TD5 Cooling system query.

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pabroon74

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17
Hi folks.

I have a question that requires the forum's collective wisdom: I've had my disco 2000 TD5 for just over six months with what I assume has been the normal amounts of botheration, ACE thingy going arse up, injector loom disintegrating etc. But, recently, when pressing on, the car is over heating - cold water is coming out from somewhere (no idea where) and when I loosen the cap on the expansion tank hot coolant spurts from the over flow.

I've flushed it all out as best I could, couldn't find a drain plug so howked off the bottom pipe but it's still at it.

I suspect it's blocked some where, but has anyone had this before? Also, this may or may not matter: when I set off of a morn, the car warms up to about a quarter on the temp gauge then stays there for a good while. Once I get on the bypass and open up a bit up shoots up to the half way mark, if I stick to the town it can stay at the quarter mark indefinitely.

I throw myself on the conjoined wit of the forum, please be gentle with me.

Thanks in advance.

Paul.
 
I recently changed by header tank cap and it solved all my cooling issues. Stopped leaks, stopped the coolant disappearing then reappearing when i opened the cap, stopped the pipes bulging and staying like that even when the engine cooled down.

It has a pressure release system on it and my old caps system was obviously broken.
 
I can't work out how to use the multi quote button so see below for a few thoughts / pointers:
pabroon74 said:
Hi folks.

Snip.. But, recently, when pressing on, the car is over heating - cold water is coming out from somewhere (no idea where) Check the water pump 'P' gasket, it's on the nearside of the engine towards the rear, you may also be able to see a leak from underneath the engine. and when I loosen the cap on the expansion tank hot coolant spurts from the over flow. Is this when the coolant is hot or cold?

I've flushed it all out as best I could, couldn't find a drain plug so howked off the bottom pipe but it's still at it. There's a drain plug on the steel coolant pipe that runs left to right under the engine, the pipes about 25mm dia and the drain plug is 13mm

I suspect it's blocked some where, but has anyone had this before? Also, this may or may not matter: when I set off of a morn, the car warms up to about a quarter on the temp gauge then stays there for a good while. Once I get on the bypass and open up a bit up shoots up to the half way mark, if I stick to the town it can stay at the quarter mark indefinitely. This is normal, the thermostat only opens fully when the engine is running above 1500 rpm

I throw myself on the conjoined wit of the forum, please be gentle with me.

Thanks in advance.

Paul.
Click to expand...
Have a read up on the threads on here about the cooling system; I suggest you eliminate any leaks, replace the expansion cap and change the thermostat first. Hopefully that will cure it - if not come back and read up about over-pressuring and the dreaded head gasket.

HTH
 
Hi folks and thanks.

I'll avoid the 'dreaded head gasket' chat for now. We howked it apart on Monday, the thermostat was a bit clarty with pipes bulging - it may have been partially blocked.

Ordered a replacement and replaced pipes with silicon jobs I've had for a while. Also replacing the intercooler because it was in a poor state.

See how that goes.

Ta

Paul.
 
For the non techies among us who have always believed a thermostat is a component which sensors the temperature of the coolant and therefore controls the flow of the coolant between engine and radiator.. how does it know the engines RPM is 1500 + also not to open fully at any other time but only then :confused:
 
discool said:
For the non techies among us who have always believed a thermostat is a component which sensors the temperature of the coolant and therefore controls the flow of the coolant between engine and radiator.. how does it know the engines RPM is 1500 + also not to open fully at any other time but only then :confused:
Click to expand...

This is a good question.

I thought it (the thermostat) was sticking and only opening when the flow reached a certain pressure. I don't know of any other car that warms up to a certain point, stays there for an unspecified time then shoots up to the proper temp.

Seems to me, there is another controlling factor in there somewhere.

Paul.
 
discool said:
For the non techies among us who have always believed a thermostat is a component which sensors the temperature of the coolant and therefore controls the flow of the coolant between engine and radiator.. how does it know the engines RPM is 1500 + also not to open fully at any other time but only then :confused:
Click to expand...
I only know about it from what I've read in Rave:
[FONT=&quot]Thermostat housing[/FONT]
[FONT=&quot]A plastic thermostat housing is located behind the radiator. The housing has three connections which locate the radiator bottom hose, top hose and coolant pump feed pipe. The housing contains a wax element thermostat and a spring loaded by-pass flow valve.[/FONT]

[FONT=&quot]Thermostat - Main valve[/FONT]
[FONT=&quot]The thermostat is used to maintain the coolant at the optimum temperature for efficient combustion and to aid engine warm-up. The thermostat is closed at temperatures below approximately 8[/FONT]2[FONT=&quot]C (17[/FONT]9[FONT=&quot]F). When the coolant temperature reaches approximately 8[/FONT]2[FONT=&quot]C the thermostat starts to open and is fully open at approximately 9[/FONT]6[FONT=&quot]C (20[/FONT]4[FONT=&quot]F). In this condition the full flow of coolant is directed through the radiator. The thermostat is exposed to 90% hot coolant from the engine on one side and 10% cold coolant returning from the radiator bottom hose on the other side. Hot coolant from the engine passes from the by-pass pipe through four sensing holes in the flow valve into a tube surrounding 90% of the thermostat sensitive area. Cold coolant returning from the radiator, cooled by the ambient air, conducts through 10% of the thermostat sensitive area. In cold ambient temperatures, the engine temperature is raised approximately 1[/FONT]0[FONT=&quot]C (5[/FONT]0[FONT=&quot]F) to compensate for the heat loss of 10% exposure to the cold coolant returning from the radiator bottom hose.[/FONT]

