Sucking air???

Me again...
Just for yucks I pulled the BobG radiator and put the OEM uni back in. While the OEM radiator and fan still work real well, I'm still getting air in the system.

The air enters WHILE I'm driving and not after a cooling cycle. I cannot find any coolant leaks or drips under the car ever. Haven't pressure tested recently but did when first encountering this issue over a year ago and the system held. When I swapped the radiator, I drained the coolant and no oil/crud in it -- was very clean.

Hussein: Can you show me where the vent is located on the water pump? Diagram or photo would be helpful. I'd like to plug mine and see if that solves the problem. If not, I'll probably try the UV dye test...

lookforjoe said:
There is also a vent/valve in the underside of the water pump (on my AC equipped version). I know this, 'cos when using Evans Waterless it has to be filled with silicone to prevent air being sucked in....
Click to expand...
 
I have a spare pump in the basement - I'll take a pic tomorrow . I looked through my serp. belt mod thread, but couldn't find any pics of it.
 
Hole in the water pump is a drain hole, designed so that if your water pump seal fails, water can find a way out and away from the bearings... so you'll notice it before the bearings seize... if plugging the hole fixes the problem, it would be time to replace the water pump as the seal would be suspect.

I have seen pin holes in the metal pipes under the car that would only weep one or two drops out, but draw air in on cool down...

When you replaced the head gasket did you check the block and head with a good quality straight edge?

Does the bleed screw at the top of the radiator have a copper washer to help it seal? Do the two drain points in the steel water pipes have a copper washer to help them seal? (both these points have a copper washer from the factory)

SteveC
 
Greg, I always got air ...

Nature of the beast. Every once in a while, you have to bleed the radiator.
The coolant tank generates tiny air bubbles when the engine runs.
The return coolant line splashes air into the coolant tank by design. Even though coolant draw is out of the bottom of the tank,
small air bubbles do accumulate over time.

You can minimize this by keeping your tank 5/8 to 3/4 (max) full.
 
Bob and Steve -- thanks for your questions and recommendations!
- When I replaced the head, I checked the block with a straight edge and also cleaned it up. However, the prior gasket I removed also looked good and I had the same problem with it installed :(
- I was using a copper washer on the radiator bleed screw. I'm now using a fiber washer from MWB. Doesn't seem to make a difference.
- I can accept some air getting into the sytem, but I get quite a bit. Probably 1-2 seconds of hissing when I relieve the bleed before fluid squirts out. Odd, but I think once it fills up that much I don't seem to get much more air.

I rented a pressure tester again today, and pressurized the system to 18 psi. I couldn't find any drips, leaks, etc after letting it sit for an hour. However, the PSI did drop to just over 17 after sitting for a little over an hour. Checked the exhaust closely when I removed the pressure tester and re-started -- didn't see any white smoke etc. from the exhaust.

The X isn't overheating. Steady as a rock at 190 when moving. But after a hard run and idling or in stop and go traffic, the temp guage will rise a few ticks over 190 and stay there until I get moving again. Front fan comes on when needed but starts a little sooner when there is no air in the system.

I'm now wondering if I have a small crack or gap somwhere where a very small amt of exhaust can inject some air bubbles into the system. However, they'd have to travel thru the thermostat, under the car, and bubble-up to the top of the radiator. I dunno -- this one's a real mystery.
 
pressure test hot or cold?

Very hot works best as a diagnostic as that replicates the running conditions...be careful removing the cap,or run to temp with cap off, then put pressure tester on and pump it up, running the car and report what happens.

I've seen cooling issues from things as simple as the wrong radiator caps... I like the genuine IPRA ones myself, probably about three times the cost of aftermarket, but they last a long time.

SteveC
 
Was tested cold but will test again hot. Using a new (less than 2 yrs old) stant overflow cap -- the same used by several folks here).
fiatfactory said:
pressure test hot or cold?

Very hot works best as a diagnostic as that replicates the running conditions...be careful removing the cap,or run to temp with cap off, then put pressure tester on and pump it up, running the car and report what happens.

