Over heating when towing

I'm just home after an outing with my youngest daughter towing trailer behind my Td5 year 2000. I have been loosing a small amount of water for some time now, and have not been able to find a leak, so have been topping up the header tank on a regular basis.

I only use the vehicle twice a week max, so clearly not doing many miles. I had a new oil cooler, radiator, inter cooler and thermostat about twelve months ago. So I think that the rad is not the problem.

The heater has not been working for a while and I have been planing to overhaul the matrix, which I had suspected could be the source of my leak and possibly the problem with my heater.

However, during my trip today the engine overheated going up a long gradual incline. After the engine had cooled down, about three hours, I filled the system and headed home. I did not remove the screw on top of the top hose to make sure that the system was full and free of air - my mistake.

On the way home the heater started to send out hot air, much to my surprise, but after a couple of minutes the air blew cold and the temperature started to rise whenever I came to another incline. When the engine was not under power the temp dropped down to normal again.

The car had been running really well up until the overheating and continued to run well after the temperature had regularised, after the system was replenished.

Any suggestions would be most welcome.

Sounds like the thermostat is not working properly.

When mine was showing the same signs as yours a new Rad was required.

Flush your radiator.... I think your problem is with that

Also get some uv dye.

Is it a plastic and ali rad?

zeaphod said:

Sounds like the thermostat is not working properly.

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I hope that's all that it is. The thermostat was replaced with the other work after the oil cooler burst and filler the water system with oil. Thanks for your thoughts

flat said:

Also get some uv dye.

Is it a plastic and ali rad?

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What is the UV dye for? Will this show a trace of colour where the leak is emanating from? And, the new rad was a standard replacement which I suspect was aluminium. It certainly did not feel like plastic. Thanks for your response. I will try and find where I can get some UV dye, which I as gum will come from my local Auto repair shop.

Landyfox said:

Flush your radiator.... I think your problem is with that

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Thanks for your suggestion. It's a fairly new rad, but I suspect that when the oil cooler broke some of the oil that rushed into, and filled the water cooling system, might still remain. I'll give it a go.

Heater not blowing hot should be shouting all sorts of scary things at you. Heater should work even if the rad is blocked and stat is duff. If it not blowing hot it's usually because there isn't enough coolant in the system.

Could be simply an air lock so start by making sure it's bled properly and go from there.

blue beasty said:

Heater not blowing hot should be shouting all sorts of scary things at you. Heater should work even if the rad is blocked and stat is duff. If it not blowing hot it's usually because there isn't enough coolant in the system.

Could be simply an air lock so start by making sure it's bled properly and go from there.

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BB... when my radiator was blocked, heater emitted very little heat. Process of elimination

Alan Crossley said:

What is the UV dye for? Will this show a trace of colour where the leak is emanating from? And, the new rad was a standard replacement which I suspect was aluminium. It certainly did not feel like plastic. Thanks for your response. I will try and find where I can get some UV dye, which I as gum will come from my local Auto repair shop.

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yep - it flouresces (spelling??) under a UV light and helped me track down 2 pin prick leaks that the pressure test highlighted but that i couldnt find.
once its in the tank though its there for ever which is good or bad depending on your opinion

That sounds like a very good idea. One slight problem might be my Polish mechanic, who's very good but might not be up to speed with UV light technology. That might sound disrespectful, but in honesty he's an honest, down to earth mechanic who repairs components, rather than simply replace them with new.

I'm going to to talk to him tomorrow and see what he says. Thanks again for your help.

Heater running hot and cold seems like air in system to me. Sort out leaks first then burp the air out.

blue beasty said:

Heater not blowing hot should be shouting all sorts of scary things at you. Heater should work even if the rad is blocked and stat is duff. If it not blowing hot it's usually because there isn't enough coolant in the system.

Could be simply an air lock so start by making sure it's bled properly and go from there.

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Don't like the sound of the first part of your message, but I'm going to get a new expansion bottle top, which I understand could be leaking. There is a damp patch on the foam insulation immediately above the bottle but it doesn't look like it's that much fluid.

I'm off to the garage tomorrow to see if they can pressure test the system to see if there is a leak and I'll take it on from there. Thanks for your suggestion- if not the first element!

mick the builder said:

Heater running hot and cold seems like air in system to me. Sort out leaks first then burp the air out.

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Yes Michael, I've just posted a rely of that nature and, after I have had a pressure test, if I find a leak, I'll take it on from there. I'm also going to order a replacement expansion tank top, in case that's not standing up to the high pressure. Thanks for you'r thoughts

Landyfox said:

BB... when my radiator was blocked, heater emitted very little heat. Process of elimination

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That sounds like the introduction to a plan being formulated. Thanks for your response

Alan Crossley said:

Yes Michael, I've just posted a rely of that nature and, after I have had a pressure test, if I find a leak, I'll take it on from there. I'm also going to order a replacement expansion tank top, in case that's not standing up to the high pressure. Thanks for you'r thoughts

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Only my mum and the police call me Michael.

Okay Michael it is then. After I have sorted out the leak, you can instruct me in how to "burp the air out"

Best thing to do is stop towing.

Bobsticle said:

Best thing to do is stop towing.

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Not very helpful Mr Bobsticle, especially from a nearly Mancunian member!