Matt O.

Ok, basically I'm having a hard time believing it's a head gasket. I threw the pressure tester on the resevoir, started the car, and it seemed to stabalize at 18 or so PSI, with the temp mark just below the FIRST thin bar (PERFECT!!). It stayed this way until I shut the car off, about 10 mins later, so it had PLENTY of time to warm up. The fans came on like perfect, and there was no noticable amount of moisture coming out the exhaust. Nothing more then the normal amount that comes out during an initial start-up.

So that makes me think it's a radiator cap now. If this pressure tester can hold the pressure from releasing my coolant out the overflow (and I rev'd and rev'd the engine for several minutes after warmup), then it's got to be the cap, right? I had purchased a new cap but I got it at the local auto store a few weeks back, so I'm thinking it needs to be OEM.

So I call up the place in Wilmington, and they close in 20 mins (I'm an hour away). So I pay over the phone and have the guy leave it in their car lot on a tire of some Infinity. Anyhow, I drive the hour to get it and get back home, pop that puppy on there and crank her up. After a whilte (longer then way back when) it does not hold the pressure, and overflows out the overflow valve.

BUT...

Now I think it's the RESEVOIR who is causing all my heartache. At least this portion of it. Because, it was leaking out of the TOP of the resevoir, something it hasn't done. Is this a common failure point? The coolant resevoir?

I really think if I pop a new resevoir on there my problem will be fixed. I've got a brand new OEM cap, and already did the fans/hoses/radiator brand new (fans were used but work great) so I can't see anything else I should be looking at.

So does the top of the resevoir commonly fail?

Thanks in advance,
Matt

Matt O.

bump

So would it be worth getting a new resevoir?

-M

Rob

[quote]it seemed to stabalize at 18 or so PSI<hr></blockquote>

What is the stock cap rated at? They normally marked on the top. IIRC they are only rated for about 15-16 psi, so 18 sounds too high to me. I hate to say it, but I would vote for the head gasket being the culprit. I've seen it before (not on 944 though) where a bad head gasket will causes these same problems.

Good Luck,
Rob

instigator

Matt you've got to have a air pocket in there somewhere thats steaming up to cause that kinda pressure if it was the head gasket it would more than likely be more psi on the gauge. now i know you have bled and bled till the cows came home, something else is amis, if all else fails try and find a 20psi cap and run with it for a while, changing out the reservour might help to eleminate bursting at that pressure but i think it could handle it <img src="confused.gif" border="0">

Matt O.

OK, so it's a head gasket and it's not? This is very crazy. Sometimes I lean towards the headgasket, sometimes I lean towards the air in the system. I vented the system as much as I could. I vented and vented and vented. Even when water/coolant was coming out of the vent at a steady pace I continued to vent, poured more water in the tank, and pumped it out, over and over. By the way, I did have the heater control set to full HOT with the key in the ON position. This is correct, right?

There is a place in Wilmington that seems to know what they are talking about. They serviced my car back in 89 when it was brand new, as seen by their stamp in the warranty booklet I have.

Anyway, they told me that can put a device on the coolant tank that will be able to tell if exhaust gases are getting in there, via a chemical reaction and something turns blue. I have no clue what, but that's what he said. He said if it was a head gasket, they will do a complete gasket change for $800 total. He said that includes ALL gaskets AND a new timing belt, because something about not wanting to retension the old one??? The PO told me he had these guys (Tony's Foreign Car, Wilmington NC) do the timing belt shortly before he sold it to me, but I received no records. If I was going to spend $500 on a new gasket set by the guys here in town, and Tony's in Wilmington will do that and a timing belt for $800, shouldn't I just get the timing belt done at Tony's?

They are in Wilmington as I said, about an hour away. We'd throw Argento on the back of a trailer and put the Expo to work tomorrow morning so they can check it out. Sound like a plan? I welcome any more advice/comments on this situation. I'm really at a loss, as I am not a professional wrench and would really have no clue how to do this myself. My dad has done this stuff before, but he would rather pay someone else to do it and know it's done right.

In case you were wondering, yes my dad is paying for this problem, but I don't want to just throw his money at the problem because I wouldn't do that if it was my money - his money is my money in this sense. I wouldn't waste mine, so I'm not going to waste his. Which is why I have taken this long to try to pinpoint exactly what it is, buy used parts, etc etc.

I digress.

Comments?

-Matt

Sasha

The other day, I went to a local independent porsche mechanic and he pressure tested my cooling system. It produced a small drop of coolant at about 18psi and then the pressure started dropping to about 15psi without apparent coolant loss - but this is another storry.Then he tested the cap. The cap held pressure much higher than his device could induce and he said that I needed a new cap. So I bought a new OEM cap (it has 150 stamped on it), drove it home and then to a store, and after I came out of the store, some of my coolant was on the ground... Aparently it leaked out of the overflow hose when the car was shut-off - presure built up and got released throught the OEM cap. I looked at my old cap and it is a Mercedes cap with 140 rating on it, the seal looked a little different, the Benz one was a little bit higher quality and different shape... I put it back and it ran/runs just fine.

So, may be your new cap is either faulty or "wrong" one for the car.

I have heard that you could test the head gasket with a smog machine: the smog machine probe will detect the HCs in the collant tank - I am not sure if there are smog stations in your area (the have them on every corner in Calif.), but this would be the easiest/cheapest way to check for your head gasket failure...

I have not heard of overfill tank failures...

It is a $60 descision which might not be the right one - remember the car is fine with the pressure tester on it. Sounds like a cap - call the closest Porsche dealership and ask them about the cap!

$800 for both gasket job and belts is a good price! I was qouted $500 for just the timing and balance shaft belts, water pump here runs about $800 parts and labor.

