Murphy's Law catches up
02-07-2008, 04:10 PM
#31
Race Car
Wait, before you jump in there again, let me see if I understand this correctly. You have lost some coolant and now the engine overheats and there is no hot air out of the heater? Did you properly burp the system after adding back the coolant? I'm not sure what bleeder hoses you are talking about? Does a '78 have something else there than an '86? On my car I have to spend days burping and topping up until the system is free of air bubbles. If I don't do it, I will have no hot air out of the heater and coolant circulation at low RPMs is not enough and will overheat the car. I remember I would have to hold the RPMs at over 2,5k and then hot air would start coming from the vents and the temp gauge would make a huge drop.
Park the car on as steep an incline as you can, nose pointing upwards. Remove the coolant cap (carefully if the car is warmed up) and start squeezing the upper radiator hose. Start the car, put the heater to max heat and continue the hose squeezing. Top up coolant if it goes down. Replace coolant cap, go for a spirited drive and repeat.
Of course, this will only work if you no longer have any coolant leaks...
Dan
'86 928S 5-spd w/LSD
Park the car on as steep an incline as you can, nose pointing upwards. Remove the coolant cap (carefully if the car is warmed up) and start squeezing the upper radiator hose. Start the car, put the heater to max heat and continue the hose squeezing. Top up coolant if it goes down. Replace coolant cap, go for a spirited drive and repeat.
Of course, this will only work if you no longer have any coolant leaks...
Dan
'86 928S 5-spd w/LSD
02-07-2008, 04:19 PM
#32
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Hi - I don't think there is still air in the system. As part of diagnosing this I have the coolant expansion tank remotely connected via a 3 foot hose - it's way above anything else in the system now (on top of the spider - and no the bleeder and main lines aren't crimped) - and the level in the tank doesn't drop when the car is running and the hoses are squeezed. The level does go up if the engine is hot and I vent some pressure out of the cap. I've also been running the engine up to about 3k as it warms to try and chase out any last bits of air. Still no heat from the heater.
02-07-2008, 06:14 PM
#33
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First, you say you have put over 1,000 miles on the car since the belt replacement. Check the belt tension to be sure it's able to turn the water pump. Do you know if the belt warning system is hooked up and working? The tension is VERY important.
Second, the thermostat sets the minimum temp of the engine after warm-up. Once open; heat transfers to the radiator, subject to water and airflow. If flow is inadequate and the thermostat is fully open, the problem is the water pump, or radiator restrictions. Check radiator first, they’re more common, easier and cheaper to fix. Airflow also varies, at high temp, at idle, the fans provide airflow. That setting comes from the thermostatic clutch on the belt-drive fan and from the temp switch and AC operation for the electric fan on pre S4’s.
This all interacts so a car that overheats at low speeds but is OK at high speed often has airflow problems. Due to a fan clutch, electric fan, or thermo switch, or both. A car that overheats at high speed often has water flow problems, usually a restricted radiator. A car that overheats right after startup has water problems, a thermostat stuck shut, an inop water pump, a plugged radiator, or no coolant.
Lower temp thermostats let the engine run cooler, if there’s radiator capacity. If your car overheats, a thermostat only helps if it was stuck or plugged and is restricting coolant flow. When the thermostat opens, it expands backwards, against a gasket (P/N 928.106.163.00) behind the thermostat, closing the passage and forcing the water through the radiator. The gasket deteriorates and the thermostat can’t completely close the passage, so some of the coolant recycles through the engine, getting even hotter. A low-temp thermostat doesn't flow more; it flows sooner. Fan operation must be coordinated with the thermostat to stay cool. Match the thermostat temp to the fan switch, so the fan doesn't run before the thermostat opens.
In slow traffic with just fan air and low water flow, it's normal to see the temp come up a little with AC. But, up towards the red area isn’t normal. Flush the debris out that gets packed in the condenser and radiator, blocking airflow, with a hose from the front, but don’t bend the fins.
Redline Water Wetter made it almost 3 needle widths cooler. I've had good results running the Prestone cooling system cleaner through the engine. Follow the directions about removing all the old coolant first. Drain and flush the cleaner and water mixture out of the engine, remember to pull the block plugs to get all the sand, rocks and other debris out of the water galleys. Install new seal washers and anti-seize on the block plugs. Torque to 25 ft/lbs., be careful not to strip the block. Use just enough Dex-Cool for the freeze protection needed, use distilled water to reduce mineral scaling.
