Changing antifreeze - engine overheating

[blackrose]

I've just drained the whole cooling system down, flushed it through, run it with water inside and drained it again. It ran fine with water but now that I've put the new antifreeze in it's overheating?

 

I can't figure it out. I bled both skin tanks but the pipes to/from the calorifier are cold. The coolant reservoir was half full so perhaps there was a big airlock somewhere and there wasn't enough antifreeze in even though I put 40 litres in.

 

I can't look in the reservoir now as it's too hot. Shall I just wait until it's cooled down and look inside and top it up? I can't imagine the skin tanks will need bleeding again? I'm jumping ahead, but if the coolant in the reservoir did suddenly disappear into the system would I have damaged the coolant pump by running it dry? I think it ran for about 15 mins in total before I realised it was overheating. I thought it was just a hot spot and the coolant needed pumping around so I revved the engine harder but it just got hotter. It reached 100C before I switched it off.

Edited June 19, 2019 by blackrose

[Sea Dog]

2 minutes ago, blackrose said:

I can't figure it out. 

Assuming you've ruled out an airlock, did you pre mix yhe coolant? If you put water and antifreeze in the system separately they can stratify.  

[WotEver]

14 minutes ago, blackrose said:

the pipes to/from the calorifier are cold

Then you have an airlock. 

[blackrose]

13 minutes ago, Sea Dog said:

Assuming you've ruled out an airlock, did you pre mix yhe coolant? If you put water and antifreeze in the system separately they can stratify.  

It was bought premixed. I haven't ruled out an airlock - far from it.

3 minutes ago, WotEver said:

Then you have an airlock. 

Yes, I guess so.

Edited June 19, 2019 by blackrose

[Guest]

 

Quote

Did you run it for a while with the pressure cap removed, this can sometimes do the business, as well as squeezing the main flexibles to "pump" the stuff around. My engine has a habit of airlocking in the calorifier loops so I fitted a bleed tap at the highest point. Works a treat. If these calorifier feeds are flexibles, you could try disconnecting at highest point and filling with a funnel. We used to do this when banger racing as we put the rad where the back window once lived ie higher than the engine

 

Edited June 19, 2019 by Guest

[blackrose]

It cooled down a bit so I just checked the coolant reservoir and it's still half full. The skin tanks are both full too.

 

I've started the engine again to see what happens

19 minutes ago, catweasel said:

 

 

Ok not sure what's happened to your post but thanks for the advice. If it still overheats I'll try that tomorrow, although I'm out of antifreeze now.

 

Edit. It's already back up to 90C so I'm switching off. It usually idles at no more than 80C. It's never done this before when I've changed the antifreeze so I'm a bit perplexed.

 

As the coolant level in the reservoir is higher than the water pump presumably I haven't run it dry?

Edited June 19, 2019 by blackrose

[bizzard]

1 hour ago, blackrose said:

It cooled down a bit so I just checked the coolant reservoir and it's still half full. The skin tanks are both full too.

 

I've started the engine again to see what happens

Ok not sure what's happened to your post but thanks for the advice. If it still overheats I'll try that tomorrow, although I'm out of antifreeze now.

 

Edit. It's already back up to 90C so I'm switching off. It usually idles at no more than 80C. It's never done this before when I've changed the antifreeze so I'm a bit perplexed.

 

As the coolant level in the reservoir is higher than the water pump presumably I haven't run it dry?

Top it up and leave the header tank cap off overnight, often any air will gradually rise and disperse.

[Cheshire cat]

Definitely an airlock. Are the hoses to the skin tanks also cold?

 

If you follow Bizzard's advice and the water level doesn't drop over night I'd pull a hose off the waterpump or thermostat housing and see whether you get water or air.

If it's air wait for the water to come through and put the hose back on. Top up and try running the engine again. 

[bizzard]

I doubt if you've damaged the engines water pump. They are only circulation assisters. The impellors are either cast iron or pressed steel and will stand any high heat even running dry. Only once have I had one fail and that was on a Vauxhall Cavallier 1600. The lad that owned it had driven it for about 40 miles with hardly any water in it after a leak in the rad which he wasn't aware off. It had overheated big time, how the engine had't seized or blown up I'll never know. I fixed the leak, filled it up and started it up. It got hotter and hotter, mmm! I start checking for blockages, head gasket, thermostat and coolant flow.  No flow even with no thermostat. Removed water pump in the end and lo! cast iron impellor broken into bits. New pump and all good. How that engine survived that severe overheat I'll never know, it must have been almost glowing red hot.