Hope my bubbling helps a little...

Thanks

Matt O.

That is awesome, thanks for your help.

Quick comment:

The pressure tester is good to I think just above 30 PSI. So, of course that would hold the pressure, but do I want a cap that can hold that high of pressure? Isn't that the whole idea of having a top pressure that the cap can hold being set by the factory (in this case 16 or so), so if something HAS to give, it's the cap/overflow and not your radiator or worse more expensive things?

I could run all day probably with a radiator cap that could hold 50 PSI, but I would probably spring leaks everywhere else. Wouldn't you think?

My OEM cap looks the exact same as the one that was one it since I purchased, which has worked like a champ until this problem started. Never had any overflow/overheat problems until this past december (besides a themo problem that was promptly fixed.)

Anyway, thanks for the input.

-Matt

jason952

Matt: [quote] By the way, I did have the heater control set to full HOT with the key in the ON position. This is correct, right? <hr></blockquote>

May be a bad question, but you do have the engine running right? Sounded like the ignition was only on.


Jason

Riff

Hey Matt-

Here is another option that I have heard about. Let me get this straight first: Car begins to overheat, but only when it is driven. When idling in your garage, the temp rises but does not go above first line, no where near overheating??

Does this describe the situation accurately??

If so, this is something I read once, back when this was Porschefans. The above situation was what was happening to someone's car. Turned out that the waterpump impellor had seperated from the driving shaft. At idle, there was enough friction between the shaft/impellor to turn the impellor and move the coolant. But as speeds elevated, the shaft just spun and the impellor stopped. The coolant went nowhere which led to the overheating! Does this sound like what you are experiencing? If so, then you should just replace the waterpump.

Let us now how it goes.

HTH

Tom R.

matt,
I had the following problem with my 86 rx7 in the summer of 91:

I flushed the radiator and changed the fluid.

i then took the car on a 400 mile drive to. about 125 miles into the drive i heard a loud buzzing. turns out the second gen rx7's have a low coolant warning buzzer.

after stopping 5 times to top off the coolant i said the hell with it and put in a whitesnake cd and blasted it louder than the buzzer for about 100 miles.

the next monday I took it to the mazda dealer in burlington vt.

turns out the return at the bottom of the overlow tank has some sort of valve that got stuck. motor would get hot, a littl coolant would go into the overflow tank, none would go back into the bottom, then the buzzer would go on.

you get the idea?

Good luck

Matt O.

[quote]Originally posted by Riff:
<strong>Hey Matt-

Here is another option that I have heard about. Let me get this straight first: Car begins to overheat, but only when it is driven. When idling in your garage, the temp rises but does not go above first line, no where near overheating??

Does this describe the situation accurately??

Let us now how it goes.

HTH</strong><hr></blockquote>

Thanks very much. If the exhaust doesn't show up in the test on the coolant tank, then I will definately have the water pump replaced. I hope that's the only thing, that would be much cheaper. That and the timing belt.

To Jason:

I was under the instruction and assumption that you do not start the engine when you vent the system, you just turn to full HOT with the key in the ON position. As seen at <a href="http://garage.type944.com" target="_blank">http://garage.type944.com</a> coolant venting instructions.

Thanks,
Matt

billybones

Let me give this a shot, Is the car on level ground when you are done filling it? IF it is on an incline when filling it. the lines on the tank are not true.. you will expell excess fluid when driving. You never say anything about the temp? just fluid loss.. The manual says to actually finnish your fill with a hot engine. up to the hot line.(obviously leave the cap off till temp is reached) Where is the fluid level when hot? and level on the ground. I had a bad head gasket that would slowly overheat the water while extended driving. this was on a toyota though..hope this helps.

Matt O.

[quote]Originally posted by billybones:
<strong>Let me give this a shot, Is the car on level ground when you are done filling it? IF it is on an incline when filling it. the lines on the tank are not true.. you will expell excess fluid when driving. You never say anything about the temp? just fluid loss.. The manual says to actually finnish your fill with a hot engine. up to the hot line.(obviously leave the cap off till temp is reached) Where is the fluid level when hot? and level on the ground. I had a bad head gasket that would slowly overheat the water while extended driving. this was on a toyota though..hope this helps.</strong><hr></blockquote>

I've done it both with the car on level ground and an incline. The instructions actually say an incline is better...?? When I filled it on an incline I took that into consideration and only filled to the min mark. As stated, I have also filled and vented while level, same results.

I did finish filling once with a hot engine and got the same result. I am going to try to vent it all once more to see what I can see, but I'm afraid that this is going to be one of those times Auchum's (sp??) razor is proved wrong.

Thanks a ton,
Matt

IBRJA

Just a thought guys, because it happened to me on another vehicle and it took 2 years to figure it out completely.
Your problem of overheading under a load (while driving it) could be caused by a poor or bad fuel injector. I had one that would spray to the side and dribble fuel in spurts while the others sprayed straight and true. I had someone test it on a hand pump set up. He srcewed the individual injector into a tool that had a small fuel reservoir and a hand pump to put pressure into the injector (because the pressure has to be at a certain level before the fuel will be allowed to be sent through the injector). This unit also had a pressure gauge on it to measure the pressure at which the injector would release or spray the fuel through it. Long story short, we locqted a bad injector. Apparently it caused my overheating problems for all that time. Check it out. It's not expensive to do, unless you break an injector as you remove it. The other method is to switch out all your injectors for known good ones and then run it. Hope this helps.

triscadek

My previous experienceis that air needs to be bled with the engine running, I've done mine 3 or 4 times with sucess that way. I've also been told by a mech. that you can take a sample of coolant from the car to a shop and they can test it for exhaust gasses without having to drive it down.