I have never found the burping process very effective in getting the air out of the system. Air pockets are common after a cooling system service. I’ve released large belches of air after filling the overflow tank, then running up to operating temp with the system open. The gauge read cool because it was reading and pumping air, yet the level looked OK. Remove the water temp sensor located in the cooling crossover manifold at the front of the engine. Fill the system from here and reinstall the sensor. Remove the radiator end of the vent hose until you get a small stream. This is the highest point in the coolant system, and will get rid of the air bubble. Start the car and watch the level.
Second, the thermostat sets the minimum temp of the engine after warm-up. Once open; heat transfers to the radiator, subject to water and airflow. If flow is inadequate and the thermostat is fully open, the problem is the water pump, or radiator restrictions. Check radiator first, they’re more common, easier and cheaper to fix. Airflow also varies, at high temp, at idle, the fans provide airflow. That setting comes from the thermostatic clutch on the belt-drive fan and from the temp switch and AC operation for the electric fan on pre S4’s.
This all interacts so a car that overheats at low speeds but is OK at high speed often has airflow problems. Due to a fan clutch, electric fan, or thermo switch, or both. A car that overheats at high speed often has water flow problems, usually a restricted radiator. A car that overheats right after startup has water problems, a thermostat stuck shut, an inop water pump, a plugged radiator, or no coolant.
Lower temp thermostats let the engine run cooler, if there’s radiator capacity. If your car overheats, a thermostat only helps if it was stuck or plugged and is restricting coolant flow. When the thermostat opens, it expands backwards, against a gasket (P/N 928.106.163.00) behind the thermostat, closing the passage and forcing the water through the radiator. The gasket deteriorates and the thermostat can’t completely close the passage, so some of the coolant recycles through the engine, getting even hotter. A low-temp thermostat doesn't flow more; it flows sooner. Fan operation must be coordinated with the thermostat to stay cool. Match the thermostat temp to the fan switch, so the fan doesn't run before the thermostat opens.
In slow traffic with just fan air and low water flow, it's normal to see the temp come up a little with AC. But, up towards the red area isn’t normal. Flush the debris out that gets packed in the condenser and radiator, blocking airflow, with a hose from the front, but don’t bend the fins.
Redline Water Wetter made it almost 3 needle widths cooler. I've had good results running the Prestone cooling system cleaner through the engine. Follow the directions about removing all the old coolant first. Drain and flush the cleaner and water mixture out of the engine, remember to pull the block plugs to get all the sand, rocks and other debris out of the water galleys. Install new seal washers and anti-seize on the block plugs. Torque to 25 ft/lbs., be careful not to strip the block. Use just enough Dex-Cool for the freeze protection needed, use distilled water to reduce mineral scaling.
I have never found the burping process very effective in getting the air out of the system. Air pockets are common after a cooling system service. I’ve released large belches of air after filling the overflow tank, then running up to operating temp with the system open. The gauge read cool because it was reading and pumping air, yet the level looked OK. Remove the water temp sensor located in the cooling crossover manifold at the front of the engine. Fill the system from here and reinstall the sensor. Remove the radiator end of the vent hose until you get a small stream. This is the highest point in the coolant system, and will get rid of the air bubble. Start the car and watch the level.
02-07-2008, 06:31 PM
#35
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When the thermostat opens, it expands backwards, against a gasket (P/N 928.106.163.00) behind the thermostat, closing the passage and forcing the water through the radiator.
I keep hearing about this secondary gasket - where exactly is it in this diagram (not trying to be a smartass, I really have no idea what everyone is talking about).
02-07-2008, 06:35 PM
#36
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The rear seal is not shown in that diagram - its too early a pic. It goes in 83-> models, in the hole half obscured inside under the thermostat, directly under item 6.
jp 83 Euro S AT 51k
jp 83 Euro S AT 51k
02-07-2008, 08:51 PM
#38
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The upper radiator hose connects to the cross over. If you were to pull it and replace it with clear hose, and the t-stat would be stuck or closed (cold) water is coming out of the heads and going down to the pump to be pushed through the engine. water is being pushed out by the heads by the pump. This water will not flow to the upper radiator, as the radiator is , in effect, clogged, until the t-stat opens. (blocked) all the water goes to the cross over, and the lower pressure area at the inlet of the pump when the t-stat isclosed (cold) if it were hot, or pegged open, it would be a fine test, as it would be pushed out via the heads with a source of fluid coming from the lower radiator hose. so, no flow, no pump working. However, if you dont have the t-stat plugged open and you just wait for the engine to heat up, there would be no flow out the upper radiator hose, because, where is the water to go, it cant exit the bottom of the radiator and go into the engine, as that path is blocked!
