SalzundPfeffer

Trying to troubleshoot why my car is running a little hotter than normal after I did some work on the front end. Sorry for the length of the post...just want to be detailed.

Year:
1984

Items replaced:
Water pump – new from Allzim – PN 951.106.021.10
Thermostat – new from Pelican – PN 944.106.019.00.M2
Thermostat seal – new from Pelican – PN 944.106.929.08.M2
Thermostat washer – new from Pelican – PN 900.234.160.00.M100
Fan switch (92C) – new from Pelican – PN 823.959.481.F.92.M2
Radiator cap – new from Pelican – 928.106.257.03.M148
Flushed out radiator with some Prestone cleaner and garden hose prior to reassembly.

I used Clarks information regarding these components as a guide.

Symptoms:
-Car consistently runs with the temp gauge at the 3/4 dash mark (corresponds to ~97C per Clarks reference - http://www.clarks-garage.com/pdf-manual/elect-19.pdf).
-With old components, car would run at ~1/2 dash mark. So, it’s running a little warmer than usual.
-Upper radiator hose is warm/hot but not very firm after my ~20min commute on the interstate.
-Lower radiator hose is cool to the touch. Ambient temps ~30-35F.
-Radiator hot to the touch. Outlet by the lower radiator hose is cold. Still need to do a better inspection and see how much of and where the radiator is hot.
-Reservoir is cold as well.
-Had some coolant coming out of the overflow last night too after I turned the car off.

Other items to note:
-It seems like the groove on the “new pump” is the same place as my original pump. I could not get the t-stat, new seal, spacer and snap ring in the new pump. There wasn’t enough room for the snap ring to grab behind the lip of the groove. So, I ended up leaving the spacer out because it would not fit. Even with the new thicker seal for the t-stat I had a hard time getting the snap ring to seat in the groove. Is this something unique to the pumps that Allzim has? Is the spacer required with the new thicker seal?

-I put new belts and rollers on when I did the pump and tensioned using Arnworx tools.

-At start up there has been some whirring/whining noise until the car gets warmed up. I am just assuming this will subside over time as the belts stretch. Plus it has been cold here 20-30F. I’m not sure if this is the pump or rollers or both. Bottom line, everything is whisper quiet after my 20min commute.

-The radiator fan had been running more often than usual, but now it’s colder out and I haven’t noticed it run. So, I think the fan switch is working. I’m just worried about summer driver next year, it’s going to be running constantly if I can’t get any flow through the radiator.

My thoughts:
-I’m suspicious of the problem I had with the t-stat installation and the location of the groove on my new pump. The way I installed it is there anyway the flow could be choked down?

-The whirring noise at startup. Could this mean that the pump is bad? It goes away after warm-up so I think it’s pumping. Plus, the upper radiator hose and radiator are hot and I’m getting heat in the cabin, so I think it’s pumping.

-I did some reading on the forums about clogged radiators. I did a forward and reverse flush with a garden hose and prestone cleaner. It appeared that the radiator wasn’t clogged when I was hosing it out. What are the chances this is clogged up?

-What about air locks? Do I just need to do a better job venting the system?

I think my first step will be to pull the t-stat and leave it out and then drive it for another week to see if symptoms persist. Will this hurt the car? I assume I just won’t have heat while the t-stat is out. Just wanted to get everyone else’s opinions on things to check.

Thanks,
-bp

turbodave

"What about air locks? Do I just need to do a better job venting the system?"

Before removing and running without the thermostat try elevating the front of the car as high as practical (min.6") and rebleed the coolant sys. with the heater in the max. heat position. The problem with running without the thermostat in cold weather is the obvious, plus the oil uses water temp. to come up to operating temp. via the oil/water heat exchanger. There are a couple of places in the head that can trap air in the sys. so the higher you can raise the front of the engine the better.

StoogeMoe

It sounds to me like the classic air bubble problem. You need to bleed the system properly to get all the air out.

The clue is the lower radiator hose temperature. That indicates that the water is NOT flowing through the radiator. This could also be caused by the flushing, which dislodged a bunch of crud and clogged it up. But trying bleeding the coolant first with the heater valve fully open.

SalzundPfeffer

Thanks for the replies.

1. Can I rent any equipment at an auto parts store to help facilitate the bleeding of the system better?

2. If I have a clog, can I do anything about it while the radiator is in the car? Radiator flush, chemicals, etc.

Thanks,
-bp

86 951 Driver

Get a coolant pressure tester. You can bleed it while it is cold. Then let it get to temp then bleed it again the normal way.

V2Rocket

I had a customer recently who, among other things, had issues with running hot. His 1987 944S would run at the 3/4 mark consistently. I put in new WP/belts/radiator/low temp thermostat/fan switch. Also replaced his OEM AC condenser (full of birds and rocks) with a new aftermarket one. Now the car doesn't even get to the halfway mark, and the AC is ice cold.

Your radiator, depending on age, might have some scale buildup inside it. That crud is a very strong thermal insulator. The water passages on the radiator core are very small and could clog up easily. Try bleeding the system of air, but if the problem persists you may need to replace the radiator.