[blackrose]

Thanks. The hoses to the skin tanks were cold too so perhaps I have multiple airlocks. I'm going to try bleeding the calorifier circuit first. I think I know what's happened; I was probably a bit too thorough in sucking all the old antifreeze out with my wetvac so the whole system was full of air. But if it's just one airlock in the calorifier, would an airlock in the calorifier circuit prevent the rest of the cooling system circulating?

Edited June 20, 2019 by blackrose

[Nightwatch]

Your engine needs a good burp! Do as suggested. Either run it with the cap off, the header tanks, you can leave yours on, or leave overnight.

[Chewbacka]

Try giving the fat hoses to and from the skin tanks a good fast squeeze to shift the air along, might help.

 

Another thought - sounds like you did a fair bit of flushing when changing the coolant, possibly you have stirred up all the crud and it has blocked the thermostat which would prevent flow to the skin tanks. 

Edited June 20, 2019 by Chewbacka

[blackrose]

Yes, I'll try all of the above and hope it's not a blocked thermostat. Just waiting for some more of the same antifreeze to arrive.

[cuthound]

Is your calorifier a horizontal one? They can be bu**ers to bleed, especially if the top coil is slightly higher than the engine.

 

I had to resort to modifying the pipework on one boat so thst there was a bleed valve well above the horizontal calorifier.

[Chewbacka]

30 minutes ago, cuthound said:

Is your calorifier a horizontal one? They can be bu**ers to bleed, especially if the top coil is slightly higher than the engine.

 

I had to resort to modifying the pipework on one boat so thst there was a bleed valve well above the horizontal calorifier.

Agreed, but the an air lock in the calorifier would not lead to engine overheat (op reports skin tanks remain cold).

[blackrose]

1 hour ago, cuthound said:

Is your calorifier a horizontal one? They can be bu**ers to bleed, especially if the top coil is slightly higher than the engine.

 

I had to resort to modifying the pipework on one boat so thst there was a bleed valve well above the horizontal calorifier.

No it's vertical

[blackrose]

Ok, I've taken out the thermostat and had a look. It seemed ok. I gave it a rinse and a bit of a clean and put it back in. Ran the engine and took one of the feeds to the calorifier off but it looked like it was full of the water that I'd flushed it through with, no sign of red antifreeze so it's not getting through. Running with the cap off didn't bleed the system as it's still overheating.

 

I've got a feeling that there's no coolant getting to the thermostat as the level in the reservoir is fairly low and below the height of the thermostat intake hose (or whatever it's called). That's where the level usually sits but perhaps I should fill it right up initially so it can get to the stat and flood that area. (I'll post a picture in a minute). After putting 40 litres of antifreeze in I ran out, but I should have a delivery of more tomorrow.

 

The coolant normally sits at that level but how does it get to the thermostat if it's below the height of the bent hose at the top of the picture? Or is that just a return hose from the stat to the reservoir?

Edited June 20, 2019 by blackrose

[Mad Harold]

I have severely cursed my direct raw water engine cooling system on several occasions, (cleaning intake strainer,water filter,flushing sediment out of the water jacket) but reading your post, perhaps my system is  not so bad.!

 

 

 

 

.

[Tony Brooks]

First of all that hose is the feed form thermostat to the header tank and secondly if the water pump is not full of air I am confident that it would reduce enough flow to pump water through that hose, from thermostat to engine. Remember the temperature sensitive part of the thermostat hangs down  into the top of the head so that is probably covered in coolant.

 

When you refilled did you start with the skin tank bleed point open and only close it once coolant was running out of it? If not you may have driven air into a bow in the main skin tank to engine pipework.  I think, as others have said, cap off and the lost of bending and squeezing of the large skin tank hoses. With a  bit of luck it will eventually make a large glug and the header tank will empty as a bubble of air finds its way out. I would spend most time on the hose going to the top of the skin tank.

