I am soon going to have to rely on my 951 and I've been getting all the problems worked out so I have a reliable daily driver. Finally had things settled so I thought so got some new tires and the last on the list was to get the A/C working to battle this Texas heat.

Well, long story, but my wife drove the car home from Zim's after they replaced the compressor and all that and got the A/C working again. They made a note on the paperwork saying that my heat flap was not closing because some motor wasn't getting the vacuum signal to close the flap, so they had to remove some rod to force the flap shut so that I wouldn't have heat coming in and negating the cold air from the a/c. I've heard about this flap before, but wasn't aware I had the problem because I've always just kept my vent fan on "2" and let ventilation air come in while I drove with the windows down -- and I've never noticed any heat coming in other than just warm air from not having a/c working. So, I was a little frustrated by that... but I guess I won't be needing my heater for a while anyway so I have some time to worry about that later on.... So -- my heater flap or whatever it's called is forced closed from what I gathered from the tech.

Now, so my wife drove the car home and it sat for the weekend. I got up Monday and drove it to work and noticed the coolant temps were getting up there and the stock gauge was getting up to the upper white line... and I have always seen my temps only hover just over the lower white line so I pulled over and checked my coolant level... a little low but now visible leaking anywhere..I let it cool down and went on in to work a few more miles. On the way home however, the needle got further up and got above the upper white line, but not into the red. By the time I pulled over it was leaking coolant. A pretty small but constant stream from around the middle of the motor and no spray on top / no visible residue on the top of the motor..

I called Zim's who had just had the car like I said and babied it up to their shop after putting distilled water in and leaving the reservoir cap on but loose (as advised by the service manager).

They had the car for 4 days and came up with all kinds of issues that they think could be causing the leaks / hi temp readings.... this is basically the order of how things went.. i'm trying to find out what may be wrong and what maybe is being overlooked. ???

1) wrong reservoir cap - replaced with new one (mine was only a 12psi cap and they put a 1.5 bar cap on it)
2) he said I had a leak in the radiator - $1100 (but then it healed itself? because. ...the next day it was no longer leaking and he let it run for 30 minutes at idle and not a drop.. so we did not replace the radiator he sees residue down the side of the radiator, but unsure if it is from the radiator
4) he thinks it might be a bad thermostat... even though they replaced it 4 months ago along with multiple water hoses and the water pump
5) he replaced the thermostat and that didn't fix it
6) he drove it 3 times the next day and it never overheated until he got it right back by the shop and the temps "went up very quickly" so he thinks that there's now way it can change that fast so he thinks it is the temp sending unit
7) replaced temp sending unit and called me to pick it up cause now it's fine

so, I picked up the car after all that, they replaced the coolant tank cap and the temp sending unit, charged me $350 and sent me off.. I get 7 miles down the road and the temps are getting up close to the upper white line again (A/C blows cold though). I took a picture of the gauge including my mileage and called them and told them... unfortunately their 944 guy is out all next week so I can bring it back and let it sit or bring it back in a week...

Sorry for the long post, but I wanted to be detailed. I need this car working in no more than 2 weeks and I'm getting down to the wire with my patience and my budget.

Here are my 2 theories.. I am going to do further testing tomorrow but here is what I have now..

1) Air bubble in the coolant -- causing quick temp changes. I know that I was seeing bubbles coming up into the coolant tank while the car is idling and espescially when I push the throttle several dime / quarter size bubbles come through into the tank from the bottom... that would have to mean air in there right? I showed the tech this at Zim's and he said he had "burped" it several times and I watched him do it, but he didn't elevate the front of the car. I mentioned this method and he said he wanted to try that also, but that he usually doesn't need to on 944s he said.. I watched him jack the front of the car up, but only the driver side so the driver side was higher than the pass. side.. I don't think this is the idea though because the bleed screw is on the passenger side! ??? so not sure if he was bleeding it right and I'm going to do this first thing tomorrow following the method on clarks-garage...

Along with this theory, obviously my temp sending unit was not faulty

2) whatever "rod" the tech removed to keep hot air from overpowering my cold A/C air is also keeping the hot air from the motor from escaping where it needs to go? and when I turn on the A/C the temps get hotter and hotter because the heat has no where to go? The reason I'm thinking this is because I do notice the temps start to cool off when I turn off the A/C, but I haven't had time to test this out much so I will be testing this out more also... Also, the only thing that changed from before I had the A/C fixed was that a) the a/c compressor is producing heat that wasn't there before and b) this heat flap thing that he said he is now forcing closed... what is the plumming on that heat flap? I need to figure out how to reverse what he did so I can test if that is causing extra heat buildup when my a/c is on...

sub-theory... the only time i had coolant leaking was on the way home from work. and then over to the shop shortly after that same day, it never leaked while in the shop the last 4 days... I'm thinking the leak was because it was so hot that the extra pressure caused the coolant to seep out of some hose that may not have been tightened down as much as it should have been and the coolant / pressure found a way out that way.. as soon as the pressure went down enough, it stopped leaking. So, I don't think I have a coolant leak parsee, just had a leak because of the heat that day.. so really just need to find the source for the overheating.

i now apologize for taking up 30 minutes of your life!!!

