Ford Lehman 120 Cooling System Air Bleed

[VicTrawler]

I just replaced the cooling hoses (freshwater side) on my Lehman and I want to ensure I'm completely purging all air from the system.

I followed the instructions in the manual, which are:

- Fill the system and purge the exhaust manifold while doing so.
- Top up the expansion tank.
- Run the engine at 900 RPM and wait for the thermostat to open, then keep the expansion tank topped up.

Now, when does the thermostat open? I kept the radiator cap (expansion tank cap) off the entire time, all the way up to just about 180F. I did notice more turbulence when it got closer to 180F, so I'm assuming that was the thermostat opening. That being said, I had bubbles almost the entire time, but they did seem to subside to almost nothing UNLESS I throttled up to 1500+ RPM, in neutral, then I got more air.

What was also weird is that after I throttled back down to 700-800 RPM, I'd get an arcing spray of coolant out of the radiator cap. What the heck is that? Is that a tonne of air trying to escape? It also seemed to be random if/when it would do it. I would throttle back up to 1500 RPM and back down to 700 or so and it would only have an arcing spray about half the time.

And yes I will bleed the system from the exhaust manifold bleed valve once everything cools down.

I also didn't have anything in the overflow (plastic) tank during this process as I had not yet re-filled it.

Did I do any of this wrong?

One more thing, I was getting steam (I hope) from the radiator cap opening. It didn't smell like exhaust. I'm assuming that's normal. I think if it was exhaust, the bubbling would've been far more significant... unless that's what the arcing spray was... hope not, because that would be a head gasket.

Pardon the rambling. Any suggestions/input would be much appreciated! All of this effort is to try to tackle an overheating situation.

 

[jleonard]

I can't get my thermostat to open in neutral at the dock.
You should have coolant in the overflow tank.
Sounds like you did it correctly, but I never got any spray out of the cap.
Maybe a little bubble of air that overflowed..... but I always leave air room below the cap level.

 

[VicTrawler]

Thanks Jay. Maybe my thermostat was occasionally opening (hence the spray), whereas yours didn't, and that's why you never saw the spray.

Thinking about it now, when I brought the engine up to 1500 RPM, that would obviously increase the engine operating temp. From there, suddenly bringing it down to 700 and reducing the pump speed and flow rate, perhaps that would cause just enough of an increase in coolant temp to pop the thermostat. It was probably right on the edge.

 

[Xsbank]

I believe the rad cap should be closed and the overflow bottle topped up. If you have any air left it will purge out the overflow and be replaced with coolant when it cools.

 

[RT Firefly]

Greetings,
Mr. VT. Your empty overflow tank doesn't enter into the picture at all at this point.

Mr. X, just saw your post. IF the cap is on and there is still air in the system, won't this cause a danger with unequal cooling if there happens to be an area devoid of coolant?

 

[Martin J]

Open the cock

If you look at the forward end of the manifold you will see a petcock. Open that as its running and continue til you get the coolant flowing out. The engine is airlocked and your superheating the water and air in parts etc.

 

[SeaMoose]

Not at the boat so can't give exact location, but I recall that on mine there is a little valve near the top of the engine that I opened while filling with coolant that helped excess air escape.

That being said other posters are correct, put the cap on and fill the coolant overflow tank the bubbles will work out. You should not see anything squirting out the cap, I'd check that it was properly on there.

HTH

 

[BruceK]

If you look at the forward end of the manifold you will see a petcock. Open that as its running and continue til you get the coolant flowing out. The engine is airlocked and your superheating the water and air in parts etc.

According to my Lehman Manual, opening the petcock with the engine running is a big No No.
Manual(p19) says,all in caps so I quote it that way,:" DO NOT OPEN AIR BLEED VALVE WHILE ENGINE IS RUNNING AS THIS WILL DRAW AIR INTO THE SYSTEM AND DISPLACE WATER AND CAUSE OVERHEATING".
The warning appears twice. The one I didn`t quote is underlined as well as in caps.
You open it while refilling, or while topping up. Not otherwise as I understand it.
To the OP, I suggest let it sit and cool, then open the valve and add more coolant and see what happens.
I know after a complete draining of my port engine as part of a thorough flush(? build up at no.6) it took some work to get the air out, but I wasn`t present when it was done.

 

[RT Firefly]

Greetings,
Mr. BK. Ya beat me to it. DO NOT OPEN THE VALVE ON THE EXHAUST MANIFOLD WHILE THE ENGINE IS RUNNING!!!! I may add, I agree with allowing the engine to cool before opening above mentioned valve.

In addition to potentially drawing in air, the opposite may happen and you'll be sprayed with boiling hot coolant....I can attest from a LOT of experience, burns are one of the worst injuries.

 

[psneeld]

First off, you have to know whether the expansion tank has been modified to act like a regular radiator with a dual action radiator cap and overflow bottle.

