I live in Miami, where it is usually high 80's or low 90's outside, with
high humidity. My car runs at the top white line in stop and go traffic,
but runs cooler on the highway. It used to run cooler. It started running hot last year, and shortly thereafter the headgasket blew (water out exhaust).

1. The waterpump is about two years old -- updated version.
2. Tested thermo switch on radiator --ok.
3. Replaced temp sender in head.
4. Jumped the fan connector to run them both on high -- still ran hot.
5. Replaced head gasket (some cylinder scoring, but no visible cracks).
6. Had machine shop re-spec head.
7. Replaced radiator.
8. Replaced thermostat.
9. Confirmed base seal in pump is ok.
10. All new hoses.
11. Mostly water mixture with Water Wetter.
12. Bled it and bled it and bled it and bled it...
13. New resevoir and cap.

It seems like there is not enough flow. I am curious about the bypass
system in the pump. How can I tell if my thermostat is for the later
waterpump version? If I use the early thermostat with the later pump,
will it run hot because the bypass plate is too short?

What now?

 

Next step is to make sure your gauge is telling the truth...

Deteriorating grounds are a cronic problem and will cause your gauge to fluctuate and read incorrectly. Clean up all the grounds that relate to your instruments, including the main engine ground (between the battery compartment and the back of the block). The one to concentrate on is in the driver side foot well, close to the firewall on the outside of the car.

There's also a proceedure described on the Paragon (I think) website for cleaning the contacts inside the gauge cluster.

I also posted a little while ago a link to very neat vacuum tool for filling cooling systems... seems to work much better than either manual or pressure bleeding. http://www.thetoolwarehouse.net/shop/UV-550500.html

Good luck.

 

My car is going through the exact same problem and I've replaced just about all the same parts... I can confirm it's running hot because the NOX level in last month's emissions test was through the roof (~4x the limit). It was fine just two months earlier...

Cleaning the grounds is a good idea anyway for preventative maintenance.

But concerning your thermostat, does the car warm up to just over the second (from bottom) white line and stabilize for a bit before increasing in temperature? This would be where the thermostat should open. If the temp just shoots straight up without stopping there, the thermostat may be opening late or it's flow is restricted. I'd doublecheck that you have the proper rated thermostat (if you don't remember and bought it mail order, have them check their records).

I'm also replacing the relay since mine is suspect. Not cheap at $111 (Pelican was the cheapest I found yesterday) but less than a head gasket.

Is the exhaust restricted in anyway? You'd probably have driveability issues as well with a clogged catalytic or collapsed downpipe. Let us know what you find...

 

Flight,

Thanks for the post.

Yes, the gauge does stabilize just above the first has mark for a while, then climbs after a few minutes.

I have an 83 degree Wahler therostat installed, which is the stock temp. I put it in a pot of boiling water last night, and confirmed it opens when hot.

I have not cleaned the ground wires, but believe the gauge is accurate since it reads just at about the 83 degree mark when the t-stat first opens.

I have ruled out the need for a relay (in my mind anyway) because I pulled the plug off the thermoswitch and got the fans to run at both temps by bridging the connections as per Clark's 944 garage. I even ran the car around with the fans bridged on high, and it still ran hot -- never over the top white mark, but right at it with the fans on high in traffic.

Someone suggested I look at my A/C condenser, to see if it is blocking the path of air. It definitely looks 17 years old, but I can still shine light through it. Since my a/c is discharged right now, I may pull off the condenser to see if that does anything.

I grabbed the pulley of the pump last night, and could feel very very slight play in the bearings.

I've been driving without the underbelly pan. Could that make such a big diff?

 

A good idea for these cars would be a thicker rad, meaning more water capacity to cool things down.

Has anybody tried a 160 degrees thermostat to see if that would cool things down?

Also i read on other thread about changing the impeller on the water pump. Give powerhouse a call i think they have some think for our water pumps.

 

Just a passing note regarding the boiling water. I too live in Florida. I've checked my bad water thermostat by putting it in water and it opened. Currently, I am replacing it every two years along with the belts.

When it starts going bad its stars by raising the temperature while at a light then the temperature starts going down after I start driving. The second stage is that Baby will start spitting coolant at me. The final and most dangerous stage is that she will overheat with the fans not even turning on (happens really quickly after start-up)

In my determination this is a dangerous situation and i stop driving my car until the issue is solved. Generally, I avoid using Vertex in Miami for part due to their higher cost except when it comes to the cooling system. There is a cooler temperature's switch that makes the fans come on sooner. I too did the water wetter route and pulled my radiator out to get it cleaned.

I have never experienced a collapsed pipe nor bad cat with this car. ed

 

I changed out the thermostat when I replaced the radiator. It's just a few months old. I have had the lower temp thermoswitch for years, but it runs hot even with the fans wired to run on high at all times. I forgot to mention that I have a test pipe, so a clogged cat is not possible.

Vertex is convenient for me, and I have not noticed their prices to be higher. You have to be careful who you deal with, and check that you got the right part if you don't get one of the knowledgable guys. Ian at 944online is close too, with solid knowledge and great service.

 

Here is an update on my car:

After checking everything I could think of, I decided to try the car without a therostate today. Guess what? It runs cool as a cucumber without the (functional) thermostat. In fact, I beat the snot out of it in 80+ degree weather and could not get the temp gauge to go over the first white line. At idle (with the fans bridged on high still), the temp falls below the first whire line. On the highway, it runs just below the first line.

So now what? I tried two new thermostats (both of which opened in boiling water), so I know the problem was not caused by a bad t-stat. Why would my car run so hot with a funcational t-stat, but run so cool without the t-stat?

 

My car runs at the low white line when moving. Then at the top white line in SoCal summer, stop and go traffic. The fans come on and that cools to the first white line. Does this mean my car is running hot too? I have Water Wetter, 15% coolant, the rest distilled H20.

Live to drive!

 

Tom,

Since you're using the correct thermostat, I think your problem is running without the belly pan. This made a huge difference on my car. In fact, I removed my aftermarket splitter (GT Racing type) too while running my problem down.

The factory definitely used the undertray to direct flow through the radiator and the condenser.

Once I put the undertray back to stock, my temps went back to normal even after installing an additional oil cooler in front of the radiator.