for all those 'in the know' about ECU's

[mike74]

I've got a quick question for you guys. I've had an intermittent issue with losing coolant through the expansion tank, usually once the engine is pretty hot & then driving slowly or switching off soon after. The temperature needle has only moved off-centre once & even then only by 1mm or so. I replaced the radiator cap yesterday with a blueprint one (the thermostat's next) & noticed the car feels a lot smoother & 'perkier' too while giving it some. So...does the ECU start to pull timing/dump more fuel after it gets past a certain temperature; bearing in mind the gauge is showing consistently the same reading? It definitely feels different to drive but I can't see the ECU tweaking things at what appears to be normal engine temperature...unless the coolant wasn't being circulated correctly before. Any thoughts? /Hmmm
muchas gracias amigo's

mike

[Nick Mann]

Shouldn't make any difference IMO.

One small thinking point, though - the dash temperature sensor is seperate from the ecu temperature sensor. They are both in the same place though, so temperatures readshould be the same.

[mike74]

yeah, thats what i thought too but wasn't sure. it definitely feels different but, could be a placebo i spose. maybe i should go & wash it & get even more powah out of it :)

[Turbo_Steve]

Could be Placebo.

However, the ECU will have a temperature compensation table of some kind, though usually just up to "operating temperature" rather than having a hotter scale as well.

The gauge on the dash only basically has 3 positions:

Cold
Ok
New Engine

It's the most innacurate thing you've ever seen.

So if your ECU thought the car was running cold, it might have been a bit rich.
It would have to be a fairly small difference, though.

What is also possible is that your water system is flowing a lot more freely, which means less resistance at the water pump, which means a more responsive engine.

It's amazing how big a difference little things like this can make.

[mike74]

hmm that makes sense, i hadn't thought on it that way before. ill hopefully get the 'stat changed over this weekend so ill report back with my findings (if any).
thanks for the input guys, its nice to know im not going bonkers :whistle:

[The Vee]

Coolant temp is very important to the ecu as Steve has outlined. If your pressure cap has altered the running temp then it is quite possible it has altered the way the car runs. As stated, the ECU temp sensor is a lot more sensitive than the rough guide on the dash!

[mike74]

I'm totally looking forward to changing out the thermostat if the cap had that big an effect on its running. It most definitely runs & sounds different now :)
I should have a better idea if its had any real-world effect or not once I refuel & work out my consumption next week...watch this space...

[Patryn999]

I'm not enturely sure about this ECU, but its generally done that if the ECU senses a temperature greater than a set point it will start over-fueling in an attempt to cool it down a little.

An increased engine temp can also cause detonation, which will make the ECU retard timings.

Not saying these happened but if you do get something out of it this may be an explaination.

[Louis]

Also check for leaks and check the waterpump, how much water are you loosing (per day, per week,), what is the mileage?

[mike74]

There's no leaks around the engine at all & the coolant/oil aren't contaminated. Mileage of the car is about 47k miles (or thereabouts). Water loss varies as it only used to spit it out when the expansion bottle was at the correct level then, engine ran hard & allowed to idle or switched off while hot. It was DEFINITELY coming out of the overflow though & nowhere else. With the old cap in & engine hot or cold you could squeeze the top radiator hose & see the water level in the expansion bottle rising. With the new cap on this has stopped so pretty sure the old cap was a major factor. As I said, I've still to change out the 'stat & see if anything else 'improves' but I've convinced myself there's nothing sinister going on...all being well. Oh, the heaters work ok too :)

[mike74]

I was going to post up last night to say how well the car had been going since changing the thernmostat & cap just over a week ago....until I went out to the car last night after work to find a 5" long crack on the top of the radiator & the WHOLE engine covered in coolant!!! :censored:
When I was walking away from it in the morning I thought I heard a funny 'scooshing' noise coming from it but couldn't see anything dribbling below it so thought I'd check it that night. Just as well I did. Thankfully it only seems to be leaking after the engine is switched off so we got it home without any problems & dropped it at the garage first thing today. It was going in for its MOT tomorrow afternoon anyway so they've got it to sort as well now.
On a lighter note, when it WAS working it seemed to be a lot happier with itself. It felt quieter & smoother and can definitely say theres a slight improvement with the fuel economy too. Its only improved by 1-2 mpg but thats not bad seeing as it only cost me the price of the parts! :)
Unless of course I'll have to change the radiator every week or two :(
F*****G cars!!

