was caught in time they have proven to be just as reliable as the 3800. At least in my experience.

As for this bomber, it's just a base impala with the 3.4. It was my wife's car back when we were still dating. I think she bought it in 06/07 with 40k on it. It's got 240k on it now so I can't complain. I'm just debating if I want to put money into fixing it/ part it out/ or junk it. I've got a "new" daily now... another impala so this one is just sitting now.

I've been on the impala forums but most of my posts go nowhere on that board...? Not sure why.

I'm almost certain its a head gasket... but I'm not understanding why or how its holding coolant pressure and there's no leaks. But when I start it with the serp belt removed I'm getting coolant that's puking out of the radiator cap so that again points me to a head gasket. Never seen an engine pass a pressure check though unless there's some weird way it has a one way leak that's blowing combustion gas into the system but not allowing the coolant to flow back through the head gasket... just odd.

But, like I said I'm just tinkering with it now for my own curiosity. There's a lot of good parts on it yet so I'm debating on parting the thing out. Hate seeing cars get scrapped when there's good parts left and steel is in the dumps so I wouldn't get anything to scrap it out anyway.

Otherwise sell it to someone that wants to fix it. Or drop a junkyard engine in it.

 

[4WDKC]

just because its supposed to fail open doesnt me it will, what about a weak belt tensioner not applying enough pressure to keep the belt from slipping?

 

[AP Guy]

just because its supposed to fail open doesnt me it will, what about a weak belt tensioner not applying enough pressure to keep the belt from slipping?

Can see the pump spinning with the belt on. I think I cam rule out the thermostat. I believe it's opening since I can get coolant to bleed through the thermostat housing and there'd only be coolant flowing there with the t stat open. Coolant out hose is also hot.

 

[hatzie]

Do some detective work.
A quick N dirty way to find your leak is to blow shop air into each cylinder with the piston on that cylinder at TDC and then BDC.
An "Air hold adapter" is around $10. It screws into the spark plug hole and allows you to connect your shop air hose to the cylinder. I usually add a ball valve between the shop air hose and the air hold adapter.
To find TDC and BDC I pull the rocker covers and spark plugs. A dowel will let you see how far down the piston is and you can watch the valves actually close with the rocker cover off.

If it leaks at TDC it's generally a cracked head or head gasket issue.

No leaks at TDC and leaking at BDC points to a cracked block.

This will let you handicap the condition of the valves and how much blowby you're getting into the crankcase too.
Pull the intake hose and listen for air leaking through an intake valve.
Listen at the exhaust for air blowing past the exhaust valve.
If you can... listen for air blowing into the crankcase.

 

[4WDKC]

Can see the pump spinning with the belt on. I think I cam rule out the thermostat. I believe it's opening since I can get coolant to bleed through the thermostat housing and there'd only be coolant flowing there with the t stat open. Coolant out hose is also hot.

ever watch how much the tensioner moves when revving an engine ... try it sometime. how old is the water pump? Maybe the fins have deteriorated in the pump and it cant move enough coolant? How old is radiator maybe its just plugged full of gunk and can transfer enough heat while driving to cool the engine.

 

[AP Guy]

Do some detective work.
A quick N dirty way to find your leak is to blow shop air into each cylinder with the piston on that cylinder at TDC and then BDC.
An "Air hold adapter" is around $10. It screws into the spark plug hole and allows you to connect your shop air hose to the cylinder. I usually add a ball valve between the shop air hose and the air hold adapter.
To find TDC and BDC I pull the rocker covers and spark plugs. A dowel will let you see how far down the piston is and you can watch the valves actually close with the rocker cover off.

If it leaks at TDC it's generally a cracked head or head gasket issue.

No leaks at TDC and leaking at BDC points to a cracked block.

This will let you handicap the condition of the valves and how much blowby you're getting into the crankcase too.
Pull the intake hose and listen for air leaking through an intake valve.
Listen at the exhaust for air blowing past the exhaust valve.
If you can... listen for air blowing into the crankcase.