It just seems so simple to just peg the T-stat and disconnect the feed line (lower radiator hose) and if water is pumped out, its working. if it doesnt move, pump is bad.
One time , before i figured this out, i put the clear plastic hose between the upper radiator hose at the exit bridge and the lower raditor inlet. (at the t-stat) . the problem is here , is that you have to wait 5 -10 min for the engine to heat up to see flow, and if you never do, you wll never know if it is the pump or t-stat. so, thats when i came up with pegging the t-stat open and feeding the water to the engine with a garden hose. also a good way to flush with distilled water. run a couple of gallons through the system , then just drain the radiator. fill with distilled and you are good to go.
mk
It just seems so simple to just peg the T-stat and disconnect the feed line (lower radiator hose) and if water is pumped out, its working. if it doesnt move, pump is bad.
One time , before i figured this out, i put the clear plastic hose between the upper radiator hose at the exit bridge and the lower raditor inlet. (at the t-stat) . the problem is here , is that you have to wait 5 -10 min for the engine to heat up to see flow, and if you never do, you wll never know if it is the pump or t-stat. so, thats when i came up with pegging the t-stat open and feeding the water to the engine with a garden hose. also a good way to flush with distilled water. run a couple of gallons through the system , then just drain the radiator. fill with distilled and you are good to go.
mk
Gee Mark, since there's only one inlet, and outlet to the rad, you're gonna have to help me understand why he won't see water flowing at the top hose, but will see it at the bottom? Or, conversely, 'splain why he will not see water flowing if the pump has failed.
I chose the top hose because it's easier to see, less mess to replace temporarily, and far easier to R&R.
"from the block to the rad as the t-stat opens."
I chose the top hose because it's easier to see, less mess to replace temporarily, and far easier to R&R.
"from the block to the rad as the t-stat opens."
02-07-2008, 08:59 PM
#39
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the upper radiator hose connects to the cross over. If you were to pull it, and the t-stat would be stuck or closed (cold) water is coming out of the heads and going down to the pump to be pushed through the engine. I guess if the pump is working , some water would be pushed out if the pump was running, but i dont know if it would be any faster than if it was just disconnected where water would fall out due to gravity.
mk
mk
This is not rocket science, water flows in the top of the rad, and out the bottom(when hot). There is no alternate place for it to go. If you can see flow at the bottom of the rad, it stands to reason that the same exact volume would be present in the top hose. What am I missing?
02-07-2008, 09:09 PM
#40
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first of all, i had to re-write the post to address just doing a clear plastic hose replacement. so, re-read that. second, if you read my original post, i said that on the lower radiator hose, where it connects to the t-stat housing, you need to jam-open the t-stat and replace. then at that point, it wouldnt matter if you disconnected the upper or lower. easier on the lower, due to the exiting water coming out of the existing hose and you pour water into a second hose that would attach to the t-stat housing.
If you do it your way, and the t-stat is stuck, you will not see any water movement. that is the main point. (even out of the lower as well)
you cant isolate the pump until you verify that the t-stat works and is open allowing flow to the radiator from the top of the engine to the top of the radiator and up to the t-stat housing. the next test would be to short circuit the radiator to see if it is clogged. take you plastic hose and just connect it to the t-stat housing hose with some type of joining pipe. then, you will have answered all possible questions.
Mk
If you do it your way, and the t-stat is stuck, you will not see any water movement. that is the main point. (even out of the lower as well)
you cant isolate the pump until you verify that the t-stat works and is open allowing flow to the radiator from the top of the engine to the top of the radiator and up to the t-stat housing. the next test would be to short circuit the radiator to see if it is clogged. take you plastic hose and just connect it to the t-stat housing hose with some type of joining pipe. then, you will have answered all possible questions.
