Overheating

[d21demon]

Well Im stumped!
The other day I drove home from being away for a week for work, and the old girl started to drive a bit erratically. After checking the temp gauge, she was running about half way, when usually she doesnt get to a quarter.
Since then I changed the thermestat,no change, so replaced the radiator cap, still hot. So I checked to see if anything was coming through the top hose by sqeezing it then releasing it, no surge of coolant and the hose was very hot to touch after only a few minutes running. So I inspected the water pump, nothing untoward but I replaced it anyway. Its still running hot and doesnt seem to have anything moving through the top pipe.
Before I go and buy a new radiator, does anybody have any other suggestions I could try first?

 

[Old.Tony]

Sounds like a blockage. Tried flushing it? How about filling it (cold), crank the engine over for 15 seconds, then fill some more. Does any get in that top pipe after this?

 

[SOLID D22]

As old tony said try flush the engine first and the radiator also.

 

[d21demon]

Thanks for the response guys, so far Ive dropped the coolant three times to replace parts, put radiator flush through it twice and even put the hose in hoping to budge anything while I had the pump off. I'm thinking its either a blockage in the engine or a stuffed radiator, but how do I tell which ?

 

[Old.Tony]

In an older motor you could look in the radiator cap and see the cores, but the manual for the D40 seems to show the cap is offset to the cores, probably because half of the radiator is plastic.

If you can see the cores in yours, do they show any signs of corrosion? What colour was the water that came out the first time? There might be rust blocking the radiator cores, particularly if she's been around the block a few times.

That doesn't explain why you don't get water moving in the top hose though - for that, you'd have to wonder if the block/head had something stopping the coolant from getting through. I'd first suspect the thermostat, being either faulty or installed backwards.

You'd have to doubt that the block/head would be blocked up. You'd have seen something when you pulled the water pump, like excessive corrosion.

 

[Pinelli]

I've just been told that the viscous fan hub on my D21 has started to go, and mine starts to heat up a little at idle or low speeds. Something else to check?

Here's a question: Does the temp drop again at speed or with revs?

 

[Pinelli]

Something else - Are you losing water? Could be the radiator cap or overflow bottle. If you've got the original overflow bottle it could be as completely trashed as mine was, it may not allow water to flow back into the radiator when pressure drops as it cools.

 

[d21demon]

Thanks for the help guys. After taking in your suggestions and still not comming to any conclusions I decided to take it to the local specialist. After he had a good look at it, he reckons the old radiator is completly stuffed and its time for a new one, his main concern was that it might be the head gasket or even the head gasket but luckily it was none of these. So the new radiator comes on monday and he's going to give the whole system a good clean out just in case theres still a blockage in there somewhere.

Again thanks for the help guys it's nice to know your all there to give a hand.