156 2.4jtd overheating -but why? - Alfa Romeo Forum
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(Post Link) post #1 of 6 Old 22-06-10 Thread Starter
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Hmmm 156 2.4jtd overheating -but why?

Hello, I have tried searching for related threads, but so far haven't been able to find any answers. So I am hoping someone may be able to offer an opinion on my problem. Here is the history up to now:

During winter, no overheating issues noticed.
During Summer, when on motorways, I cannot get above 70 without overheating. Local trips no problem, but yesterday’s trip to Wales and back was not enjoyable. I had to de-clutch on the down slopes so I could get the engine cool enough to make it up the next slope. Even doing 50mph on a gentle upwards slope was enough to start the needle's steady, but determined crawl towards the 3/4 mark.

Fans are cutting in just before needle reaches 3/4 mark on temp gauge, and they do cool the engine quite quickly if the car is standing still. So I believe water pump, thermostat & radiator(?) are okay.

2 different thermostats tried -same symptoms- & I did have the car looked at last Autumn by a local reliable garage. They could not find a clear fault. Water pump tested good by them (and it is less than 2 years old anyhow). Cooling system flushed, but fault persists.

ECU re-tuned by Angel Tuning a couple of years ago, so engine could be expected to produce a bit more heat, but not by the extremely tame way it has to be driven right now.

The radiator looks okay, but I may need a closer look. The local garage thought it was alright when they looked at it last October. Now it is Summer again, and I have been on the motorway, then the problem rears its ugly head again. I notice that some of the lower fins are bent on the radiator, which will restrict the airflow a bit, but this is only on the lower part of the radiator. Higher up they look fine.

I am wondering if there could be an issue with the oil cooler? I'm not sure which direction to go in here. Any ideas?
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The tune will make your car run hotter when giving it some but whilst idle it should be the same. You have guessed the key issues correctly and changed the most simple first! I recon you are on the right lines with the rad. They are known to degrade over time. You don't say how old your 156 is but if its early ish i'd say its rad time. Water pumps are an issue on the JTD currently lasting about 50-60K (check the sticky thread at the top of the 156 section). But this is more related to the bearing. I've seen thread on here about the impellors detaching but I don't think its common. Do the rad as its a fairly easy swap out. The waterpump is a cambelt job so i'd leave that until you've rulled out everything else. Check your hoses when hot for over pressure as it could be a headgasket on the way but usually you get oil in water or vise versa so check the oil cap and water expansion tank. I have heard of the expansion caps on other cars playing up and causing over heat issues so that is another possiblity but not heard of this on alfas.

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I has exactly the same symptoms on my V6 156.
Afraid to say it was the water pump.
Around town and low speed the pump could flow enough water but on the motorway at 70 plus the pump impeller was slipping on the shaft under the extra load and the water was not flowing through the rad fast enough to keep up with the heat produced by the engine so she got hotter and hotter. The only option was to slow down or stop for a while or (what I did!) was turn the heating up to full and the interior fan on full to effectively us the heater matrix as a second radiator. All windows down of course! It worked well enough to allow the needle to return to the usual 90 deg until I got off the motorway although a bit warm on a sunny day!!

Did this for a couple of weeks till I had the water pump (with, of course cambelt and all idlers/tensioners) done and been no prob since.

Best of luck with yours and dont let it overheat!! EXPENSIVE!
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yep my TS was the same, and it was the waterpump. but mine was more obvious as it was pishing water prolonged driving with it getting hot and running out of water halfway to the garage, twice, killed my oil cooler too. rad was fine though

had my aircon on full which turned the high speed fan on and kept it under control until i got to the garage.

good luck matey
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I hear what you are saying about the water pump, but it is only 8000 miles old (changed with cambelt, etc). Radiator is probably 10 years old.

Blast & hell if it is the water pump -should have left the old one in there. Is there a recognised reliable water pump I should be installing?
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Mine was only 20000 miles old and you could spin the impeller on the shaft with only moderate finger pressure. I was lucky it did not fail completely.It was a plastic bladed one and now its a metal bladed one so (hopefully) should last longer! My rad was brand new so I new it would not be that. Also there was a faint but audible whistle (like a turbo whistle) at low to middle revs but not all worn/broken pumps are noisy.
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