 

When you were trying to bleed the calorifier and  also getting air out of the large hoses were you revving the engine, if not try that. I would suggest to about 1500 to 2000 rpm.

[blackrose]

2 hours ago, Mad Harold said:

I have severely cursed my direct raw water engine cooling system on several occasions, (cleaning intake strainer,water filter,flushing sediment out of the water jacket) but reading your post, perhaps my system is  not so bad.!

 

 

Every system has its disadvantages, but in general a closed loop cooling system is going to be better on shallow canals and weedy rivers than any raw water system.

 

Initially mine only had one skin tank when it should have had two, but since I sorted out that problem and added an additional tank about 7 years ago I haven't had any issues until now. This is probably my own fault because I used a wetvac to pull all the old antifreeze out and sucked air deep into the system. I'm just hoping I haven't dragged crap from the bottom of the skin tanks into narrow cooling ports and blocked them up.

1 hour ago, Tony Brooks said:

First of all that hose is the feed form thermostat to the header tank and secondly if the water pump is not full of air I am confident that it would reduce enough flow to pump water through that hose, from thermostat to engine. Remember the temperature sensitive part of the thermostat hangs down  into the top of the head so that is probably covered in coolant.

 

When you refilled did you start with the skin tank bleed point open and only close it once coolant was running out of it? If not you may have driven air into a bow in the main skin tank to engine pipework.  I think, as others have said, cap off and the lost of bending and squeezing of the large skin tank hoses. With a  bit of luck it will eventually make a large glug and the header tank will empty as a bubble of air finds its way out. I would spend most time on the hose going to the top of the skin tank.

 

When you were trying to bleed the calorifier and  also getting air out of the large hoses were you revving the engine, if not try that. I would suggest to about 1500 to 2000 rpm.

 

Thanks Tony. I didn't bleed the skin tanks while the engine was running, but I've checked both tanks and coolant comes out both bleed valves so I'm confident they are full.

 

I'll try your suggestion of revving the engine a bit harder and bleed the calorifier, etc, again.

[Cheshire cat]

When you took your thermostat out it should have been at least half submerged in water. If it wasn't you should have topped it up via the thermostat housing. If the waterpump empeller isn't surrounded by water there is not going to be any water flow. It's got nothing to pull through.

[blackrose]

There was coolant under the thermostat but i think it was below the depth of the stat itself. I'm going to wait until more antifreeze arrives tomorrow, top it right up and try again.

[Sea Dog]

2 hours ago, blackrose said:

This is probably my own fault because I used a wetvac to pull all the old antifreeze out and sucked air deep into the system.

I doubt this BR - the purpose of draining down is to remove all of the old coolant, so a properly drained system will be full of air even without a wet vac. Even if you've got a whole extra bunch of fluid ounces out, you won't have made it worse.

[Tony Brooks]

3 hours ago, blackrose said:

 

Every system has its disadvantages, but in general a closed loop cooling system is going to be better on shallow canals and weedy rivers than any raw water system.

 

Initially mine only had one skin tank when it should have had two, but since I sorted out that problem and added an additional tank about 7 years ago I haven't had any issues until now. This is probably my own fault because I used a wetvac to pull all the old antifreeze out and sucked air deep into the system. I'm just hoping I haven't dragged crap from the bottom of the skin tanks into narrow cooling ports and blocked them up.

 

Thanks Tony. I didn't bleed the skin tanks while the engine was running, but I've checked both tanks and coolant comes out both bleed valves so I'm confident they are full.

 

I'll try your suggestion of revving the engine a bit harder and bleed the calorifier, etc, again.

That is not what I meant to say. When you initially filled the engine did you do it with your skin tank vents open? If not then you may well have pushed some air into a bow in a pipe somewhere so both tanks could now be full but some air may be in a pipe, especially as you have two skin tanks. I 32would not bleed the skin tanks with the engine running, it just might suck in air so not worth the risk but if needs must I doubt it will do  any harm. I meant take the filler cap off, near;ly fill the header tank and the rev the engine for a while.

[bizzard]

Its often best to blip the throttle up high and down every couple of seconds. This tends to sort of rock any trapped air in loops or bows back and forth and up and over and out.