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Car's been running hot for a couple of weeks. I've changed thermostat, radiator cap, flushed out the radiator and nothing worked. It will get up to midway between the middle and HOT. It might drop a little, but will raise back up to that 3/4 line. Also, after running hot it is very difficult to start. It spins for quite a long time before starting and when it does start I have to give it lots of gas to keep it going. It runs terrible for about a minute and then runs fine.
Today, I spend the entire day replacing LIM gaskets. I could not believe how badly deteriorated those things were. I was certain that I had found the problem. After putting it all back together, it took quite a bit of cranking to get it to start. Had to Prime the fuel system I guess.
Followed all of the directions for filling up the cooling system and all seemed to go well. I did notice that it got up to temperature very quickly, but it always has. After less than 15 minutes of driving, the temperature gauge went to the 3/4 mark.
I replaced the temperature sensor today because I broke it when working on the car, so I'm sure it's an accurate reading. A couple of times, I've pulled over to a gas station and felt the hoses and it is definitely hot.
I'm out of ideas guys.
Again, in the last few months, I've replaced thermostat twice, radiator cap, flushed the cooling system and today I've replaced LIM gaskets.
Any ideas would be greatly appreciated.

when you did the flush was there any grit or anything in the fluid? still might be a plugged radiator or fans might not be working

Any ideas on a good way to flush it out? I used to use vinegar in the old days, but haven't tried that on this car. I've used different off the shelf flush products over the years and used one for this car, but didn't really get anything out that was noticeable.
Forgot to mention, since it's been running hot, I've just been putting water in it. When I drain it, it's perfectly clear. No water in oil either.

id water isn't the best thing to use straight cause of the antifreeze has 'oils' for the waterpump bearings at least from what ive done when doing flushes. you can try a reverse flush on the radiator but it might still be plugged in the fins. oh maybe the waterpump might be dead?

Are both fans running?

If the fans are running is the air coming off of them "hot"? If the air is just warm then possibly the radiator is partially plugged.

Yes, both fans are running.

Forgot the mention, but I replaced that 3 months ago.

Duplicate threads merged...

Thanks J.
No idea how I did that.

hi, from a cold start, with rad ap off, do you see the coolant swirling in the rad neck? also, are both the hoses hot after she warms up? if there is no swirl in neck, I would suspect the pump fins are rotten and is not moving fluid.

Perhaps the condenser/radiator is clogged up with debris? On the outside I mean. Could be affecting airflow.

Most likely possibility is some air trapped in the system.

Follow this procedure to bleed all the air out of the system

1)Fill radiator to base of filler neck.
Wait 2 minutes, then add, as needed.

2)Install pressure cap with arrows facing coolant overflow reservoir tube.

3)Put heater and AC controls in any position except Max and the temperature at the highest setting.

4)Start engine and allow to idle until the hose from radiator to water pump is hot.

5)Cycle engine speed up to 3000 RPM and back down about 5 times.
Slowly open the bleed valve for approximately 15 seconds to expel any trapped air.

6)Close bleed valve and shut car off.
When cooled to ambient temps, ensure that both the reservoir and the radiator are at proper levels.


Especially since you've used stop-leak in the system, radiator blockages are quite possible.
https://www.ericthecarguy.com/faq/what- ... strictions

Get an infrared thermometer and point it at various places on the radiator.
There shouldn't be any significant temperature differences, although the top will be somewhat hotter than the bottom


If the engine is otherwise running well and there are no external leaks, there are no trapped pockets of air and the coolant is definitely circulating throughout the entire system, then you either have warped heads or a blown head gasket or a restricted exhaust system or there was too much corrosion on the LIM for it to seal or the surfaces weren't properly prepared or the bolts were not torqued sequentially or to the proper torque.

In light of the serious overheats of the past, where your car shut itself off, a head gasket issue isn't out of the question.

Check the system with a pressure tester and see if the full system pressure holds for 5 minutes or so.
If not, there's a leak.

To check for restricted exhaust:
Attach a vacuum gauge
Reading should be steady and around 20 inches of vacuum.
Raise the engine speed to 2500 RPM and hold it there for a minute
The reading should have dropped initially, then gone back up to around 20 inches.
If the reading keeps dropping, your exhaust is restricted--crushed pipe or clogged converter.

Very thorough overheating troubleshooting video : https://www.ericthecarguy.com/faq/what- ... m-problems

After sitting all night, I topped off the water opened the bleeder valve to make sure the sytem was completely full. Cranked up and ran great for the 45 minute ride to my first stop. Once there, it sat for a couple of hours. When I went to crank it up, it it spun, but would not start. Appeared to not be getting fuel. I actually had to crank it for about 30 seconds several times before it started trying to start. I had to wait for it to start trying to start and press the pedal to keep it going. Once it started, it ran really rough for about 30 seconds and then seemed fine. Once I started going, I got the P0171 code. I had my scan tool, so I erased the code and it didn't come back. After about 20 minutes of driving, it started running hot again. I made it to my next stop and was there for a couple of hours. When I went to leave, it was cooled down, so I checked the water. Empty radiator. No sign of leaks anywhere. I filled it up, bleeding and making sure to let it sit and go back and top it off. Again, I had to crank several times for about 30 seconds and it seemed to not be getting gas. Finally cranked with the help of a little patting of the pedal when it was trying to start to get it to actually run. After a few minutes of driving I got the P0171 lean code again, erased it and it didn't come back. Close to my house it started to run hot again, never getting over the 3/4 mark. I made it home and got out and let it sit for a few hours. Everything under the hood still feels hot. Opened the cap, no water in the radiator.
Where's the water going? Why is it having such a hard time starting? There's no water in the oil and no oil in the water. Now that I think about it, as I was getting close to my house the temperature gauge actually returned to normal. I'm guessing now it's because there was no water in the system and the sensor only measures temperature of fluids. Once I get it filled up again and bleed all of the air out, I'll head to Autozone and see if they have a pressure tester to see if I can find where all the water is going. No steam, so I'm not burning it.
Help! Another day with my car giving me a fit. I need to be able to depend on this car to get me where I need to go. I have no back-up.
Thanks,

