am I right

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NickNorth

New Member
Posts
70
1997 4.0 V8 P38
I have reciently changed the radiator, and renewed the antifreeze bleeding the system as per RAVE however today I have noticed when the engine is running there is small bubbles rising from the bottom of the expansion bottle. I reckon there must be a leak on the head gaskets am I right, it has never risen over half way on the temp guage and runs fine no oil in water or water in oil and what looks like condensation only leaving the exhausts, the water isnt dropping at all and is clean with red antifreeze!
Any suggestions prior to replacing the head gaskets?

also does anyone struggle with the removal of the heat sheilds and bolts? do they need replacing as the one on the nearside seems slightly rusty near the bolts!
Nick.
 
make sure small radiator pipes are clear -air line

otherwise you can get localised boiling.

get garage to put their gas analyser probe over header tank when cap is off-if Hydrocarbons jump=hgf or liner slip
 
yup small radiator pipe is clear and gets hot so is flowing ok

when the heads are off how can liner slip be observed?

btw the bubbles start within 10 secs of starting and same if hot or cold!
 
NickNorth said:
yup small radiator pipe is clear and gets hot so is flowing ok

when the heads are off how can liner slip be observed?

btw the bubbles start within 10 secs of starting and same if hot or cold!
Click to expand...

If you are just getting small bubbles it is likely to be just minor airlocks being released. If the bubbles were combustion gas it would over pressure the system pretty quickly when hot and blow water out of cap. Try letting vehicle idle from cold with cap off and squeeze hoses to bleed system properly.
 
wammers said:
If you are just getting small bubbles it is likely to be just minor airlocks being released. If the bubbles were combustion gas it would over pressure the system pretty quickly when hot and blow water out of cap. Try letting vehicle idle from cold with cap off and squeeze hoses to bleed system properly.
Click to expand...


Depends on how bad the combustion gas to cooling leak is, first symptoms are rock hard hoses and steam cleaned spark plugs.
Slight miss on first start up.


As per my previous post-sniff test will prove it. (liquid of ebay=****e)

If liners have slipped you can feel with fingernail as liner should be level with top of block.
 
fanatic said:
Depends on how bad the combustion gas to cooling leak is, first symptoms are rock hard hoses and steam cleaned spark plugs.
Slight miss on first start up.


As per my previous post-sniff test will prove it. (liquid of ebay=****e)

If liners have slipped you can feel with fingernail as liner should be level with top of block.
Click to expand...

Yes and it needs watching. But seeing as he has just changed the radiator and there is no overheating or over pressure, it is just as likely trapped air. Steam cleaned plugs would result in water loss he does not complain of that.
 
An update folks,
I have noticed the little bubbles stop as soon as you lift the revs even a small amount over idle and the small pipe then flows coolant, I have noticed the water pump pully has some visable play in it and therefore think given that there is no overheaing, loss of power, cross contamination of fluids or leaking anywhere I wonder if the air is getting into the spindle on the pump and as the fan increases speed with revs the spindle centres itself and seats the seal on better section of the shaft. It does not increase the bubbles above idle it stopps and all looks normal so I am going to fit a new pump and see if this improves matters. Took it out today and booted it round and tbh it drives superb with no issues so air must be seeping in at the pump!
What do you think?
 
NickNorth said:
An update folks,
I have noticed the little bubbles stop as soon as you lift the revs even a small amount over idle and the small pipe then flows coolant, I have noticed the water pump pully has some visable play in it and therefore think given that there is no overheaing, loss of power, cross contamination of fluids or leaking anywhere I wonder if the air is getting into the spindle on the pump and as the fan increases speed with revs the spindle centres itself and seats the seal on better section of the shaft. It does not increase the bubbles above idle it stopps and all looks normal so I am going to fit a new pump and see if this improves matters. Took it out today and booted it round and tbh it drives superb with no issues so air must be seeping in at the pump!
What do you think?
Click to expand...

possible
 
That is not possible with the engine running, air cannot leak into a space where the pressure is greater than ambient. The mere presence of water with a head higher than the water pump says the pressure of that water at the pump will be greater than the air is outside it. Therefore air cannot enter, unless it is pumped in at a higher pressure than the water is exerting. The only possiblity is that as the water expands when hot then contracts when cold a partial vacuum is formed in the system and air could then be drawn into the system past a worn seal in the pump. I suggest you change your pump ASAP.
 
I see your pressure point however to see the bubbles i have the bottle open so the water is not at pressure as when it is when the lid is on!
 
wammers said:
That is not possible with the engine running, air cannot leak into a space where the pressure is greater than ambient. The mere presence of water with a head higher than the water pump says the pressure of that water at the pump will be greater than the air is outside it. Therefore air cannot enter, unless it is pumped in at a higher pressure than the water is exerting. The only possiblity is that as the water expands when hot then contracts when cold a partial vacuum is formed in the system and air could then be drawn into the system past a worn seal in the pump. I suggest you change your pump ASAP.
Click to expand...

Really bmw td lump I have seen two from cold suck air in from pump.

A good indication would be any staining in vicinity

We are going round in circles, as my previous post-get a sniff test
 
fanatic said:
Really bmw td lump I have seen two from cold suck air in from pump.

A good indication would be any staining in vicinity

We are going round in circles, as my previous post-get a sniff test
Click to expand...

No turning circles. If a partial vacuum exits in system due to cooling then air can be drawn in past a worn shaft seal. It is not possible to draw air in if pressure in system is greater than ambient. Just as damp air can be drawn into crankcase on cooling making the mayo many uniformed people think is a blown gasket. Simples.
 
fanatic said:
Still goes back to sniff test
HowStuffWorks "How Car Cooling Systems Work"
depression behind vanes as water exits
so it can draw air in and will leak stationary, unless the rad cap valve causes a slight vacum.
Click to expand...

Air with a negative pressure cannot flow into an area of positive pressure. What you are saying is that when you put a pin into a balloon outside air will rush into it. This is clearly not possible. Air at ambient 14.7 psi cannot flow into system because the weight of the water in the engine above the water pump gives a greater pressure than 14.7 psi. The only way air can enter at the water pump is if it has maybe a worn seal and a vacuum is developed as the system cools giving a negative pressure in the system of less than 14.7 psi. This can only happen with the engine cold, as when the engine warms it very quickly produces an even greater positive pressure at which air entering the system via water pump shaft seal would be impossible.
 
wammers said:
Air with a negative pressure cannot flow into an area of positive pressure. What you are saying is that when you put a pin into a balloon outside air will rush into it. This is clearly not possible. Air at ambient 14.7 psi cannot flow into system because the weight of the water in the engine above the water pump gives a greater pressure than 14.7 psi. The only way air can enter at the water pump is if it has maybe a worn seal and a vacuum is developed as the system cools giving a negative pressure in the system of less than 14.7 psi. This can only happen with the engine cold, as when the engine warms it very quickly produces an even greater positive pressure at which air entering the system via water pump shaft seal would be impossible.
Click to expand...

dun't forget cavitation!! and the oxygen content of water. and the venturi effect of a flowing liquid or air mass moving over a opening in the tube that it's moving thru.
 
The Mad Hat Man said:
i noo dat, Pikey ;).
Click to expand...


For those that don't


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