2.8 engine: Air in the Cooling system? Need help! - Defender Source
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  #1  
Old December 8th, 2008, 09:27 AM
Santiago
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Santiago Gigola
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2.8 engine: Air in the Cooling system? Need help!

HI,

I have a 2.8 HS International engine adapted to an originally Td5 Defender and until yesterday I had not had any problems with engine temperature. Yesterday I took it to the mountains and after a very long and steep section (kms and kms of climbing at 20 to 30kms per hour, the final part in 1st and 2nd low gear because it was VERY steep terrain) the engine water temperature got up to 97C (207F).

I undertsand this temperature may still be OK for this engine (according to the PDF version of the 2.8HS engine manual the maximum oprating temperature is 102C or 215F) but I had never seen it rise so high so I am a bit worried.

I had recently changed all the cooling fluid in my Defender 110 trying not to leave any air bubbles in the system. This morning I decided to check if this was OK to try to understand if the cause of the high temperature yesterday was related to air in the system.

I unscrewed the disaeration plug (original black plastic plug) located in the upper part of the thermostat housing and found that it was not filled with water/collant up to the top but instead I just found air.......

Is this correct? I suspected it was not so I then usncrewed the cover of the cooling system expansion reservoir. This made water come down from the expansion reservoir (I have the original Td5 cooling system expansion resrvoir and it is located slightly higher than the termostat housing), displacing the air out of the thermostat housing. I then screwed the black plastic plug on top of the thermostat housing back in and filled up the expansion reservoir to level.

Then I run the engine , water level in the expansion resvoir raised about an inch while engine was running.
The thing is after I let the engine cool down completely I found the level on the expansion tank did not go down to level again.

I checked again unscrewing the disaeration plug on top of the thermostat housing to find that it was filled with air again!!!!

What am I doing wong?
Is it OK to have the thermostat housing filled with air instead of water when you remove the disaeration plug?
If not, how do I get rid of this air?
Could this air be affecting the cooling in my engine?
The only other difference in my engine since last summer is that I installed an aftermarket AC system during the winter and the AC radiator is located in front of the engine radiator. Could this be causing the decrease in cooling?

I will really appreciate any help since I need to travel about 1,200kms tis week and it is summer down here, with themperatures in the order of 95 to 100F.


Thanks in advance!
Cheers,
Santiago

Follow-up Post:

I just unscrewed the cover of the expansion reservoir and the water level instantly fell to where it should be (half the expansion tank).
Does this mean that the valve in the cap of the expansion reservoir is not working properly and letting air in and out asi it should be?

Help!
Cheers,
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  #2  
Old December 8th, 2008, 12:49 PM
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pendy
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jim pendleton
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You need a larger radiator. I explained this to you in detail many months ago when you inquired about intercoolers. The 300 tdi and/or the td5 arrangements are not up to the challenge. More power output equates to larger cooling demand. And the new gearing you are running in your truck does not help matters either. More load equates larger EGT figures which adds to the cooling demand.

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  #3  
Old December 8th, 2008, 05:22 PM
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John B.
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Is there not a small hose from the top of the radiator to the expansion tank? This is meant to ensure all the air goes to the expansion tank.

It does sound like the expansion tank cap is not working. It should let air in and prevent a vacuum.

As to the temperatures. What are you using for a fan and shroud.
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  #4  
Old December 9th, 2008, 12:28 PM
Santiago
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Santiago Gigola
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Pendy,

I believe you, just that I had not had any problems until now. Not that I have really had a problem so far but it looks that with the two mods I've introduced (aircon radiotor in front and higher gearing) things may be a bit hotter this summer and I will have to be careful with Temp.
Thanks for the comment on the influence that my new gearing may have on cooling, I had not thought about it

Yesterday I tested my Defender 110 at constant 68 to 74 mph, along a slight to moderate uphill slope and with 90 degrees F temperatures outside. Engine water temperarture stabilised at 201F while going up hill (for many kilometres) and quickly fell to about 194F when heading downhill.

Depending on the results after this summer I may decide to go the Pendy radiator route next year. I will eventually contact you by private mail if I decide to try one of your radiators.

Thanks for your comments.



Red 90,

a) Yes there is a hose that goes from the radiator top to the expansion tank, and also a 3 way connector that connects to another hose that goes to the thermostat housing (I think, not sure about the last).

b) Expansion tank cap: YES!
I tried an old receipe yesterday: I put the expansion tank cap in vinegar for a few hours yesterday to remove any salts that could eventually be preventing the valve in the cap from working properly. I then washed it thorougly in water and put it back on. I took the truck for a long and +/- hot ride and after returning and letting the truck cool down it worked! Water level came down to normal. I interpret that, as you suggested, it was the expansion tank cap that was botherin!
THANKS Red90!

c) the fan I have is (I think) the one that came with the 2.8 engine in the South american Ford Ranger. I have no shroud . I cut a little bit of the Defender 110 Tdi plastic fan shroud and put it on top just to prevent hitting your fingers with the fan but the entire 300Tdi shroud does not fit.
I think it has to do with the fact that my defender was a Td5, not a Tdi. I understand that it fits if you install the 2.8 engine in a 300 tdi Defender but I am NOT SURE.

Do you think the lack of a shroud could be partly responsible for the relatively high temperare I got the other day while climbing a steep slope at low speeds?
I do nt exactly understand the function of a fan shroud, it helps cooling when travelling at low speeds?

Thanks for your comments!

Others: feel free to tell me your thoughts, I want to learn!

Cheers,
Santiago
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  #5  
Old December 9th, 2008, 02:51 PM
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John B.
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Yes, a lack of a shroud is night and day. An axial fan will do very little unless it is contained and ducted tightly to the radiator. It is basically just recirculating air in the engine bay at the moment and doing very little to get air flowing through the radiator. The air goes through the fan hits the engine, circles around the outside of the fan and goes through the fan again. There is no reason for the air to go through the radiator due to the fan. I'm sure a proper shroud would fix all the overheating problems immediately assume the fan clutch is working properly.

This is a very important step in making a fan work and is overlooked by many people.
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  #6  
Old December 9th, 2008, 03:23 PM
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jim pendleton
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I agree a fan shroud is very important!
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  #7  
Old December 9th, 2008, 08:26 PM
Santiago
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Santiago Gigola
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Red 90/Pendy: I will get moving on this immediately.
Any suggestions on how to go about?
Modifying the 300Tdi one or the Td5 one?
Having one built on purpose?
Any clue?
Maybe I should check the one on the 2.8 F Ranger and try to adapt one.

THANKS!


Cheers
Stgo
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  #8  
Old December 9th, 2008, 08:48 PM
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At slower speeds I can see the value of the fan.......but at speed does the fan really add much to cooling or is it mostly from induction??
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