I've seen cooling issues from things as simple as the wrong radiator caps... I like the genuine IPRA ones myself, probably about three times the cost of aftermarket, but they last a long time.

SteveC
Click to expand...
 
Maybe not with 18psi though... pretty sure the X19 runs a 0.75 or 0.8 atm cap... so use about 12psi hot.

SteveC
 
I over-pressurized at 18 psi with the intent of forcing a leak if there was something marginal at the std 11 or 13 PSI cap used.

But even at 18 PSI I didn't find anything.
 
overheating

remember that a small pinhole, yes from a pin, tends to let the water escape as steam, and won't leave a trace of water. and as the water cools this "pin" hole will draw air in as the water cools and contracts.
it might be that the leak is in the enclosed tubes in the tunnel, where you might not even notice.
maybe a stethoscope is in order to listen for a hiss under the car at strategic point, or possibly a few well placed weep holes in the tube tunnel to check for leaks and to hear it better. the ones on the red demon were rotted through and I had a couple of stainless tubes bent and replaced them, and the holes in them were "pin" holes and didn't see them at all. I found them when I was installing the floorboard and wanted to put in cross supports for the seats. worth a try??
mikemo
 
geekdaddy said:
- I can accept some air getting into the sytem, but I get quite a bit. Probably 1-2 seconds of hissing when I relieve the bleed before fluid squirts out. Odd, but I think once it fills up that much I don't seem to get much more air.

Checked the exhaust closely when I removed the pressure tester and re-started -- didn't see any white smoke etc. from the exhaust.

The X isn't overheating. Steady as a rock at 190 when moving. But after a hard run and idling or in stop and go traffic, the temp guage will rise a few ticks over 190 and stay there until I get moving again. Front fan comes on when needed but starts a little sooner when there is no air in the system.

I'm now wondering if I have a small crack or gap somwhere where a very small amt of exhaust can inject some air bubbles into the system. However, they'd have to travel thru the thermostat, under the car, and bubble-up to the top of the radiator.
Click to expand...

Air will dissolve in the water quite well when it's hot and circulating... it will come out of suspension as the water cools and find it's way to the highest point, those being the top of the radiator,and the header tank. You won't find the air in the header (unless you have a large build up of pressure when running) but it sure will collect at the top of the radiator.

The white smoke thing from the exhaust is a bit of a myth,I've been mechanicing for 35 years and the only place I have ever heard it mentioned is on internet forums. Ethylene glycol (the most commonly used antifreeze/ coolant additive) has quite a low flash point once you separate it from the water it's mixed with, so will flash and burn in the cylinder. It produces quite a distinct odour when it flashes (burns) but does not produce white smoke. The white smoke people talk about can only be water vapour, and the chemical reaction of burning fuel (benzene) produces water, at the rate of 1 litre of water per 1 litre of benzene, which comes out as water vapour...seen as steam on cold mornings and drips from the tailpipe as condensate, all perfectly normal for a benzene driven internal combustion engine.

If your fishing for a cracked cylinder head...and your not overheating...I would very much doubt it. There certainly are EGR passages in the exhaust ports that can come very close to the water passages internally... but the most common place for them to intersect is at the thermostat housing gasket, but that is now such a well known trap for young players that I hope you haven't been caught with this one...

SteveC
 
Has it been solved, that is the question?

Well, I have exactly the same issue won't get it sorted out. What did you do to get rid of the air in the radiator?
 
I don't know... yet...

This winter I replaced the water pump and water pipe and re-routed the heater hoses. Freshened the gaskets etc. Not clear to me that this will fix the problem but I wanted to re-route the heater hoses anyhow (they were close to the allison's header) and I'm hoping they had something to do with the air intrusion as well.

