H2

In my Chevy days, bad timing could cause overheating.

Is it possible that in the process of replacing a T-belt or cam gear that the timing could get off a bit, causing a 928 to run warmer than it needs to?

Just curious. I've never seen anything posted about this.

H2

Mrmerlin

since the timing is controlled by the puter the cams would have to be way off for this to happen and the car wouldnt run well.
On a chevy the timing effects the whole motor, on a 928 the cams would both have to be way off

tailpipe

on my friends 86 the timing belt jumped a couple teeth not enough to damage the motor but just enough to send raw fuel down into the catalitic converter which then tried to burn it off like it should which then caused the converter to glow red hot which then set fire to the sound deadner on the fire wall which then burned most of the wires and hoses on the back of the motor good thing it was the day after his mechanic changed the timing belt the shop covered the cost to repair/replace everything didn't hurt the paint or anything inside the dash was just really lucky he had a fire extinguisher with him in the car and got the fire out fast just goes to show you should always have a fire extinguisher in your car at all times it might not be you that needs it it might be someone else driving close by

H2

Wow, that qualifies for overheating! It proves that things could be worse. And that, normally, cam timing really doesn't affect engine overheating that much as compared to the Chevy/Ford, etc.

Thanks,
H2

H2

John Speake

Hi H2
One common reason for overheating on old engines was if the ignition was rearded. And as the distributor and coil points (or electronic pickup) for spark timing was commonly taken off the camshaft then a mistimed cam could cuase overheating.

This isn't possible with the 928 because ignition timing is determined by the flywheel speed sensor, totally independant of cam timing.

Is your 928 overheating after a TB job, or is this a hyperthetical question ?

hacker-pschorr

Oh sure, easy for you to say about the EZF / EZK cars.....

heinrich

H2 your car isn't overheating apparently ... but if it is, I look at the water pump as number one offender and the thermostat as number 2. After that, temp sensors ....

soontobered84

My vote for the most common overheating reason would be the lack of coolant flow through the radiator due to residue and crap left from tap water use in the system.

H2

Yes, Henrich. Overheating is why I didn't attend the Track Attack in Spokane today.

On twisties, pushing it hard, uphill, it will boil over if you don't catch it quick. And on turning around and practically coasting down hill it doesn't cool as fast as it should. Reallll Sllloooow cooldown.

I've tried about everything but suspect it's something simple (or REALLY complicated!)

New thermostadt (3rd one. first two were 100 degree, this latest is 150..we'll seed if that makes a diff and hope it doesn't damage my brandnew radiator.

Send new thermostadt carefully installed, right orientation, inside gasket correct, nothing tilted. Checked thermo on boiling pan of water...functions fine. Also measured inside thermo distance to the seal behind the thermostadt. Seems to be correct.

New, well seated seal behind the thermostadt

Brand new radiator (Devek style, only 1/4" thicker)

Block flushed and reverse flushed..cleased with tide....clean a whistle. No sign of any kind of build up.

New Dex Cool mixed 50/50 and one bottle of water wetter

Both fans work on cue

To make sure the new Water Pump was working, I spliced in a piece of clear hose on the hose coming out of the front passenger's side....No circulation until it gets warm, then the 83 degree thermostadt obviously opens up and the WP pumps a heck of a lot of water through the system. WP has to be OK, it's new too and certainly functioning as you can see the coolant really pumping through the system.

I see no bubbles in the coolant but have ordered kit for testing exhaust signs in coolant to see if there might be a head gasket issue. Just to eliminate this.

No coolant leaks at all. Or coolant loss. No obstructions in hoses. When flushing engine water also flows well out of all orifices including two engine drain plugs.

Burped well...no air pockets.

All new temp gauges.

What did I miss?

Actually, it seems like the thermo may not be opening wide enough to let enough coolant through but I've quadrupled checked that area and all's within spec. The temp gauge rises to the top white line and then when the thermostadt opens the needle drops to below the line. It's working right...but it's just not running as cool as I would like. I know some 928s run with the needle towards the top but the car shouldn't boil over every time I run it hard.

I checked the AC radiator that's in front of the new radiator. I'm not running AC...and the fins are not plugged up with anything.

What have I missed? Obstruction inside the block or heads? I can't see inside the block but water flows great through a hose. It has me stumped.

Thank you all.

H2

H2

Here's the rig I set up to check water pump flow. When thermostadt opens, a lot of water gets pumped through the hose.

ALSO, I plugged an old thermostadt open with a wired-in bolt and the engine ran cooler. This makes me think it may be the thermostadt but ithe one in there is obviously functioning...but is it' opening up enough? The rubber gasket inside is great shape and seated well. It's a new Porsche (Wahl) thermostadt, 83 degree. I keep thinking the problem has to be water flow...but it's all checking out...I am tempted to drill a couple of holes in the the end where I have the bolt wired. Note: the thermostadt shown is for testing only, although I'm temped to use it since the engine seems to run cooler with it.

H2

ZEUS+

When cold, coolant circulates throught the block. When warmed up and tstat opens it closes the passage for warm up circulation and coolant now flows through the rad to be cooled. Coolant needs the proper mixture so it can expand into the water. Have you checked the temp difference on inlet and return of rad ? You should have the inspection hose on the inlet side.

Daniel Dudley

How hard would it be to check ?

You have a curious problem here. Has this car always overheated for you ?

tailpipe

try hitting the performance shop they have a product up here called water wetter that improves the cooling ability of the coolant might be an easy cheap fix just pour it in

H2

This car has always had this problem since I bought it.

Water wetter does't make much difference.

It's getting better though.

On the '85S I had, the temp never rose above the first bar, except in 100 degree weather and really slow traffic.

When idling in driveway, it' will heat up to more or less 195 degrees. It's only in spirited, hard driving that it overheats.

H2