 

Rapid temperature changes would be consistent with air in the coolant. Does it overheat w/o the AC running or just when the AC is on? If the AC system is overcharged it can make the compressor work extra hard and get nice and hot. I'm no AC expert so hopefully others will chime in but I think you want to be running ~30-35psi on the low side at 2k rpm's.

The 'heat flap' they're referring to is just the vent inside the cabin that controls hot air flow. There's $2 clip that fails on the rod they mentioned that keeps the flap from closing. Since it's just climate control air won't have anything to do with your engine overheating but might make your feet overheat

 

Danny, check out my recent posts on this issue. I ended up without a thermostat to cure the issue (after having 3 bad ones). Although it does sound a bit like air in the system. I really prefer the vacuum approach or a pressure tester approach with the front end up on jack stands.

Here is one of my threads, but there are others under my name as well.

https://rennlist.com/forums/showthre...ht=running+hot

A couple of thoughts come to mind if it is not air in the system;

Have you pressure tested the system to make sure that it is not a bad hose somewhere that has a pin hole leak in it?

How clean are the fins in the condenser and radiator?

Are the fans working properly? Did they change the condenser when they did the A/C. If so, I vaguely recall that the fan connectors can be reversed (but am not sure) and if they are they will push hot air through the rad as opposed to suck cold air through.

 

Water pump? Check the upper and lower hoses to make sure they are hot, indicating that that coolant is flowing through them. Could also be the sending unit for the radiator fans is bad and not telling the fans to turn on soon enough. Pressure testing is always a good way to find a leak if there is one. $1100 for a radiator??? That sounds way high to me.

 

Drove it some more last night with ambient temps around 95 F. Before turning the a/c on, I drove it probably 10 miles and got the temps up to just over the lower white line, right where I expect to see it and where I usually see it (prior to these issues). Got on the highway and drove it spiritedly and also on a slow back road and at a few stop lights, no heating issue at all..

..then I decided to turn on the a/c and see what happened... almost instantly, as in, within a few minutes, the temps creeped up toward the upper hash, say about 1/8" under the upper white line, just by turning on the a/c.

So, I'm thinking something is up with the a/c. Can anyone confirm Greg's advise above?

 

Thanks for the link. very good info!

The condenser was not changed. I'm not sure about the fins on it, but note above, now I know that it only overheats when the a/c compressor is on. This was not an issue last summer which was the last time my a/c worked. I'm pretty sure now espescially after driving it again last night and not seeing any leaks other than the compressor condensation, that the leaking i saw before was just from the built up pressure from the coolant being overheated and I probably have a hose that is not clamped down as tight as it should be. Probably an upper hose seeing as how the coolant leaked down the driver-side of the radiator.

 

Have u verified the radiator fans come on when the ac is turned on ?
When the temps get to where u consider it too hot are the fans on ?
My temp gauge gets to the last normal mark, that's when my fans turn on and the temp quickley drops to the center mark. With my "new" ac on my temp stays in the middle. Air in the coolant will make your temp erratic. Your coolant valve should be closed preventing flow thru the heater core, so I wouldn't think the flap for air flow would be an issue. Heater coolant Valve closed requires vacuum.

 

update: the radiator fans are working properly
replaced the thermostat,
replaced temp sending unit
replaced coolant tank cap (mine was leaking)
bled the coolant several times both with vacuum and with the nose in the air
found melted vacuum line that controls heater valve (fails open) and replaced
checked a/c pressure and was told it never got over 290 and 400 is bad (not sure what that means)
was told that upper and lower radiator hoses are running same temps which was 186F at the time.
was told that my radiator is the only thing left to replace

car still runs hot with a/c on but stays around 9 o'clock or down to first white line when a/c is off. I'm suspecting I've got two bad thermostats (first one replaced ~6 months ago when water pump was replaced, but prior to getting a/c working. 2nd one was put in last week.) The shop that replaced them did not test them to my knowledge prior to installing them.

 

If your thermostat was bad then the upper and lower hoses would be different temps because the coolant wouldn't be flowing through them. The low side pressure on the A/C system should be lower than 40 psi and the high side depends on the ambiant temp. to figure out. If I remember correctly, the high side pressure should be the ambiant temp times three. So if it was 90 out then the high side pressure should be around 270, which sounds like what yours was. Could just be the radiator not being effective enough to handle the extra load of the A/C system.

 

I thought if the coolant was flowing through the radiator, and if the radiator was working properly, then the upper and lower hose would differ by a large bit, like 20-40 degrees. hot water in and it cools a little before it goes back out, right?

 

If your radiator is working well than yes. If the thermostat wasn't opening then the lower hose wouldn't flow coolant, which would cause the car car to overheat with or without the A/C being on. If both hoses are the same temp. when the shop measured them, then it sounds like your radiator isn't effective enough to remove the heat that the engine produces.

 

The radiator sounds like the culprit based on what your are describing. The a/c condensor puts off heat, so if your radiator is old and partially clogged, this could cause the symptoms you are having.

I am having sticker shock at $1,100 for a new radiator. Guess I have been doing my own work for too long. Is the shop going to give you some relief for the previous incorrect guess and repair?

 

$1100?! NFW. 944online has new radiators for $410, but I don't know if they're OEM or not.

 

Paragon has radiators for 412.00
This 1100.00 must be a quote for new rad plus install?

 

radiator, new hoses, clamps, latte's and labor too. the last radiator i bought a few years ago was $300 from 944 online.