Ad0911

My car had a blown headgasket after overheating (traffic jam, hot weather). The mechanical fan worked properly but the aircofan did not spin due to failing thermostat switch (airco not working too). The being an aluminium engine, it is possible that somewhere in it's life the cooling liquid wasn't the required liquid for aluminium engines but perhaps topped up with tap water (thanks PO). This could have resulted in aluminium deposits clogging the cooling system. The car had a relative new radiator but the clogging up could have occured after fitting the new rad. Is there a way to determine if the system is clean inside? Can I take it apart for inspection? I would love my engine to cool properly once it hits the streets again!

WallyP

There are many possible causes for overheating. Some of these include:

- Slipping fan clutch. It is not unusual for the silicone-filled fan clutch to slip excessively. There is not a really good test for its proper function. One reasonable test is to get the engine up to normal operating temp; raise the bonnet on the idling engine and then increase the engine speed to about 2000 rpm and hold it there. After a few seconds, there should be a very noticeable increase in air flow and noise level from the mechanical fan. The fan clutch can be refilled without too much difficulty.
- Faulty thermostat operation. The thermostat operation on a 928 is very different from most cars. It is critical that the thermostat block off the passage behind the thermostat when the engine gets hot. The seating area can get eroded or damaged, allowing too much coolant flow bypassing the radiator.
- Faulty radiator operation. There should be a metal tube at the upper radiator hose entry to spread the entering coolant flow over the entire radiator. It is common for this tube to be missing or damaged, allowing most of the coolant to flow only thru the top of the radiator. It is possible for the radiator to be partially plugged, reducing cooling capability. You can try to check for event temperature gradients over the entire face of the radiator, but that is a little difficult to do with the A/C condenser in the way. You can flush and reverse-flush the radiator with a garden hose to help a bit.
- Poor air flow management. If the lower engine pan (the aluminum shield between the bottom of the radiator and the oil pan) is missing, hot air from the radiator can flow to the front and back thru the radiator again. This can increase overheating while stopped and at low speed. It is common to have crud built up between the A/C condenser and the radiator, which can greatly hamper cooling at low speed.

There are many other possible causes for overheating, such as improper ignition timing, improper fuel/air ratio, faulty water pump, etc., etc.

Removing the radiator will allow you to clean the matrix for better air flow and to flush it to check coolant flow. Doing so might increase your peace of mind.

Landseer

Our 85 was helped by three things, two mentioned above.

Reverse flush w/ garden hose ( but with mega shop vac pulling on the normal inlet hose)
Refilled fan with silicon fluid.
Found the body of an ancient radar detector blocking substantial area of the radiator.

NoVector

I wonder if your PO had a problem with your head leak and used some stop leak product? I think that was the case on my 84. Soon after buying it, I used some cooling system flush and next thing I knew, I was having leaks all over the place. Also started having white whisps of steam from the tail pipe, etc. And, coolant back-leaking into the trans-cooler in the side tank! I ended up replacing the radiator with an all aluminium Ron Davis one from Devek, replacing the head gaskets, and a couple flushings of the transmission. At the time, I was REALLY hating Porsche for ever getting into the water cooled engine business. When I did the heads, I couldn't believe how that stop leak crap gums up everywhere. I could see if some of that was in your system it getting into your new radiator and clogging up the paths of least resistance.

blown 87

Somebody put something more than run of the mill stop leak in yours if it was all gummed up like I think you are talking about, I have been in a lot of engines that have had regular stop leak in them and you can not tell it inside the engine.

NoVector

Wow! You're the first person I've ever heard say that. Here's a picture of the mess I had. That gooey crap that looks like... well, let's just say it was like Elmer's glue, was all over in the nooks/crannys. Maybe Ron Jeremy was the PO

NoVector

Oh, but it did clean up okay...

Trip..

That's what happens when people don't read the directions. Bars leak contains Sodium Silicate, AKA Water Glass. This is NOT compatible with antifreeze. If the coolant was not flushed completely, the cooling jackets will seal up like in the the first pic you attached. It can be fixed most times though, see below.

The OP asked what may be wrong? Well, chances are you to have Bars leak in your cooling system. The best way to tell is to drain the coolant and look for copper colored flakes, it looks like glitter. If you see it, then at least you know where to start. You don't have to drain the entire system, just start and drive the car long enough to get heat out of the vents, open the rad cap and check to see if the coolant has copper specks in it. If it's been in there for years, the coolant will look like rust or just really dirty brown coolant.

OK HANG ON! DON"T BLOW 200 DEGREE COOLANT IN YOUR FACE!!! Squeeze the upper hose to be sure it isn't hard, if it is, the system is under pressure, removing the rad cap will cause you to have a very crappy day! (2nd or 3rd degree burns can be disfiguring, please be safe!) If the upper hose is able to be squeezed, slowly open the cap being sure to allow the built up pressure to flow into the overflow tank. Even after the pressure is released, open the cap in such a way that the coolant would be deflected away from you.

Look for copper sparkles. If you have them, drain and flush, drain and flush, drain and flush... Most of the bars leak will come out. Refill the cooling system with straight water and drive for about 15-20 miles and vary your speed, but be sure to get the revs up a few times. Then drain and flush a few more times...

