Cooling issue - related to AFM? (L series MPFI)

YouTube · Post by **El_Freddo** » Tue Oct 09, 2007 11:31 am

Hey all.

On a trip to SA last weekend my engine temp has been playing up again. The temp guage will usually sit half way on a trip anymore than 30mins. 4wding at high revs and there's little change (i would expect it to rise a little).

Sometimes on trips of an hour or more the gauge will head towards the red line, more so when on longer journeys. Knowing this i was watching the guage on the trip, as the last return trip saw the temp guage just under the red.

The interesting thing we noted was that as the outside air temp dropped, the temp went up on the trip over. On the way back pushing through the adelaide hills the temp didn't go much past half, on the flats out near murray bridge and tailem bend the temp guage was sitting on about 3/4 fluctuating a little up and down every now and then.

I don't think this is a cooling problem as when tailing a truck or car the temp dropped dramatically. I know the car isn't working as hard but it also wouldn't have as much cool air flowing through the radiator.

I replaced the Oxy sensor before leaving, thinking that my old one from the dead engine was on the way out and causing the car to lean out on cruise. There was no change. My mind has now moved to the Air Flow metre, hotwire model, the old engine pushed some oil up through it (cleaned with carbie cleaner). I'm thinking that this part is only operating properly in a certain temp range. I get really good fuel economy -> got 739km to 65 litres (one tank -> got 65L into a 60L tank!), but think this may be a result of what ever the problem is, even though the engine was rebuilt and installed last easter.

Has anyone had any experience with this? The AFM was second hand when i got it, i was meant to borrow one from a mate if he had a unit to see if there was a change but it hasn't happened yet.

Anyone got any other ideas as to what the problem could be?

Cheers

Bennie

Gannon · Post by **Gannon** » Tue Oct 09, 2007 4:07 pm

I dont think the hotwire maf has a temp sensor in it.
I know the flapper had one, as it measured air flow and then calculated the air mass by factoring in the air temp.
The hotwire measures air mass directly, so it doesnt need to know air temp.

I think

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Tue Oct 09, 2007 9:45 pm

The hotwire AFM has a temp sensor in it you can test it from the pins. If your fuel reg is sticking open that will make it run lean and if your engine fan ,assuming you have one, could be causing an air flow issue at higher speeds if it is locking up

Gannon · Post by **Gannon** » Wed Oct 10, 2007 6:46 am

Hotwire AFM has 5 wires, GND, GND, Power, Singal and Burn off

You havent got your fan wired backwards do you?

YouTube · Post by **El_Freddo** » Wed Oct 10, 2007 9:14 am

Suparoo wrote:Hotwire AFM has 5 wires, GND, GND, Power, Singal and Burn off

You havent got your fan wired backwards do you?

Thermo fan wired correctly, it blows hot air over my hand when near the engine. Not sure about the engine powered fan locking up. Has no shroud though - this wasn't a problem with the other engine (at least til i did a head gasket).

Whats the burn off? And how do i test the temp sensor (should look up manual at this point...)?

So it could be a dodgy temp sensor? I've changed the fuel regulator since this problem has been around, but there hasn't been any change. Anyother way to check this?

Cheers

Bennie

Gannon · Post by **Gannon** » Wed Oct 10, 2007 7:07 pm

There is no air temp sensor. The ecu doesnt need to know the air temp as it already knows the air from the AFM

The burnoff on the AFM is a surge of current for about 1 second to clean the hotwires when you switch off the engine.

Are you sure its just not a coincidence?

YouTube · Post by **El_Freddo** » Thu Oct 11, 2007 2:46 pm

Suparoo wrote:Are you sure its just not a coincidence?

Which part of it?

- The outside air cooling and the engine temp rising? or
- the changing of the fuel reg??

Bennie

YouTube · Post by **El_Freddo** » Wed Oct 17, 2007 1:48 pm

Well I never got around to testing/changing the AFM. Almost cooked ruby scoo monday. Everything pointed to the thermostat or radiator. So dad cut the guts out of an old thermostat and i put that in. Took about 6km to start warming the car up.

Still no change in the temp at speed, it was a much colder day tuesday and the car ran hotter than expected, peaking at 2/3rd of the temp guage.

Out came the radiator and last night we pulled an end tank off. More than half of the chanels were blocked. So now i'm going to get a second hand car from a mate tomorrow (good timing) and hopefully its radiator is in better condition than mine, otherwise i'm off to pick a part.

Thanks for everyone's input about different sensors, guess i better start considering the main culprits before the bigger picture.

Cheers

Bennie

steptoe · Post by **steptoe** » Thu Oct 18, 2007 12:05 am

and send that radiator through the shop before you shove it in unless you find a newie at the wreckers

YouTube · Post by **El_Freddo** » Fri Oct 19, 2007 12:08 pm

steptoe wrote:and send that radiator through the shop before you shove it in unless you find a newie at the wreckers

Its in now at the radiator place, dropped it off about half an hour ago. The guy broke the tank pipe that takes in all the hot water. It was an orangey colour - apparently this means that its taken some heat and has been weakened. Lucky i took in my current radiator, he's going to use that tank on this "new" core and while he's at it the cores will get a flush and scrape out while he's there. I'll be picking it up this arvo...

$100 same day service, not bad i don't think considering I need the car this weekend...

Cheers

Bennie

steptoe · Post by **steptoe** » Sat Oct 20, 2007 12:04 pm

think i have another sworn convert here....

YouTube · Post by **El_Freddo** » Sun Oct 21, 2007 8:08 pm

Well it was defenately the radiator. All up it cost me $20 cos it apparently wouldn't seal on the end tanks properly... That included a bottle of stop leak.

Bascially my "new" radiator is just as stuffed as the last one but the cores have been cleaned. All the fins have fallen subject to corrosion.

Even so, it held up in near 30 degree heat at all speeds including working hard in 4wd.

I'm now looking into an MY dual core brass radiator and shoe-horning that in, its only 6mm taller...

Cheers

Bennie