[HPRULZ]

Havent seen any mention of it in the thread (unless I just missed it been old and short sighted) but there is a pipe attatched to the inside of the lid on the overflow tank, mine used to dump water from the tank because this pipe had become old and soft and loose and more often than not detatched from the lid.
It stopped doing it when I replaced the pipe so it doesnt fall off, might be worth checking when you get your car back.

Kev

[mike74]

The thing is, it hadn't lost any water since I changed the cap so I'm pretty sure that was the main culprit behind it. I guess the extra pressure the new cap generated was just too much for the radiator to hold :(
Even so, I'll give it a check when I get it back, just in case :)

[Turbo_Steve]

Mike, Given your problems it might be worth getting a compression test done, just to rule out a more serious underlying issue.

[mike74]

Would a sniffer test give a definitive answer if the HG is leaking into the coolant or not? There doesnt 'appear' to be anything else untoward happening with it, its hopefully just bad luck the rad's gone now. One of the first things I checked when I found the water was under the oil cap, which was fine. No signs or smells of coolant in there. The thing is that out of our fleet of ageing motors, the Galoon is the only one thats road-legal at the moment so can't afford to have it off the road for too long :(
I'll speak to the garage & see if they can do any checks while its there with them. Unless they find or suspect something untoward, I'll go with the sniffer for now & keep a CLOSE watch over things.
Many thanks for all the reply's though peeps, much appreciated :)

[Turbo_Steve]

TBH it may be worth asking them to compression test it anyway? I doubt it will cost much (pain in the neck taking the inlet manifold off...but that's all).

The problem with sniffer tests on turbo'd cars is (IMO) that your coolant system may only be overpressurising when you're on flat-out-red-hot-maximum boost for any period of time.

All that being said, if you're on a budget at the moment, you could just change the rad, keep a close watch on the coolant and take it easy until times are a bit more convenient.

[mike74]

Yeah, I think I'll do that Steve. I've currently got the Galoon in being fixed/mot'd, a Pulsar in to get the new suspension set-up & mot and a mini imminently awaiting an mot too. Not a good time to blow a radiator up! :(
I'll speak to the guys at the garage today to see if they can do the sniffer after fitting the rad & maybe start saving up for a new set of leads & a compression tester for later on in the year. If I'm taking off the inlet to do the compression test I might as well throw in something shiney while I'm at it. :)
Cheers for the advice dude

mike

[mike74]

Well, we picked the car up on Friday night after getting it fixed. No more coolant leaking anywhere or p!ssing out of the expansion bottle! I spoke to the mechanic about getting some tests done on it but he reckoned it was just 'one of those things'. If the cooling system was being pressuried then the cap would've unseated first or, failing that a hose would've split; not the radiator. Anyway, everything appears to be working fine n dandy now but I'll obviously keep a close eye on levels etc for any sudden change over the coming weeks. It also got a new MOT done then too with only one advisory on it! /Hmmm
The only thing that was picked up was track rod ends (inner & outer) which were already waiting to go on the car so I class that as a clean bill of health :2thumbsup
One thing I've noticed is that the car seems to be running a little bit cooler, according to the gauge & I might be imagining things but the mpg appears to be better too. I'll monitor this over the next couple of weeks & give a definitive answer as to whether all this has had any measurable impact to the car.

Thanks once again to everyone, muchas gracias :)