Mk
That's all very interesting, but please answer my original question. We have a closed loop radiator. You tell me not to remove the upper hose, but to do the lower hose. I did not say 'pull it' I said replace the upper hose with a clear one. If the hose delivers hot water from the block/heads back to the rad, why would one not be able to see the same coolant flow as from the bottom hose?
This is not rocket science, water flows in the top of the rad, and out the bottom(when hot). There is no alternate place for it to go. If you can see flow at the bottom of the rad, it stands to reason that the same exact volume would be present in the top hose. What am I missing?
This is not rocket science, water flows in the top of the rad, and out the bottom(when hot). There is no alternate place for it to go. If you can see flow at the bottom of the rad, it stands to reason that the same exact volume would be present in the top hose. What am I missing?
02-07-2008, 09:17 PM
#41
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Sigh, I give up. If you can't explain why there will be flow in the bottom hose and not in the top, I stand by my original suggestion. R&R the top hose with clear, leave the cap loose, warm the engine look for flow. I gar-on-tee if there is flow in the bottom hose there will be exactly the same L/Min flow going through the top.
I'm done here.
I'm done here.
02-08-2008, 01:16 PM
#42
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Thanks for everyone's help! I do appreciate it.
Pretty conclusively proved that it's a bad water pump. PO installed a cheap one off eBay (probably fell for the "OEM Water Pump" description in the ad). Anyway, I took my old thermostat and "modified" it to be always open (as I don't have that secondary gasket mechanism in my car - actually pulled out the entire spring assembly leaving only the outer ring / housing so it would seal against the rubber O-ring) and still no water flow through the radiator, no heater heating up. Also the radiator is not clogged - if I pressurize the lower hose with the T-stat closed I get water flowing nicely out the upper hose.
Time to order a replacement. Fortunately, one of our forum sponsors is quite local to me...
Thanks again for all the help!
Pretty conclusively proved that it's a bad water pump. PO installed a cheap one off eBay (probably fell for the "OEM Water Pump" description in the ad). Anyway, I took my old thermostat and "modified" it to be always open (as I don't have that secondary gasket mechanism in my car - actually pulled out the entire spring assembly leaving only the outer ring / housing so it would seal against the rubber O-ring) and still no water flow through the radiator, no heater heating up. Also the radiator is not clogged - if I pressurize the lower hose with the T-stat closed I get water flowing nicely out the upper hose.
Time to order a replacement. Fortunately, one of our forum sponsors is quite local to me...
Thanks again for all the help!
02-08-2008, 02:04 PM
#43
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The T-stat is not just open/closed. It's more of a three-way, connects two ports when cold, closes one of those and connects the other to a third port when open. Maybe these will help:
02-18-2008, 08:53 PM
#44
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Update for those interested or with a similar problem: As suspected, water pump is bad. Impeller literally fell off the shaft when I removed the pump.
Should be back up and running later this week - the tensioner needs a new boot and so I'm going to rebuild it before putting everything back together. The rest of the parts in there look good.
Thanks again for everyone's help here, and a special shout-out to Dr. Bob who kindly lent me his 3/4" drive torque wrench as well as a couple other specialized tools to make the job easier. Thanks Bob!
Should be back up and running later this week - the tensioner needs a new boot and so I'm going to rebuild it before putting everything back together. The rest of the parts in there look good.
Thanks again for everyone's help here, and a special shout-out to Dr. Bob who kindly lent me his 3/4" drive torque wrench as well as a couple other specialized tools to make the job easier. Thanks Bob!
02-18-2008, 09:00 PM
#45
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Update for those interested or with a similar problem: As suspected, water pump is bad. Impeller literally fell off the shaft when I removed the pump.
Should be back up and running later this week - the tensioner needs a new boot and so I'm going to rebuild it before putting everything back together. The rest of the parts in there look good.
Thanks again for everyone's help here, and a special shout-out to Dr. Bob who kindly lent me his 3/4" drive torque wrench as well as a couple other specialized tools to make the job easier. Thanks Bob!
Should be back up and running later this week - the tensioner needs a new boot and so I'm going to rebuild it before putting everything back together. The rest of the parts in there look good.
Thanks again for everyone's help here, and a special shout-out to Dr. Bob who kindly lent me his 3/4" drive torque wrench as well as a couple other specialized tools to make the job easier. Thanks Bob!
I'd redo the timing belt while I was in there if I were you.
But that's just me.
H2