If you have the old style radiator cap, it will not suck in fluid from any over flow bottle someone might have rigged.

The adapted expansion tank with new style radiator cap will, and has the proper setup for an overflow bottle.

I have had a head gasket leak for a couple years now, combustion to coolant. It fills fhe manifold upper end full of air, creates bubbles in the expansion tank and pushes most of the fluid out of the tank.

Last year I did the conversion to help with troubleshooting. Because of the combustion leak and air in the manifold, it rarely sucked enough fluid back to fill that air pocket.

Replacing the head gasket this week.

And yes, according to all accounts, do not open the percock on top of the manifold when the engine is running.

 

[Xsbank]

Hi RT, most of the other posters have got it, if the engine is healthy, filling and bleeding with the petcock is the correct procedure, then run it with the cap closed. There should not be any air in there anymore if properly bled with the petcock. I would check it again once it is cooled.

As far as the filler cap is concerned, I did assume that the American Diesel overflow mod had been done, I made a huge assumption that there might be anyone still running a Lehman with coolant being caught in a bucket!

 

[VicTrawler]

I will definitely not be opening the exhaust manifold bleed while the engine is running, or while stopped and hot, as per the warning in the manual.

Will the air actually purge itself out the overflow? I don't see why it wouldn't, but that's not in accordance with the air purge procedure as per the manual. That being said, the manual was written before the mod came out to modify the header tank and rad cap for the overflow tank.

I do have the adapted expansion tank and new style radiator cap with duel seals.

I should have been clear when I said that fluid was squirting out of the cap - the cap was not on at that point. It was squirting out of the uncapped opening as I still had the cap off to conduct the air purge procedure as per the manual.

So I just took the boat out for a spin. Still hitting 200F at 1800 RPM. Once it cools back down, I will confirm if I've lost any coolant. I had a couple of leaks which I think I've now solved, but if I'm still losing coolant, I'll have to dig deeper (probably the exhaust manifold next). The troubleshooting continues...

 

[Tator]

Had a similar problem a long time ago and, if I remember correctly, the coolant was going into the injection elbow from the exhaust manifold due to a leaky gasket at the joint between the manifold and elbow.

Tator

 

[VicTrawler]

Had a similar problem a long time ago and, if I remember correctly, the coolant was going into the injection elbow from the exhaust manifold due to a leaky gasket at the joint between the manifold and elbow.

Tator

Thanks Tator - that supports my suspicions. I will have the elbow off today for a look. Will post an update with my findings.

 

[VicTrawler]

Well, I replaced the gasket at the exhaust manifold / elbow. There was no obvious damage to the gasket. Regardless, hopefully that improves the situation. Luckily did not break off any bolt heads.

 

[VicTrawler]

Here's a video of the spray that I occasionally see from the radiator with the cap off. I just started the engine cold and it did this. It seems random as to whether it will do this or not. If it was a head gasket, wouldn't it be continuous and not stop?

Any ideas as to what the cause of this could be, please let me know.

Edit: my theory is that this is air being purged from the cooling system (I had just re-filled it). The diameter of the spray seems to be similar to the size of the thermostat bleed hole.

 

[RT Firefly]

Greetings,
Mr. VT. Quite a dramatic "spurt" but aside from the fact this MAY be a symptom of the problems you're having, could it also be normal operation and not related to your problem at all? Have you ever had the cap off while running before? I know I never have so I would have no way of knowing whether this "spurt" was a normal or abnormal occurrence. NOT trying to be difficult at all, just throwing ideas out...

 

[VicTrawler]

Greetings,
Mr. VT. Quite a dramatic "spurt" but aside from the fact this MAY be a symptom of the problems you're having, could it also be normal operation and not related to your problem at all? Have you ever had the cap off while running before? I know I never have so I would have no way of knowing whether this "spurt" was a normal or abnormal occurrence. NOT trying to be difficult at all, just throwing ideas out...

RTF, I had never run the engine with the radiator cap off until I replaced the FW pump last year and carried out the air purge procedure. That being said, I don't remember if I saw that spray or not, at that time.

Just to add to this, I just ran the engine again. It immediately started spraying, but I had a glass jar handy which I placed over top of the opening so I could both contain the spray and watch if it stopped. It did indeed stop after about two or three minutes.

 

[RT Firefly]

Greetings,
Mr. VC. Good idea with the glass jar. Now, here's a thought...I'm pretty sure some thermostats have a hole in the body to allow some coolant through before the thermostat opens. Could it be that the "spurt" is simply coolant shooting out under pressure and the reason it stops after 3 minutes is the valve is starting to open thus relieving said pressure and allowing greater flow past the valve itself ?????

 

[VicTrawler]

Greetings,
Mr. VC. Good idea with the glass jar. Now, here's a thought...I'm pretty sure some thermostats have a hole in the body to allow some coolant through before the thermostat opens. Could it be that the "spurt" is simply coolant shooting out under pressure and the reason it stops after 3 minutes is the valve is starting to open thus relieving said pressure and allowing greater flow past the valve itself ?????

