Vaccuum in cooling system

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Veikra

Member
Dec 19, 2011
260
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Montreal, Canada
I'm not sure where to post technical questions, so Im trying here. Sorry if it's not the right spot.

Here goes. I'm trouble shooting puking coolant. I thought headgasket but when the truck cools down the radiator hose doesnt stay hard.

Even weirder, most of the time, there will be vacuum in the cooling system on the next day.

ive noticed the few times it puked coolant, I had many many stops and starts. Such has visiting many places for grocery.

Truck does not have bubbles coming out the overflow bottle, and never smoke. 212 000 miles 575hours

Im thinking trapped air? I have bypassed the heater core, it didnt change anything, but there was air in the top hose when I disconnected it.


My question is: If I have vaccuum in my system more often than not after cool down , does it rule out a headgasket issue? Wouldnt the cylinder's air cancel the vacuum if gaskets where bad?

Thanks for your oily wisdom
 
blk smoke lb7

blk smoke lb7

<-----Lots of green $
Nov 8, 2010
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belvidere,ill
Sounds like your coolant cap has the vent holes possible plugged id try a new cap.

If you think there is air in there you can bleed the air out thru the bleed screw in the top of the t stat housing.It is possible your w/p impeller could have been loosend and isn't pushing coolant as it should.
 
V

Veikra

Member
Dec 19, 2011
260
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Montreal, Canada
I'm off to the dealership then. Shouldn't be too expensive.

when I open it when cooled down, sometimes the coolant in the overflow bottle goes down with a gurgle sound. It would explain that

If my water pump had the impeler loose and not pushing enough, Shouldn't I overheat?
 
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Veikra

Member
Dec 19, 2011
260
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16
Montreal, Canada
I took the cap off, cleaned it and noticed that the bottom of the cap wasnt centered. I found that odd and then looked for a cause. here's what I saw

Normal side openings are like this one:
photo-vi.jpg

Now for the one on the opposite side:
photo-vi.jpg


the other 2 openings are half obstructed by this kind of seal. Looks like the seal expanded outward, caused the 'piston' to be sideway.

Hopefully this is what's causing the whole issue . EIther way, this cap is not good and needs replacing.

Thanks a lot guys. I will replace the cap and check for symptoms in the following week. :)
 
Last edited:
02greysixer

02greysixer

Active member
Jun 4, 2011
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North Central FL
I'm going to have th check this out. Mines been doing the same thing, I've just been to in denial to question why. I had already assumed the worst and it was just the beginning stage of a blown head gasket

sent from a galaxy far far away
 
V

Veikra

Member
Dec 19, 2011
260
0
16
Montreal, Canada
c30: mine looked more like a displaced seal. It wasnt so dirty. I got the new one and sure enough, the seal doesnt seat like this on the new one. Im waiting for the truck to cool down to replace it.

Im still assuming the worst, but first things first, especially when you stumble on damaged parts that can cause a false positive

Cap cost me 22$ at the dealership
 
V

Veikra

Member
Dec 19, 2011
260
0
16
Montreal, Canada
Cap solved the vaccuum in my cooling system. I have a headgasket issue now. The issue only appear on high boost, hence why it was so weird.

It spews 1.2 liter if I fill it correctly. then it stays stable for a long time or until I really floor it then it might lose a few cc per week.

I roll dices on the #7 toward firewall.

Ps: my egr cooler has not been removed yet
 
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Veikra

Member
Dec 19, 2011
260
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16
Montreal, Canada
I found my small leak. It drips a little between engine and transmission. I need to powerwash the engine to find the exact place. Truck is still spewing out the first 1.2 liter, but I catch it in a bottle
 
lifteddirty

lifteddirty

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Aug 20, 2013
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casper wy
If it was your EGR cooler your coolant will usually have a pretty nasty smell or it could possibly even turn blackish brown color. Not saying that it rules it out completely. If i were you i would do the egr delete, head gaskets and studs all at the same time. It definitely won't hurt anything.:thumb:
 
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jlawles2

Well-known member
Jan 28, 2010
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Danbury, TX
You state that there are bubbles in the overflow tank.

If this is when the truck is cold.... This immediately leads me to say head gaskets. Under idle conditions none of the systems in the truck can produce enough pressure to push air into the overflow.
 
V

Veikra

Member
Dec 19, 2011
260
0
16
Montreal, Canada
Lifteddirty: I do have some black deposit in my overflow tank.


jlawles2
"You state that there are bubbles in the overflow tank. "

No I have no bubbles at all, cold or warm. I get air trapped inside my cooling system somehow. I need to run the truck until warm and pressurized for it to spew.

After inspection, finally got to the waterpump weap hole, and found signs of long term leakage. It could explain where the air is coming from but not were the black stuff in the overflow comes.

Im prepared to do gaskets, and change waterpump, put egr delete and arp headstuds. But on the other hand i wouldnt know what it was.

Could I make myself some block off plates to test the egr? Im mostly intrigued in the connection between the egr and intake tube ( the one with the egr path in it, on top of the engine)

Oh, I just ruled out the white smoke on wide open throttle. It's not burning prestone, it's fuel starvation. Only happens below 1/4 tank. Anything over I can floor it and there is no white smoke at all.

This along with the waterpump leaking, I have found where most of the lost prestone is going.



Recap: Brown stuff in overflow could be gaskets, egr or maybe stop leak stuff the previous owner may have put in. The more I add prestone the more it seems to clear up in color.

If im losing my coolant through the waterpump and not the gaskets, then the egr could be good.

Hypothesis 1: the headgasket would account for the brown residues and the air getting in the cooling. It could also push the coolant out the broken waterpump.

Hypothesis 2: The waterpump lets air in, which accumulate and gets compressed at the top of the engine Air gets in between coolant , so water has to come out to a certain level before the air gets out. Here is where the 1.2 liter mesurement comes in. That's why I mesure it.

I could always use the shotgun approch, but since he's not behaving like a typical headgasket issue I think there may be something to learn here.

And yes, Im a scientist:thumb:

I was about to put a coolant pressure gauge to confirm the bad gaskets, but with the waterpump im afraid it would not show the rise in pressure and bleed pressure through the waterpump instead. False negative would not help me.

Truck still acts perfectly normal, pulls STRONG, no overheat.

I hope I am clear in the infos I provide. Else just ask me to clarify

PS: It's a sweet engine, gosh I wish I had a ZF6 laying around
 
V

Veikra

Member
Dec 19, 2011
260
0
16
Montreal, Canada
OK, I installed a gauge and can not get the pressure to go over 15/16psi. I would have expected a spike in pressure as the cap cannot bleed a large amount. I got a rise in temperature once.

What it means is I can replace the waterpump without risking to blow the seals of the new one.

Now, only thing left to do before gasket is the EGR delete next week. It's probably the gaskets, but the truck has 350 000km and egr is still on.
 
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