Jack the car up with the front end in the air and crack the bleeder screw, and let the car idle until it gets warm, give it some throttle and open the heater valve etc to get all the coolant circulating. When you throttle up and get water coming out of the screw consistently then you're probably good to go. Add water to the expansion tank if needed.

divil

Yes most of the Advance/Autozone type places lend coolant system pressure testers. They come with range of adapters for different expansion tanks and a hand pump with a pressure gauge.

With the engine cold, remove the bleed screw fully, and use the pump to pressurize the system from the expansion tank, until coolant flows out of the bleed opening. Once you have a smooth stream of coolant coming out, put the bleed screw back in and then fire up the engine and follow the normal bleed procedure (i.e. get engine hot, crack bleed screw until air stops coming out, re-tighten bleed screw, repeat)

BTW, any time you're filing the coolant system, remove the bleed screw completely first (don't just crack it).

SalzundPfeffer

I did some more diagnostics last night after my 20min commute home. Left the car on and used my IR thermometer to check temps around the engine. Heat was on too.

First off, cracked open bleed screw and I had quite a bit of steam/air rush out. Then after that, the hose was empty. I would squeeze it and nothing came out of the bleed screw, suggesting I have a lot of air in the system.

Anyway I let the engine continue to idle and kept an eye on the temp gauge. Aimed the thermometer at the pump housing. Right around 80C I would start to see some dribbles coming out of the bleed screw, suggesting the T-stat is opening when it should. However, almost immediately when the T-stat would open, the radiator fans would kick on. So, the first flow of fluid out of the engine to the radiator must be over the 90/92C threshold to trip the thermo-switch.

The fans would run for a minute or two and then shutoff. Ambient temp was around 30F last night. Seems fairly normal.

The temp gauge seems to read somewhat high. When my gauge was indicating 97C, I was measuring the area around the temp sensor at ~92C. Occasionally I would get a reading on my thermometer around 100C just before the t-stat would open and run coolant through the radiator.

My conclusion from this diagnostic was that the flow rate through the radiator is on the order of a trickle based on what I was seeing come out of the bleed screw when the t-stat opened and the amount of air remaining in the hose. It’s like the pump doesn’t have enough fluid to work with. But, you would think regardless of how much fluid is in the system, every time the t-stat opens it would fill the radiator with what is available in the block. No?

I’m going to use a pressure tester from an auto parts store tonight to make sure I get the radiator and upper hose, along with the block, completely full of coolant. I’m thinking my flow rate is down and that is causing the high than normal temps. Plus, I think the thermal shock of the fluid just coming out of the upper radiator hose when the t-stat opens is what is causing the fans to kick on right away.

Jfrahm

You can affect the same pressure bleed by blowing into the overflow tube with your hand over the water neck. Open bleeder, blow, close bleeder, inhale, repeat. Easy. Clean the overflow hose and do not swallow any coolant. Once you are done get the engine nice and hot and the heat on full and give it one burp with the engine running, parked nose up on a nice steep hill.

turbodave

"I’m going to use a pressure tester from an auto parts store tonight to make sure I get the radiator and upper hose, along with the block, completely full of coolant"

Careful with how much pressure you apply. The end caps on these radiators are plastic. I don't know how much it would take to crack one, but then again I've never known anyone who ever needed a pressure tester to bleed the coolant sys. on a 944. Best of luck..Dave

divil

You'll be ok if you're using it to bleed the system...you won't really be putting any real pressure in there, unless it's somehow blocked. You're just pumping enough to make the coolant push the air out.

SalzundPfeffer

I'm fairly sure I have all the air out of the system. I'm starting to wonder if my temp gauge reading is off. I just replaced the sending unit so I'm fairly confident that is not the problem. Couple of questions.

1. Where is the ground for the temp gauge sender. Some threads say it's on the back of the bell housing. Where exactly? Is it hard to access?

2. As I was letting the car idle last night at about 35 degrees ambient the radiator fans would kick on periodically for about a minute and then off for about five. Does this seem typical for idle? It seems like when the t- stat opens the first rush of fluid into the radiator is enough to trip the thermoswitch. I never notice the fans run while I'm in motion.

Jfrahm

What temp thermostat did you install?

Can you measure the temp of the hoses? Meat thermometer? IR thermometer?

PDX-944

its safe to assume that in replacing the water pump you replaced or at least removed the belts?
the belts will whine if they are too tight. i replaced mine last week and i get a whine now as well. my bsb is a little tight i think.
did you drill the 1/8" hole in the thermostat? the first thing to do is park it with nose up or jack up the nose, and pop the coolant bleeder, then fill up the tank. it will get full, but slowlyyyy go down, then fill up more, and it will slowlyyyy go down again until coolant comes out the bleeder. may take a bit. but thats all i did, with the hole in the t-stat also. and mines been running much cooler with the lower temp t-stat i put in. still gets 3/4 though when parked/idling for a while. at least now i can drive without the fan blowing hot air =p