[FONT=&quot]By-pass flow valve[/FONT]
[FONT=&quot]The by-pass flow valve is held closed by a light spring. It operates to further aid heater warm-up. When the main valve is closed and the engine speed is below 1500 rev/min, the coolant pump does not produce sufficient flow and pressure to open the valve. In this condition the valve prevents coolant circulating through the by-pass circuit and forces the coolant through the heater matrix only. This provides a higher flow of warm coolant through the heater matrix to improve passenger comfort in cold conditions. When the engine speed increases above 1500 rev/min the coolant pump produces a greater flow and pressure than the heater circuit can take. The pressure acts on the flow valve and overcomes the valve spring pressure, opening the valve and limiting the pressure in the heater circuit. The valve modulates to provide maximum coolant flow through the heater matrix and yet allowing excess coolant to flow into the by-pass circuit to provide the engines cooling needs at higher engine rev/min.
[/FONT]​
[FONT=&quot]HTH[/FONT]
 
Now it's very clear, the three paragraphs from Rave explains all. :)

So The 1500+ rpm has nothing to do with the Thermostat as stated but the gizmo called By-pass flow valve, which to some may seem that heater warm-up times may have been an issue in the development of the engine.
 
the bypass flow valve is part of the thermostat and it's linked to the main valve, it works in conjunction with it to keep an aproximately steady operating temperature of the engine and the matrix by releasing/restricting the flow based on the coolant's temp and the pressure from the pump, here is how the thermostat works http://www.landyzone.co.uk/lz/3108995-post8.html
 
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That image is useful, the diagrams on RAVE with the wee arrows showing flow are hard to make out. What I can't figure out is, the arrows on the RAVE diagram aren't truly accurate, they show the flow direction coming from the rad - to the thermostat - and on through the bypass pipe, when if the engine is fully warm there would be no flow. While warming up those arrows (in the RAVE diagram) should be reversed.

Here's where I am now, we swapped out the thermostat but it made no difference - what we have noticed is, its when the engine gets up to temp (when the gauge goes up to half) it begins to leak.

The leak seems to be coming from the front somewhere (its coming through all that annoying plastic beneath the rad etc.)

So the leak must be coming from the radiator right? If no fluid circulates through the rad while the engine warms there would be no pressure in it... I can't figure out what to check - other than the radiator.

Due to go to Arran on Friday in it, I can't get five people on my motorbike so I'm beginning to wonder...

Much obliged for the all the info and help.

Thanks

Paul.
 
pabroon74 said:
The leak seems to be coming from the front somewhere (its coming through all that annoying plastic beneath the rad etc.)
Click to expand...

So this sounds like the old chestnut where the screws that hold the fan cowl onto the rad self-tap (yes, you read that right) into the end chamber of the rad, and the thin wall around the screw is susceptible to cracking over time.

Easy to check by whipping off the cowl and see if coolant ****es out the supposedly blind screw hole, and easy to fix with plumbers muck or PTFE tape or whatevs.
 
Thermostat and furred up rad, i spoke to a guy when mine had simular symptons, i was told that the rads fur up with age and need flushing regular, i got a new rad and problem went away, although summat else comes along:scratching_chin:
 
Last edited:
discodrivercumbria said:
Thermostat and furred up rad, i spoke to a guy when mine had simular symptons, i was told the rads fur up with age and need flushing rewgular, i got a new rad and problem went away, altough summat else comes along:scratching_chin:
Click to expand...

Oh dear, should have been ok if you have always changed your antifreeze with the correct quantity as required.
I've never had an issue, I believe because the vehicles antifreeze is replaced when required as per the products/ vehicles specification... Import and with alloy engines.
Antifreeze chemicals could retain their basic properties indefinitely, but corrosion inhibitors are gradually used up, and must be replenished from time to time, hence the requirement to replace antifreeze.
Ive be using OAT in my disco for the last thirteen years so is great that replacement is now five years, and still original rad and thermostat.
 
discool said:
Oh dear, should have been ok if you have always changed your antifreeze with the correct quantity as required.
I've never had an issue, I believe because the vehicles antifreeze is replaced when required as per the products/ vehicles specification... Import and with alloy engines.
Antifreeze chemicals could retain their basic properties indefinitely, but corrosion inhibitors are gradually used up, and must be replenished from time to time, hence the requirement to replace antifreeze.
Ive be using OAT in my disco for the last thirteen years so is great that replacement is now five years, and still original rad and thermostat.
Click to expand...

youve had yours from new, ive only had this 2 1/2 year, so i got what others have left behind!
Also a lot of your qoutes to this and others are your exsperiance of owning a motor from new, many like myself have only had it short while or a recent purchase, so your answer is a bit zoid!
 
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Thanks for the replies.

I'll check the self tapping screws on the rad (that is a bit of a daft idea...)

I think its stopped leaking, although that could be because the coolant is now mostly Radweld - which I appreciate isn't an ideal fix even if it does fix the initial problem.

;-)
 
I had the same issue on my TD5 about 5 years ago. Turned out to be a head gasket issue. Basically, the gasket failed from the piston head to a coolant port thus compressing the expansion tank forcing coolant out of the tank. It took me about three weeks to reach the conclusion it was the head gasket. Tried new tank cap which didn't work. Fortunately, my cylinder head wasn't cracked and so it just needed a new head gasket. I've had no problems with it since. erm.... well no cooling problems :)
 
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