Pontiac Owners Club UK

Hi all, i gave the car its first run out last night, all was well except the temperature. Im fairly confident my gauge is right as it was spot on in the 5.0 engine, its a digital aftermarket one, It used to sit at about 170 driving around, then in traffic it would creep up and id switch the fans on and watch it come back down....no problems

Last night on the move it kept going up and levelled off about 200 even when i was doing about 60 down the dual carriage way, then i hit traffic, turned the fans on and it wasn't really bringing the temp down, it just sort of hovered at 220, at one point it nearly got to 240 so i pulled over thinking it would be boiling over but the coolant in the tank was fine, it was a little bit past the hot mark on the bottle but it wasnt bubbling over or anything, there was no smell of burning coolant or mega heat when i opened the bonnet either. All the hoses were hot, the rad was hot so that means the thermostat is working

Got the same air damn, i replaced the black plastic rad cover with a sort of chicken wire mesh grille as it was all warped and snapped.

Last night someone said i might have the wrong water pump. My mate gave me it brand new, he ordered it for his 83 then blew his engine. I thought it was the right one for an 87 with it being non serpentine ? apparantley they changed the flow of the cooling system one year.

Ive just ordered a laser temp gun so i can physically check the temp of the block and take it from there. Im just not 100% sure about this water pump, one person is saying its probably the wrong one, and another is saying it will be the right one

Make sure where you measure with the IR gun is black or as close to black as possible as they don't work well on silvers whites or light colours.

Do you have a rad cap where you can vent it with a lever???

also, did you exchange the radiator for a larger one?

No the part numbers between the 5.0 and 5.7 rads all came back the same ?

i bought my new rad when i still had the 5.0 then checked when i got the 5.7 and they should be the same

I fixed my transmission fluid leak tonight, ran the car up, the temp climbed slowly and steadily just sitting in the garage.

so i thought id take it for a drive, i was out for about 20 minutes and all was fine. The gauge was still reading hotter than what im used too, it was going between 85-90 degrees C (around 190 degrees F) and this was constantly on the move.

I put the car back in the garage and just let it run and it started getting hotter obviously, i switched the fans on when it got to 100 degrees C on the gauge (212 degrees F) and it came back down to about 200 according to the gauge, but wouldnt go any cooler.

I opened the bonnet and again everything seemed fine, the coolant was on the HOT mark on the bottle, the engine didnt feel overly hot, all hoses were hot, the top rad hose felt a bit squidgey, so the thermostat must be open if waters going all the way around the system.

I turned my heater on too and i get nice hot air through that.

Sooooo, back to my original question i guess, does this seem normal for a 5.7 ? im just used to the car running 20 degrees cooler when i had the 5.0

Im still waiting for the IR gun to get delivered so i can compare

with fans turned on manually then mine stays about a third of the way up
will look on sunday to see what that is in degrres

Cheers John

My temp gun turned up today so i thought id give it a try. I got a few different readings depending on where i pointed the gun. But basically the car ran for just over 20 minutes, idiling in the garage, i turned the fans on and off according to the temp so it didnt get too hot and it did cool down. The reading from the gun changed depending on where i pointed it, but on the intake and top hose is where it was around the same. Pointing it at the sender for the gauge didnt work as i think the heat from the headers was bumping the temperature up quite a bit









These were taken with the car running after the fans had been on. So maybe this is just what the car is going to be like then, its definatley not overheating, the coolant was bang on the HOT mark on the bottle again

Am i just being paranoid and this is how a 5.7 should be ?

is the ignition timing over advanced? 235 f seems very hot.

I think that reading is the thermostat housing itself holding heat.

the timing is set at 8 degrees, i might try it back at 6

i had it out on Sunday and it seemed fine, fairly cool driving around, warmed up when instopped outside the house while i opened up but i put the fans on and it was holding the temp at about 200

Gave the car its first proper run out today, an 80 mile round trip ! the cars runs great, stayed nice and cool all the way to the event down the motorway, and the temp steadily rised when i slowed down onto normal roads as it does.

It ran fine all the way back too but the temp crept up when i was 5 mins from home on the slower roads and traffic lights etc, i had the fans running but it just wasnt bringing the temp back down enough again.

When i got home i popped the bonnet and it wasnt bubbling over but i could hear coolant moving or gurging so it might of been close to overheating. I had this problem years ago on the way back from KnightCon, cool as anything on the motorway but when i pulled off the temp went really high even with the fans running, back then i cured it by draining the coolant and flushing through with a hose pipe, but surely thats not the problem now as its all new coolant, water pump, radiator etc

Im wondering if i need a bigger air damn or something if its not getting enough air when going at slow speeds ? but saying that surely the twin fans should bring the temp down anyway, hmmmm

You could try changing the 160° to a 180° thermostat. Maybe with the 160, the coolant isn't staying in the rad long enough.

Could do, i dont know if that would add to the heating up when going slow after driving on the motorway or not ?

at 180 degrees (190) both would be open fully so would not have any effect when overheating occurs
is it the correct rad for the car? only time I had same thing was with a six cyl. rad fitted to a V8
are the fan shrouds close to rad?
with twin fans going it should stay close to 1/4 on gauge

thats what i thought about the thermostat too, it doesnt cool down that much when running for the thermostat to close again anyway ?

Its a stock replacement rad, exactly the same as the one i had with the 5.0 engine, ive checked the part numbers and they are the same for the 5.0 and 5.7 engine, i also checked the water pump but its ok, it was bought for an 83 but works with my 87 as its pre-serpentine so spins clockwise.

The fans i simply unbolted off my old rad and bolted to my new one, they worked great with my old engine, to be honest i rarely had to turn them on unless i was stuck in traffic and they would bring the temp down nicely.

all looks good

yup, air dam is still there, ive always had the shorter version but the 5.0 stayed cool as a cucumber even just cruising around at slow speeds so it cant be that. ive added a mesh grille to the radiator support, but its like chicken wire so i cant imagine it restricting any air at all causing it to heat up



the stock one which is a black plastic thing was all warped and cracked so i took that off and put that on instead

that would not affect it (aircon fitted cars have a heat exchanger in front of the rad that stops more air than that mesh)

yeah i remember binning that little radiator years ago when i removed all the air con

Just started it with rad cap off, someone said i should see the coolant being sucked down into the rad a bit? but it sort of swirled round then started rising so i switched off otherwise it would if started dribbling out

is that right or wrong for an 87, non serpentine so i think its a clockwise system ?

should go down a bit when revved
are you sure there are no air locks

well i was watching the coolant with it idiling and there were bubbles, but i dont know if they were just caused by the coolant moving, they seemed to settle as the coolant started rising, but then i had to switch the engine off otherwise it would of started dribbling out. I didnt rev the engine with the cap off, i might try that again tomorrow when im in the garage.

Still got air in the system causing it to heat up ?

that or headgasket

Its got brand new head gaskets ! Better not be that

Put the 180 stat in, cant really say its any different, pulled it in the garage after driving it for 30 mins and left the fans running and it was holding the temp at 230 :/

stays pretty cool driving but when you slow down, ir start stop, same again

i ran it for a while with the cap off the expansion tank until the bubbles stopped so i assume its bled