mpeters951

Guys - thanks so much to all here.

Here's where I am:

Idled for a good 20 minutes in 85f weather conditions. Gauge is reading a high of 5/8's and low of 3/8's when up to normal oil temp. Decent relatively constant flow of coolant from bleeder. Heater blasting out hot. No gurgling from core. No leaks anywhere.

The weird open questions are:

How can the lower rad hose possibly be cool after car fully up to temp - that should be loaded with hot water as the t'stat opens at 160f ?

Gauge occasionally "bounces" from say, 3/8's to 1/2 almost as if you hit it sharply with a mallet. Gauge has bounced up and bounced down like this.

Switching on/off the heater bounces the gauge approx 1/2 step gauge marks


MP

chrenan

Bouncing needle is the air in the system (hotter than the coolant) passing by the temp sensor. Get the nose of the car sky high and bleed, bleed, bleed.

JohnKoaWood

Questions... do you turn the heat on full blast when you are bleeding?

if not you are trapping the air, not bleeding it out

Have you replaced the sensor itself?

My 951 had a badish sensor..replaced sensor and readings went back to normal

How much coolant / water are you using from empty to full?

should be roughly 1.9 gallons... I use 1 gallon Porsche antifreeze and 1 gallon of distilled water and have NEVER had a problem with my temps...

mpeters951

After leaving this pig generally alone for a couple weeks, I ran it at idle for 30 minutes w/ heat on and front of car elevated 12".

Intermittent steam and stream from bleeder. Gauge action was pegged at 3/4's (207f) and would drop to just a hair over half when revved to ~ 2500 rpm. Increased rev's would get a pretty quick drop in gauge temp.

For me the confusing reality is the bloody lower rad is cool as can be, like ambient temp while gauge is showing a good deal more temp than the point at which the thermostat opens. In this case 160f, tested and verified.

Can someone chime in on failure modes of the water pump. Peanut suggests above that the impeller may not be moving water; I'm wondering if that's the issue here. Radiator has been flushed and is clean, block flushed and clean. All hoses are clean and not collapsing under load.

No mixing of coolant/oil whatsoever. No leakage at the water pump behind the belt cover. IS there any way to determine if the water pump is actually moving water ?

Anyone ?

krystar

u should be able to see water movement in the expansion tank. especially if it's not filled completely.

very wierd...

StoogeMoe

Just an interesting thing that happened to me. I bought a new thermostat. It even tested fine in a pot of hot water on the stove. Put it in the water pump and it didn't work. The car ran hot. I got another "new" one, put it in, and everything has been fine for years.

The lesson is - Sometimes a new part can be bad.

With the lower rad hose cool, you're obviously not circulating water. But it could be you still have an air pocket. That would explain the steam. Did you try the mouth to mouth method on the expansion tank? It has never failed for me.

peanut

yeah i'd go along with mo on the thermostat

If i were you I'd make sure that the thermostat is the right temperature setting and not a European setting.
Colder climates like Europe require a thermostat that opens at a higher temperature to maintain adequate coolant temperature so the engine runs efficiently.
You may have a Euro stat fitted.

Incidentally you never answered my Q about the electric fans ? Do you have them connected ? and are they cutting in when the temperature rises ? no stationary engine is going to cope without fans running at this time of the year.

ZW 944

CHECK YOUR THERMOSTAT OUTSIDE THE CAR.

I went through THREE new thermostats trying to solve my problem.

First the car was overheating after I replaced the thermostat when doing my Head Gasket job.

Replaced it with another new one from napa

ran hot right after replacement, bought new OEM thermostat for OEM temp, installed.

Still runs too hot. no improvement. take thermostat out, test it and the other two against each other in a boiling pot of water with a good thermostat, none of them opened when they were supposed to.

Bought Low temp thermostat from 944online, checked in boiling water, opens when normal thermostat is supposed to. Install on car, no problems since.

CPR

Are 100% sure the T-Stat is installed correctly (flow)?

thirdgenbird

ive seen some of this with my 87 924s as well

peanut

+1

marky522

First thing i would be doing is verifying a good bleed, i am a firm believer in vacuum filling these cars, I can fill the cooltant in less than 5 minutes, flat on the ground and the tool is less than $100.

Second, I would also be looking at the waterpump impeller, if its really is cooling down that quick when you rev it, it could very well be slipping, but it can only slip so much so when you rev it, coolant starts moving.

Third, gauge... I would get an IR gun and check your block temps before and after the thermostat, this could simply be a faulty gauge, ground, or cluster, any resistance added to the circuit will affect the reading.

Fourth... I wouldnt rule out a HG, just because your coolant is clean, no oil doenst mean you dont have a leak, allowing air/fuel into the cooling system only while running, you can get test strips to see if you have combustion byproducts in your coolant, and with as much as you have flushed your system you really shouldnt have much.


I disagree with this comment, a coolant temp sensor cannot read when it is covered in an air/steam pocket. air/steam doesnt conduct heat like water/coolant

Mark

mpeters951

Thanks all. I've got this running well and behaving much cooler. And yes, t'sat installed correctly. That is 160f new unit verified on the stove. Fan switch is higher temp - and yes - I will match that to t'stat soon enough. I'll also validate the ground.

But here we are:

Fans cut in normally and operate normally. What I'd done as the latest step, that being to grab the auto parts store pressure tester, is to put ~ 15psi into the system which immediately exposed my brain fade in not having tightened down the water pump side of the lower rad hose enough. Coolant was pissing out there under pressure big time.

Cured that clamping issue, "pressure bled" the system, and viola - hugely steadier and lower temps in all idling and running conditions. Seems as though, w/o a fully "pressure-izable" system (owing to my formerly loose rad-hose to wp connection) the lower hose was never going to become full of hot coolant on it's way to the radiator. That was confusing the hell out of me.

I may burp & bleed a bit more, but it seems things are nearly back to normal state.

Thanks all for help and counsel - all comments have been appreciated here.

Mark