Okay, just left Autozone. Radiator pressure test went fine. No leak down. Radiator cap was pumped up to 15 pounds and dropped to 0 within a few seconds. So, I bought a radiator cap. One thing that really bothers me though, while playing around with the tool, I started my car with the radiator pressure tester on the radiator cap, and the pressure went up to over 30 pounds! I'm sure the water pump doesn't produce this kind of pressure. If I'm building up 30 pounds of pressure in my cooling system that tells me two things. 1. There's not a radiator cap made that will seal in that much pressure. 2. I've got a major engine problem if I have that much pressure in the cooling system. Just to check, I cooled it down, filled it with water and bled the air out and, I cranked up the car and let it run for a few minutes and even though the cap felt cool, when I opened it, it had a lot of pressure and blew out water.
Again, I don't have oil in my water or water in my oil. It seems like a head gasket pumping compression into the water jacket of a cylinder. But, if that's what's going on, why did I not have a pressure loss on the radiator pressure test when I pumped it up? That would have sent coolant directly into that cylinder, right?
I'm interested in your thoughts. I'm one step from buying some head gasket in a bottle and pouring that in there. I hate to use that stuff, but I've got to have a way to get to work.
Thanks for any help you can provide guys,

A lot of times pressure can enter the cooling system, but not the other way around..acts like a one way valve. Usually it's engine compression that is so high it gets out, but cooling system pressure isn't high enough to go the other way. If you built up to 30 PSI that quick, I'd look in your overflow tank and look for bubbles. What kind of condition was the seal on the radiator cap in? Also, there is a test kit for checking for combustion gasses in the cooling system that connects to the overflow. It has a chemical that reacts to combustion gasses and will change color if it detects them. You will be able to verify a combustion leak into your cooling that way. Otherwise a 4 gas analyzer can be used by poking the tail pipe sniffer into the overflow to see if there are exhaust gasses in the coolant as well ( just don't get it wet ).

Think about it, the pressure in the cooling system is 15 psi.
The compression in a cylinder is around 150 psi.
Huge difference.
You can very easily have no leak with a cooling system pressure test for just this reason.
You're right that there should never be 30 psi in the cooling system.
If you didn't pressurize the cooling system but had the gauge connected and the pressure rapidly rose to 30, I'd say the head and/or head gasket is damaged.
The only place for extra pressure to come from is the cylinder leaking pressure into the engine.
So it sounds like the head gasket is blown or the head is cracked or both.
Don't drive the car and don't try to start the car.
Remove the spark plugs and turn the engine by hand to expel the coolant from the cylinder/cylinders.
You can then do the compression test or a block test.
You can confirm it's the head gasket with a block tester-- which detects the presence of exhaust gases in the coolant.
You could instead do a compression test to confirm which cylinder or cylinders have low compression, which also tells you which cylinder is affected by the head gasket/head issue.
Where does the coolant go? Into the cylinder and out the exhaust as steam.
Coolant is not very compressible and if there's coolant in a cylinder, it can cause hard starting at the very least.
Serious additional engine damage can occur if the cylinder hydro locks---resulting in a bent connecting rod at the very least.

The cheapest option is to replace the head gaskets yourself and have the heads checked to ensure there are no cracks anywhere and then machined to restore them if warped.
It may be better, in the long run to just replace the engine with a low mileage junkyard engine..

Yeah, I'm pretty convinced it's a head gasket, but I'm a little confused. There's not steam and no oil in the water or water in the oil. I guess it's compression test time. Just replaced the transmission and two weeks later did the LIM gasket change. Getting a little tired of tearing this thing apart. I'm getting too old for this crap!

If there is no steam, no coolant in the oil, no oil in the coolant and no external leaks then your engine can't be losing coolant.
Perhaps the steam at idle is just not particularly noticeable.
Your exhaust should have at least some sweet coolant smell to it.
If you hadn't seen 30 psi buildup rapidly, I'd have thought you just had some trapped air in the system which, when released made the true, lower level of coolant plain to see.
You should be able to see which cylinders have coolant entering them by looking at the plugs.
The plugs which are beautifully white instead of having normal light tan deposits, are an indication of the coolant steam cleaning those plugs.

Yeah, I'd look at the plugs as well, at least when you do get into it, you can focus on those cylinders when you inspect them. You could very well be loosing coolant and not know it. I was going through a quart of oil ever fill up in my van and had no oil spots in my driveway ( obvious new ones at any rate ) and didn't get clouds of blue smoke that I could see, nor did I have any co workers mention it to me, which they would have since I see so many on the way to work everyday. Just because you don't see it, doesn't mean it's not happening. I was loosing brake fluid and couldn't find it until I got under the van with a light and started following the lines. The leak was in the line to the back, but it was squirting fluid on top of my gas tank, so there was never enough to drip down whenever I was parked, and then it would slough off as I drove. The only way to tell was the wetness of the line and the area around it.

Some Audi's are known to develop a pinhole leak on the top of the fuel pump assembly causing the smell of fuel to emanate from around the rear wheel....have fun finding that one if you didn't know where to look.