I added an "Edit" to my post, suggesting the same theory. I think that's what it is - I'm glad you agree.

I very likely have air in my system because I just changed out the coolant yesterday and have only run the engine a couple of times, since. It probably stops spurting because that particular pocket of air has been purged. The thermostat wouldn't be opening with the engine that cold (unless it's defective).

 

[psneeld]

The best way to check for a head gasket compression to coolant leak is with a coolant system pressure tester. At least in my experience.

I had a very sr and experienced lehman mech aboard checking a mystery noise and had mentioned my possible head gasket issue.

He put on a oressure tester and let it build but bleed it off as the engine warmed up. After 20 minutesvor so of running, he showed me how pressure kept building and blowing bubbles through the tubing to the overflow thank.

It confirmed my suspicions, despite the chemical test kit I bought that said all was fine.

 

[VicTrawler]

The best way to check for a head gasket compression to coolant leak is with a coolant system pressure tester. At least in my experience.

I had a very sr and experienced lehman mech aboard checking a mystery noise and had mentioned my possible head gasket issue.

He put on a oressure tester and let it build but bleed it off as the engine warmed up. After 20 minutesvor so of running, he showed me how pressure kept building and blowing bubbles through the tubing to the overflow thank.

It confirmed my suspicions, despite the chemical test kit I bought that said all was fine.

That is a very good idea. I already have the pressure test kit.

I will try bleeding air a few more times, and then try the pressure test with the engine running.

 

[Nomad Willy]

The best reason to not run an engine w the cap off is that no pressure above atmospheric will be in the cooling system. Therfore water will boil at 212 f. and if it does coolant will come gushing up out of the filler hole like at yellowstone park. Perhaps that's similar to the OP's "spray" event.

Anyway that's why they say not to run the engine w the cap off. With the cap on the coolant temp can get to perhaps 225f w/o boiling halving about 13psi pressure in the system. But re the above posts boiling may not occur as diesels make so little heat at idle.

My method on filling is to do it very very slowly w the engine not running. Fill it while you're doing something else and every now and then add a small amount of coolant like perhaps 1/2 a cupful .. or a cup. Pour the coolant from the cup very slowly. If possible fill the exhaust manifold first. In my engine rhe expansion tank is part of the exhaust manifold. There are some obvious times when you can add coolant more quickly. Then when it's about 1" from full in the expansion tank put the cap on an start the engine.

On most engines there is a cap on top of the thermostat. Most now are aluminum. Spot your lazer heat sensor on the cap and do it often. When it goes from cold to warm temps suddenly the thermostat just opened. If no lazor temp sensor tap the cap w finger or a thin glove. Then after a time at various engine speeds (higher speeds only for very short periods) all the air should burp out or up and reside in the engine expansion chamber. No need to use a remote expansion tank. The air space in the tank is plenty. You can (however) use a remote tank higher (a foot or two is best) than the engine tank. Some say this will keep air and thus oxygen out of the system. It's fly stuff IMO.

 

[psneeld]

I can see not trying to vary RPMs from idle to full throttle with the cap off, but idle to fast idle with the cap off is done all the time for different tests.

No big deal....I have never seen a warning to not run with tbe cap off, just not to remove it while the engine is hot.

 

[senangsekali]

The same thing would happen in any engine with cap off and reving engine. This is normal. Fill with the bleed caps off until coolant run out of bleed screw then replace bleed screws. Put cap on. Start the engine. Let it run up to normal temp. Let cool then check. Fill and continue. Eventually you will get all the air out. Also get a lazer temperature tool. Shoot the temp at the coolers. Should stay around 185 ish.

 

[Capt.Bill11]

Remember the level of the fluid in the tank should be about an inch below the lip of the tank cap neck.

 

[VicTrawler]

The best way to check for a head gasket compression to coolant leak is with a coolant system pressure tester. At least in my experience.

I had a very sr and experienced lehman mech aboard checking a mystery noise and had mentioned my possible head gasket issue.

He put on a oressure tester and let it build but bleed it off as the engine warmed up. After 20 minutesvor so of running, he showed me how pressure kept building and blowing bubbles through the tubing to the overflow thank.

It confirmed my suspicions, despite the chemical test kit I bought that said all was fine.

Just to clarify...

Obviously pressure will build in a perfectly healthy engine as the coolant temp increases. Is the purpose of this test to check that pressure is not still building after the coolant reaches a steady temp at idle?

 

[Capt.Bill11]

Just to clarify...

Obviously pressure will build in a perfectly healthy engine as the coolant temp increases. Is the purpose of this test to check that pressure is not still building after the coolant reaches a steady temp at idle?

Yes

 

[psneeld]

Thanks Capt.!!!

 

[VicTrawler]

Yes

Thanks!