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Discussion Starter · #1 ·
Me and my tech are scratching the back of our heads......

500 miles on new head gasket...... now occasionally after driving and parking it wants to push out almost half the coolant from the overflow tube, but not all the time.

Here is where it becomes a little confusing;

Head is not cracked per my tech.
Head gasket is installed correctly and sealed per my tech.
Engine is not running hot.
Per the infa-red heat gun, no components under hood exceed 160-165 except exhaust manifolds.
Engine is not transferring any fluids...... none.
Radiator has been flushed with Liqui-Moly, cold water flushed, rechecked, clean no restrictions.
Thermostat opens at 190, engine temp drops to 175.... and levels at about 185.
Have bled the air from the coolant system per the manual.
Engine will idle all day long and not exceed 185.
New rad cap from Classic Alfa checks out fine.
Just replaced the original water pump with new from Classic, thinking we might have cavitation.
Engine is not smoking, or pushing anything excessive out the tail pipe..... other than a little condensation which goes away.

What the heck are we missing....... ?

Thanks in advance.
 

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Thermostat should be a 175 or 180.

Has the radiator been rodded out by a radiator shop. Thats the only way to really clean one and be sure.
 

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Discussion Starter · #3 ·
Jim,

Thank you for your reply.... no I dont think so, but I'll double check.

I think since the Liqui-Moly was used, drained, then the cold water hose to rinse,with the water coming out the bottom outlet as fast as it was going in the top and clean, they might have assumed that it was good to go.....?
 

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I've had ones where the radiator shop told me they were flowing fine. But they would run slightly hot or do odd things at times. I would take them back and stand there while they took the cap off. Every time some of them would either be plugged up or partially stopped up.

It doesn't take many to start giving you problems.
 

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So am I understanding this right: it's parked and turned off and dumping coolant? That's a rather odd problem to have. Probably not the head gasket, given that there's no cylinder pressure when off. And if it's running at proper temp while driving the radiator isn't the first thing I'd suspect: the radiator is only doing anything significant when air is flowing through it.

The coolant temperature will typically rise for a bit in parts of the engine when you turn off the car, but it shouldn't generate enough pressure to push the coolant out. I know you said you tested the radiator cap, but even if it tested good I'd suggest trying a new one. Also carefully inspect the radiator neck for any cracks or places where the cap might not be sealing properly.

I don't recall if the Duetto has an overflow tank, but if it does note that you need a cap with both top and bottom seals for the neck or things won't work properly.
 

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Discussion Starter · #6 ·
Thanks Jim....... Rick and I will see about this. I'm not sure if any rad shop in our town does 'rodding', but we will find out.

I guess I should also mention that my heater core is bypassed and has been for many years...... and the liner protrusion was checked before head gasket installation.
 

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Discussion Starter · #7 ·
The overflow tank and recovery system didn't come out until the 1750 I believe. Another rad cap has been tried... in fact 3.....
 

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It seems that the cooling system is heat soaking and overcoming the radiator cap pressure rating. Square cap is 10 psi and round cap is 7 psi. If you have on the round cap, try a square one. Just a thought.
 

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Me and my tech are scratching the back of our heads......

500 miles on new head gasket...... now occasionally after driving and parking it wants to push out almost half the coolant from the overflow tube, but not all the time.

Here is where it becomes a little confusing;

Head is not cracked per my tech.
Head gasket is installed correctly and sealed per my tech.
Engine is not running hot.
Per the infa-red heat gun, no components under hood exceed 160-165 except exhaust manifolds.
Engine is not transferring any fluids...... none.
Radiator has been flushed with Liqui-Moly, cold water flushed, rechecked, clean no restrictions.
Thermostat opens at 190, engine temp drops to 175.... and levels at about 185.
Have bled the air from the coolant system per the manual.
Engine will idle all day long and not exceed 185.
New rad cap from Classic Alfa checks out fine.
Just replaced the original water pump with new from Classic, thinking we might have cavitation.
Engine is not smoking, or pushing anything excessive out the tail pipe..... other than a little condensation which goes away.

What the heck are we missing....... ?

Thanks in advance.
Me and my tech are scratching the back of our heads......

500 miles on new head gasket...... now occasionally after driving and parking it wants to push out almost half the coolant from the overflow tube, but not all the time.

Here is where it becomes a little confusing;

Head is not cracked per my tech.
Head gasket is installed correctly and sealed per my tech.
Engine is not running hot.
Per the infa-red heat gun, no components under hood exceed 160-165 except exhaust manifolds.
Engine is not transferring any fluids...... none.
Radiator has been flushed with Liqui-Moly, cold water flushed, rechecked, clean no restrictions.
Thermostat opens at 190, engine temp drops to 175.... and levels at about 185.
Have bled the air from the coolant system per the manual.
Engine will idle all day long and not exceed 185.
New rad cap from Classic Alfa checks out fine.
Just replaced the original water pump with new from Classic, thinking we might have cavitation.
Engine is not smoking, or pushing anything excessive out the tail pipe..... other than a little condensation which goes away.

What the heck are we missing....... ?