Just remember though, there was a reason for the can of Bars leak in the first place. So as you get all that crap flushed out, you may find all kinds of leaks. Most likely will be head gaskets, heater core, and rad leaks. So be prepared to fix the problems that the Bars leak has been hiding. That could even mean a cracked head! Yes Sodium Silicate will seal a severely cracked head, even in turbo/super charged situations. As long as the pressure is below 5000 PSI.

There really is no need to waste money on the Prestone coolant flush stuff, I've never found it to do much of anything aside from flushing 5 bux from my wallet. It's up to you. I will add though, I've heard that the flush can cause potential problems later on, again I've never noticed it to do much of anything good or bad. But these are my personal results.

Sodium Silicate isn't all bad, in fact Chrysler coolant comes with it right from the factory, so did/does Zerex. Anybody remember the old Zerex commercial with them pounding nails through the antifreeze bottle and the leaks stopping? They use it to stop leaks as they happen. The problem is, normal antifreeze isn't compatible with the sodium silicate, when the two are mixed, it makes a nasty crystal-like compound that plugs up every single water-passage in your cooling system, that's why sodium silicate has such a bad reputation in the first place.
As a side note, sodium silicate was used to protect eggs from rotting back before refrigeration... ...Man I wish I wasn't so full of useless knowledge...

I've only had one motor that I couldn't clear out the Bars-Leak, but that motor was completely packed full of the stuff, the customer said she dumped in 10 cans of the crap and topped it off with straight antifreeze!!! Why? ...And i quote... "Well, the guy at Autozone told me one can works pretty well, but 5 would be better and 10 would make the problem disappear"!!!

Back to the OP, Fix the fan problems and don't worry too much about the Bars Leak, yes it should be removed, but as long as you have good airflow, the Bars-Leak shouldn't hinder cooling too badly IMHO.

That shop vac treatment is a good idea, I've always used Compressed air, but I bet the mixture of the two would be fantastic! Although, bleach, toilet bowl cleaner (The Works) and Easy Off have always been my fall back in bad situations.

If you have a slight rad leak, a whole can of black pepper will seal up most leaks and it won't plug your heater core. Dump in a can, then go for at least a 20 mile drive, 50 would be better. Again this is something I have used in the past. I have an old beater S10 Blazer with 250,000+ miles that's living with pepper and a touch of sodium silicate in it's rad... I have good heat and my head gaskets don't leak anymore. But this is a $400 truck, not a Porsche...

Best of luck!

nsantolick

The Mercedes forum crowd seems to really push for proper "citric acid flushes" wherein one dilutes a few POUNDS of citric acid, followed or combined with dishwasher soap and several water flushes afterwards, each frequently involving an hour plus of actual driving. I can't see how that'd hurt, and it does appear to do a stellar job.

I'm about to flush my car and was debating doing just this. Anyone here ever try it? My car has sat drained of coolant for around 1 1/2 years, after the last shop put in the wrong coolant. I have a few gallons of Mercedes brand coolant waiting and couldn't find anything promising at the local automotive chain stores. I'd hate to not do a top notch job flushing after all that...

Ad0911

Well, thank you for all your good advice. I guess I am guilty too, because long ago I put a can of bar's leaks in a VW rabbit diesel. My 928 didn't have the gum inide. It ws pretty clen actually. Only the headgasket was so brittle it came apart in pieces when I lifted the heads. It stuck partly to the heads, partly to the engine. Guess where the debris went? What probably did contribute to the overheating problem was the fact that the hose with the heater valve for the interior heater core was plugged with a solid metal rod because the valve was faulty. Dear me for not testing the heater in mid summer when I bought the OB!

mark kibort

bars stop leak works great, ONLY on outward leakng head gasket leaks, not the internal types that allow exhaust gasses escape out of the compression ring.
it IS compatable with antifreeze and will not hurt a radiaotor. I used it, i used it with long life coolant, and it stopped a HUGE leak outward from the headgasket. pulled the engine, it was perfect, only stained a little red from the Barrs. there is another Barrs and stronger headgasket stuff, that has other ingredients, that might not work with our engines. Im talking barrs stop leak. gray bottle.

Mark

Trip..

http://www.barsproducts.com/1100.htm

Read the tech on their site and the many warnings on the bottle as well as all over the site...

Flush out the coolant. Leaving the coolant will cause all sorts of problems. However there are a few variants of Bar's leak. There are some that don't require you to drain the coolant. These are usually more expensive and don't work as well in my experience. Best thing to do is fix the job properly, dumping a mechanic in a bottle into your cooling system is a band-aid.

B/L will work on head gaskets, even gasket failure the allows exhaust gasses to escape the ring. My Blazer was burning a gallon/day, it would nearly lock the cyl in the mornings. I followed the directions on the bottle (in the link) and it's worked just fine. The water level has stayed in the same place for a few thousand miles. Is it fixed, no. Did it keep it out of the junkyard for awhile longer, yes.
Your results may vary.

mark kibort

I think the problem with this one, was the copper Barr's stop leak stuff that needs to be added to flushed coolant, then run for 30mins and then fushed again. maybe someone left that stuff in there. this is the stuff for cracked blocks, etc. its a milkshake of copper stuff and other fluid. the barrs stopleak is just a milky red liquid that is actually fine for any car, any antifreeze and doesnt clog anythig up, ever. it only seals leaks as it is forced out small holes and cracks, like a headgasket outward leak. otherwise, it is nothing more than water pump lubricant.