Strange S4 cooling problem - New Pump Failure
03-22-2009, 01:01 PM
#1
Advanced
Thread Starter
Join Date: Jan 2009
Location: Barrie, Canada
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
Strange S4 cooling problem - New Pump Failure
Problem solved - New pump failed - Impeller came off the shaft - fixed with a new new upgraded Laso - Thanks Roger from 928sRus!!
(Original Thread)
I have a 1987 S4, 180,000 m. just did pump/cambelt (successful).
New thermostat, gasket rear seal and rad cap.
The cooling system is fine in the garage. heats up, stays at temp, holds pressure cooling fans cycle as they should, flaps disengaged 100% open, rev engine is OK and the system is fully bled.
45 second into a drive coolant pours out of rad cap . The temp gauge didn't move up or down (needle at 2nd thin white line) during the 45 seconds.
Bring it back to the garage, turn engine off - the expansion tank is full of water and air/gas is bubbling back to the tank from both return lines.
Start engine again, loss about 2 liters of fluid, engine stable at idle and revs OK.
I think its the head gasket with a very small leak -It leaks only under load = higher pressure in piston - leaks into coolant only.
Coolant (mainly water) was black/grey before this test (drove 15 minutes in this condition when it 1st happened).
No white steam out back because the leak is too tight for low pressure.
All pistons are 170-185 psi compression test (throttle closed)
Attached is a monitoring chart of the system for 1 hour in my garage before the "45 second" road test.
I am going to take the engine/pump apart - if some one thinks it something else let me know
John M
(Original Thread)
I have a 1987 S4, 180,000 m. just did pump/cambelt (successful).
New thermostat, gasket rear seal and rad cap.
The cooling system is fine in the garage. heats up, stays at temp, holds pressure cooling fans cycle as they should, flaps disengaged 100% open, rev engine is OK and the system is fully bled.
45 second into a drive coolant pours out of rad cap . The temp gauge didn't move up or down (needle at 2nd thin white line) during the 45 seconds.
Bring it back to the garage, turn engine off - the expansion tank is full of water and air/gas is bubbling back to the tank from both return lines.
Start engine again, loss about 2 liters of fluid, engine stable at idle and revs OK.
I think its the head gasket with a very small leak -It leaks only under load = higher pressure in piston - leaks into coolant only.
Coolant (mainly water) was black/grey before this test (drove 15 minutes in this condition when it 1st happened).
No white steam out back because the leak is too tight for low pressure.
All pistons are 170-185 psi compression test (throttle closed)
Attached is a monitoring chart of the system for 1 hour in my garage before the "45 second" road test.
I am going to take the engine/pump apart - if some one thinks it something else let me know
John M
Last edited by Rocketman928; 12-29-2011 at 10:26 PM.
03-22-2009, 01:23 PM
#2
Rest in Peace
Rennlist Member
Rennlist Member
Join Date: May 2006
Location: Bird lover in Sharpsburg
Posts: 9,903
Likes: 0
Received 2 Likes
on
2 Posts
find a shop that has a block check device, or buy one yourself, they are not much, about 60 bucks for a good dual chamber one.
It will test for hydrocarbons in the cooling system.
It will test for hydrocarbons in the cooling system.
03-22-2009, 04:59 PM
#3
Advanced
Thread Starter
Join Date: Jan 2009
Location: Barrie, Canada
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
F*@#!ng new water pump failed
In the beginning, when trying to diagnose the problem, I revved the engine and didn't feel any pressure in the pump discharge line. Thought it was a pump failure.
I modified a web cam, put it in the thermostat hole and my wife turned the motor.
It spun - it was new - was an original Porsche casting rebuilt in Germany -with a cast iron impeller.
I guess at slow speeds it spun a little - enough to recirculate water.
The loose impeller has machined (ground) down a nice 1/8" extra pump clearance.
I don't think a new pump will pump as well with that amount of clearance.
I think i need to modify a pump to fit in the "new housing". If I drill a hole through the impeller and through the impeller for a dowel pin, I can move the impeller forward to get then clearance down to a reasonable amount.
Or I can have a replacement piece machined to replace whats missing and countersink-bolt it in place.
Am I the proud owner of a 5.0L Porsche boat anchor?
Has anyone fixed this "new" problem I have now.
Thanks
John M
I modified a web cam, put it in the thermostat hole and my wife turned the motor.
It spun - it was new - was an original Porsche casting rebuilt in Germany -with a cast iron impeller.
I guess at slow speeds it spun a little - enough to recirculate water.
The loose impeller has machined (ground) down a nice 1/8" extra pump clearance.
I don't think a new pump will pump as well with that amount of clearance.
I think i need to modify a pump to fit in the "new housing". If I drill a hole through the impeller and through the impeller for a dowel pin, I can move the impeller forward to get then clearance down to a reasonable amount.
Or I can have a replacement piece machined to replace whats missing and countersink-bolt it in place.
Am I the proud owner of a 5.0L Porsche boat anchor?
Has anyone fixed this "new" problem I have now.
Thanks
John M
Trending Topics
03-22-2009, 08:06 PM
#13
Rest in Peace
Rennlist Member
Rennlist Member
Join Date: May 2006
Location: Bird lover in Sharpsburg
Posts: 9,903
Likes: 0
Received 2 Likes
on
2 Posts
Mine was a new Lasso at the time, two years ago, I am only going to run the plastic impeller Porsche rebuilts from now on.
I have no idea if it is a new or old style pump.
I have no idea if it is a new or old style pump.
03-22-2009, 08:59 PM
#14
Basic Sponsor
Rennlist
Site Sponsor
Rennlist
Site Sponsor
The pump was a rebuild from a local Canadian supplier.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
03-22-2009, 09:23 PM
#15
Three Wheelin'
you mean the rebuilt Porsche pump.
Gregs pump is a new Lasso, with only 3000 miles. I cant make sense of how it could have come loose. I thought that would only happen to rebuilt lasso. was it like 0.5 % failing rate for rebuilt ones.
is this the first time a new lasso has failed like this ?
also I thought you would hear the pump going out long before it does that to the block, it looks like they did not hear anything until the damage was done !!!
Gregs pump is a new Lasso, with only 3000 miles. I cant make sense of how it could have come loose. I thought that would only happen to rebuilt lasso. was it like 0.5 % failing rate for rebuilt ones.
is this the first time a new lasso has failed like this ?
also I thought you would hear the pump going out long before it does that to the block, it looks like they did not hear anything until the damage was done !!!