Thanks in advance.
I don’t know if this has anything to do with it but when I was rebuilding the head on my 1600 GT Jr I ordered a Reinz head gasket for a 1600 engine. Turns out that the head on my 1600 had extra coolant pathway holes in the head and the gasket they sent me did not have these extra holes yet it was also for a 1600 engine. I almost installed it this way until I looked at the old gasket. I then had to to take the gasket to a shop to have these extra coolant passage holes punched into the gasket. It’s worth to have a look at your old gasket. Again I’m sure there are people on this post that know if this is a possibility. I only know this happened to me. Good luck.
 

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It seems that the cooling system is heat soaking and overcoming the radiator cap pressure rating. Square cap is 10 psi and round cap is 7 psi. If you have on the round cap, try a square one.
Gee, I don't know about trying that "fix". It sounds like the situation where someone's 7 amp fuse keeps blowing, so they "fix" it by installing a 10 amp fuse. Yes, it might stop one problem, but it might also create another. I've always heard that Alfa engines shouldn't be run at high coolant pressures due to their dicey head gasket sealing.
 

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I don’t know if this has anything to do with it but when I was rebuilding the head on my 1600 GT Jr I ordered a Reinz head gasket for a 1600 engine. Turns out that the head on my 1600 had extra coolant pathway holes in the head and the gasket they sent me did not have these extra holes yet it was also for a 1600 engine. I almost installed it this way until I looked at the old gasket. I then had to to take the gasket to a shop to have these extra coolant passage holes punched into the gasket. It’s worth to have a look at your old gasket. Again I’m sure there are people on this post that know if this is a possibility. I only know this happened to me. Good luck.
I asked @Gordon Raymond about that. As the 1600 i'm building has the holes in the head. But the gasket on the engine did not.

He said not to use the gasket with the holes in it. That it caused some problem and Alfa went to head gaskets with out holes for all the 1600 engines. Send him a PM and ask.
 

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Discussion Starter · #13 ·
Classic Alfa also confirmed the standard production 1600 does not require the head gasket with the extra holes..... even if used by mistake, it would not cause a problem , or this specific problem, we are experiencing presently.
 

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Then I don’t understand why Alfa would set up production to have them bored only to say they are not necessary. They must be there for a reason.
 

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Pretty simple. The extra holes caused too much coolant flow in the head passages, and heat transfer was variable with fluctuating head chamber temperatures resulting in poor chamber burn characteristics. This became an issue with the early 1600, sand cast GTA heads with the holes. It was discovered that by threading the holes and screwing in threaded aluminum rod, more consistent burn (greater Hp) was possible. This fix is discussed in the CAS handbook, 2nd edition. First on the GTA heads, then used on the single plug heads. When the 1750 engine was developed, the heads lacked those holes AND the 1750 head gaskets also had no holes. We then found using 1750 head gaskets on 1600 single plug engines and GTA's the threaded rod fix was unnecessary. Issues solved.
 
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Then I don’t understand why Alfa would set up production to have them bored only to say they are not necessary. They must be there for a reason.
At some point Alfa stoped boring the holes. As I've seen some 1600 heads without the holes.
 

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I had a similar issue with my 2009 Mini S. (I know it's not an Alfa)
I took it in for a radiator flush because I noticed that the electric fan was staying on longer
after the engine was shut down. No indication of over heating, etc. ran fine.
I had just finished a 1000 mile run.
When the over flow cap was loosened (right after shut down. at the shop) a lot of steam and water came out. Never ran across this before. He did a head gasket replace and all is well again. Best we could think of was a clog in the head water passages somewhere were blocked
causing a pocket of steam to get stuck caught some where and after the pressure was released and the steam and water went out the cap.
The head was sent out to a shop for cleaning and skim.
No other work was done on the car.
 

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I had a similar issue with my 2009 Mini S. (I know it's not an Alfa)
I took it in for a radiator flush because I noticed that the electric fan was staying on longer
after the engine was shut down. No indication of over heating, etc. ran fine.
I had just finished a 1000 mile run.
When the over flow cap was loosened (right after shut down. at the shop) a lot of steam and water came out. Never ran across this before. He did a head gasket replace and all is well again. Best we could think of was a clog in the head water passages somewhere were blocked
causing a pocket of steam to get stuck caught some where and after the pressure was released and the steam and water went out the cap.
The head was sent out to a shop for cleaning and skim.
No other work was done on the car.
2nd gen mini's are known for needing head gaskets at around 70,000 plus miles.
 

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What is the psi rating on the cap? The usual catalogs show either .5 bar = 7.25 psi or .7 bar = 10.psi. I advise testing your cap again with a hand held pressure tester. Honestly, I have used 12-14psi caps for decades with no ill effects. Also, look carefully at the seal on the cap and the mating surface on the radiator. Also, I would run the engine from cold (perhaps with out the fan and shroud) and just when the thermostat opens, lay your palm across the fins of the radiator and feel for how the heat transfers. A rad with clogged tubes will have cold(er) spots that you will easily feel. Jim is correct. The only way to properly refurbish (clean) one of these (old) radiators is to remove the top tank and, using a thin rod, clean each tube. This is the normal, and proper practice that all old-time radiator guys use. I'd try the 12psi cap first.
 

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I asked my 84 year old father what he thought. He is a retired A-grade mechanic. His first comment was radiator cap followed by how good is the radiator ... which echoes some of the posts above.

If the mating surface of the radiator cap seal is compromised it might be letting water by at a lower pressure than it should as AndyLarry said
Pete
 
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