A leakdown check was my next step to isolate if it's a head issue or a block issue. But either one should still show itself during a coolant pressure check wouldn't it? Guess I could try a pressure check when the engine is warm. Maybe once everything expands something will show up.

Also I should note when it sits and cools down... say overnight or a week(however long it is until I get back around to it) and I pull the cap off there's still pressure in the system. Not tons but enough to burp some coolant out of the filler neck. So that just reaffirms it can hold coolant pressure. But why isn't all the pressure being released as it cools and brings in the coolant from the reservior. Radiator cap is brand new. Due to it being over-pressurized?

ever watch how much the tensioner moves when revving an engine ... try it sometime. how old is the water pump? Maybe the fins have deteriorated in the pump and it cant move enough coolant? How old is radiator maybe its just plugged full of gunk and can transfer enough heat while driving to cool the engine.

The tensioner has plenty of spring yet. I've seen what a belt looks like at speed but generally tightens up around The pulleys as long as the tensioner is doing its job. The water pump was changed out close to a year ago... not saying it couldn't be bad but there's no signs of leaks at the weep hole unless the impeller somehow sheared off the shaft bit the pulley on the pump is still rigid

I might play around with it yet this weekend if I have time. Losing interest but if I sell it I'd like to tell the future buyer I've pinpointed what's wrong. I might be caring too much lol

 

[AP Guy]

I'll also start it with my tester still installed. If there's a head gasket leaking I should see pulses on the pressure gauge. That should give me everything I need to know

 

[hatzie]

If you don't see pulses on the gauge with the engine running you have an old-fashioned overheat issue. These V6 engines heat up pretty quickly.

If it's a garden variety overheat problem I'd check that the water pump still has an impeller and not just a stub where the impeller fins used to be. If it's the water pump I'd swap the thermostat at the same time with a new Stant Super Stat. The Stant Super Stat fails open rather than closed... cheap insurance.

 

[AP Guy]

Well I played around with it a bit today. Pulled the water pump off and it was fine. Impeller and bearing in good shape. For kicks I started it for second just to watch the coolant and sure enough it rose from out of the block and started pushing up out of the water pump cavity. So... I'm completely stumped as to why it can hold pressure yet is pumping air into the system but I think I'm done with it. I've got too many other projects to do lol.

Going to wash my hands of it and part ways. After topping it back off and letting it idle for 10-15 minutes temp gauge was just over 1/2 way and bouncing up to 3/4 way up the gauge. Probably in the 210-240 range. No fluctuating in the pressure gauge but pressure was slightly rising to about 20psi by the time I shut it down. Not a steep rise in pressure but was a fairly constant rise as it was running... which is normal but at that pressure it would be tripping the pressure cap anyway

It had a good life

 

[Honky Kong jr]

Could be air bound.....( have an air pocket, blocking coolant flow)

 

[hatzie]

The 3.1L & 3.4L have a cooling system that makes em trap and hold onto air.

The LS4 5.3L V8 and the 3.5L 3.6L & 3.9L V6 aren't much better.

You need to bleed her out.

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[AP Guy]

The 3.1L & 3.4L have a cooling system that makes em trap and hold onto air.

The LS4 5.3L V8 and the 3.5L 3.6L & 3.9L V6 aren't much better.

You need to bleed her out.

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I've bled and bled and bled this system, only to get more and more air trapped in it. This is my 4th 3.1/3.4 and I've never had an issue getting the air out although that water bottle idea looks pretty slick. It does take a bit but I've always been able to bleed them out ok. The system was never opened up to get air in it so something changed to let the air in. Started with hearing sloshing in my heater core under acceleration, then temperature gauge movement, to what it is now, not able to drive it without it red-lining.

In the past I'd leave the radiator cap open and bleed it/fill the radiator once the thermostat opens but I can't do that since it's pushing the coolant up out of the cap. There shouldn't be much movement in the coolant at all when the tstat is closed. Maybe a bit from the water pump spinning straight inline to the inlet side of the radiator, and maybe some rise from thermal expansion but not enough to gush out the cap, with or without the serpentine belt on to spin the pump.

I'll play around with it more today if I have time...or feel like it