FInishing up my interior re-do and will hopefully have her back on the road in less than two weeks. Keeping my finger's crossed...
 
my

:2c:
did you bleed the cooling system with the nose of the car as high as you could get it??
air always climbs to the top. and make sure the heater valve is open to purge any air is removed from that circuit also.
had a similar problem in my Camaro turned out to be a small pinhole in one of the hoses. pressure up, steam escapes, pinhole closes and no sign of water anywhere. hope this is helpful.
mikemo
 
The saga continues

Well after ~150 miles I can attest that the problem still exists after re-routing my heater hoses and swapping the water pump. With the aluminum radiator it's difficult to know it's filling with air because it's so darn efficient. But I eventually find my radiator cooling fans start coming-on later than they should at some point. The car is still very driveable and even with the air it never gets into the red zone of my temp gauge but it's something that's clearly "not right" and I'd like to fix it. Would make me feel more comfortable with longer trips and stop-and-go traffic situations in the summer heat.

It's gotta be related to my head gasket or block. But the old head and gasket did the same and I don't detect any exhaust gases nor oil in my coolant. Not seeing any significant pressure losses in the coolant system and the cylinders are also holding pressure well. In a prior conversation with Matt he also found it odd that the air was accumulating in the radiator vs the water pump or engine area. Very strange.

Mxgrds said:
Well, I have exactly the same issue won't get it sorted out. What did you do to get rid of the air in the radiator?
Click to expand...
 
I finally broke down and took the X to a small local shop to redo the analysis I've done on the air problem.

He did compression and leak down tests, thermal imaging, and pressure tests. He doesn't think I've got an exhaust has leak or head gasket problem.

He DOES believe that my Allison header is surrounding my water pump pipe, is too close, and overheating it.

He thermal imaged the radiator, head, block, thermostat, etc and all seemed ok. But after warmup or a highway run the water pump pipe exceeds 280 degrees and he thinks is boiling the coolant in stop and go or idling situations. I think he's right...

My problems began when I installed the header and two of the runs are VERY close to the pipe. One of them runs parallel to it. I couldn't accurately image the pipe but the header itself which wraps around it was nearly 500 degrees.

Sent from my SAMSUNG-SM-G890A using Tapatalk
 
Interesting, and a definite possibility, your locally boiling the fluid and it's releasing air...

Sounds like it's time for a header wrap (or wrap the waterpipe) or a change to a factory cast 4/2 manifold and downpipe...

SteveC
 
IRC the Allison header was offered with a ceramic coating option, does yours have that?

My understanding of these Jet-Hot types of coatings is that they try to keep heat inside.

How about insulation or heat shielding, is there any room for that?
 
Yes I purchased the version with ceramic coating. My prior concern which I think is now verified by the mechanic is that two of the header tubes are VERY close to the water pipe. One is ~1/4", the other is perhaps 1/2" but also runs along the length of the water pipe. The link below shows some photos from the original install two years ago (uh, right before I realized I had an air problem) where you can get a feel for the issue: https://goo.gl/photos/6CRFD8aresStpRcg7

I had originally applied a small heat shield to the heater pipe. Last winter I removed it and replaced it with another to re-route my heater hoses which I believed were too close to the other two header tubes. When I reinstalled the new pipe I placed a thin layer of reflective heat tape on it.

But the mechanic more accurately thermal imaged what I could-not: The heater pipe measured over 280 degrees along several points. ...and there's not enough space between the pipe and exhaust tubes for adequate insulation. My options are a custom re-routed heat pipe (my mechanic can do that) which bends closer to the block and further from the header and then wrap the header with heat tape. ...or get a new header. Given what I paid for the header and exhaust I'm not very happy with either option.

I can understand why this problem may have been difficult to ascertain. The problem occurs after the engine is very warm and there is less airflow in the compartment at low/no speed. The symptom is elevated system temperature and air intrusion over time. But it doesn't take a rocket scientist to determine that running header tubes that nearly touch a cooling system pipe is a very bad idea. I noticed it immediately but assumed the design was fully vetted and it would be "good enough." It's not.

Would be curious to hear from other Allisons header owners. Keep in mind the design changed over time. I don't think the original design ran the passenger side tubes so close to the heat pipe. This change was made later when they re-routed the tubes so they'd no longer block injector shroud ducting (a problem with the first gen design). Pretty sure my header was one of the first of the modified versions.
 
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