My FD keeps overheating
 

Well, after 5 years of (relatively) trouble-free almost daily driving, my FD has developed cooling issues. It started yesterday after some hard free-way driving. The temps were fine but after I parked the car, the fans came on and seemed to run harder than usual. I didn't think anything of it and got back on the freeway and drove hard again. After about 20 minutes, I exited and then noticed that the temps are slightly above the middle, and the coolant light came on.

Fortunately, I was near a Sears, so I parked the FD, and bought some coolant (50/50). I let the FD cool down, went to grab some lunch, and then came back and filled up the overflow tank (which was at the "L" level) and drove home...I forgot to check the level at the filler tube.

EVerything was fine for about 45 mintues during the drive home, but then the temp started going up again, and the coolant light came on on the freeway. By the time I pulled over, the temps were fluctuating and had gone almost as high as the the "red" marker before coming down. I realize that I should have pulled over right away but I was almost home.

After I parked the car and while I was waiting for it to cool down, I noticed some coolant coming out of the overflow tank. I checked the filler tube this time and had to add almost half a gallon of coolant before the level got up to the filler neck, I also noticed that the rubber seal on the filler cap was torn. The temps were OK during the short (5 minute) drive home.

I replaced the filler cap last night and added a bit more coolant. I took the FD out for a short test drive this afternoon (a little over an hour) and while the coolant light did not come on, the temps are still higher than normal. The symptoms are as follows:

1) Engine temp starts to go up after about 45 minutes of driving. The temp will climb, and then start to go down (I assume when the fans come on), and then go up and down in cycles.

2) The cycles start at slightly above normal (middle of my stock temp guage), go almost as high as the "H" mark, then down and then up again. The intervals are about 5 minutes.

3) No white smoke, no coolant smell in the exhaust during the initial cold start.

4) No bubbles in the filler neck after the initial cold start, but the coolant level does seem to fluctuate after the engine warms up.

5) Coolant level seems OK at the filler neck both before and after the drive, and as I stated earlier, the coolant light did not come on during the test drive.

6) I did not see any coolant on the ground below the overflow bottle after my test drive, but when I look at the bottle from the top, there appears to be some wetness at the base of the bottle's neck.

So, what do you folks think? It almost seems like the water pump is not cycling the coolant fast enough to keep up with the heat being generated, the engine heats up, the fans turn on, the engine cools, fans turn off, and the cycle starts over again. I suppose the initial coolant loss was due to the bad filler cap?

The pertinent info on my car is:

1994 R2

Pineapple rebuild (5 years old, about 60K miles), 3 mm, street port, their stage 1 oil mod, and their heavy duty water seals

Fluidyne radiator but stock AST (5 years old also)

DP

RB catback

Fighter's Garage Intake with heat shield

Greddy SMIC with Greddy elbow

99 twins, manual boost controller set to 12 psi

Pettit ECU

My apologies for the long post, but I assume you'd want the ugly details if you're going to help diagnose my car's issues. Thanks in advance for any insight you can provide.

If you hit the red on the stock gauge than there is a pretty good chance you've got a rebuild in the near future :(

Is the hole at the top of the wp cover "weeping"?

Sounds like a crack in a cast iron on the exhaust side. My engine had the same types of issues before I rebuilt it. There was a crack and the water jacket was burnt up near the track.

Thanks for the replies. My wallet is already bracing for the potential (OK probability) of a rebuild.

I still like to figure out what happened first. I've been doing some searching, would a sticking thermostat cause the temp fluctuations that I'm seeing?

Try replacing the t-stat and see.

i would also consider replacing the water thermosensor or check it's connection, sounds like the fans are relying on the auxiliary switch which is rather hot to pull temps back down.

have you checked to see if the fans turn on before the temp climbs above mid-way?

What's "higher than normal" temps?

All your symptoms sound like a bad pressure cap. Air prob got into the system and has not fully bled out. I would let the car cool completely, and then fill and fully bleed all the air out of the system (I swear by this: Lisle Spill-Free Coolant Funnels 24610 - SummitRacing.com).

Also, check for any small leaks that may be introducing air into the system.

Have you pressurized your coolant system with a tester? Test the system, it should not lose any pressure overnight.

If it looses pressure, check the obvious first. Hose clamps, O-rings, turbo gaskets, ect. If everything looks good, it may be time to tear it down. Much cheaper now, before all the internals are overheated...

Also to bleed the system on these engine you should really have something like this; I bought one and it is AMAZING!! Used it on every car I have owned and messed with since. No mess and you actually have a chance to get the system up to temp!

IMO an engine that goes into the OEM gauge red even once should not be driven until you pin point what is going on. Good luck!

Edit; moehler already beat me to the leslie funnel! Well played Sir, well played.

Just an update for those of you who are interested, I had my car towed to the trusted local rotary shop this morning. They checked for signs of permanent engine damage and they don't think I'll need a rebuild, so I dodged the bullet this time.

They are currently looking into the cause of the overheating and coolant loss.

To answer Moehler's question, I hit the red mark briefly when I was low on coolant. However, even after I filled the engine with coolant, the temp (stock) gauge would cycle from middle of the gauge to about the three-quarter mark and it would go up and down every 5 minutes or so. It only does the temp cycling thing after about 45 minutes of driving.

Radical, I have almost zero car repair skills and little time to learn them, so the local shop will look at the things you (and everyone else) have mentioned until they find the cause.

Thanks for your time everyone.

Good luck I hope everything turns out well .

Thanks Tem120, everything's fine now.

I got car back from the shop last Thursday, it was only the thermostat. They replaced it, and the car's been driving great since, I took a 4 hour drive yesterday and had no squawks. Temps are fine, coolant level is stable.

To summarize:

1) Bad filler cap seal caused coolant loss
2) Bad thermostat caused temp to go up above normal

Both were replaced and the car's running great. No signs of permanent engine damage.

Glad to hear. Air in system, thermostat and bad caps would have been my guesses. Happy it worked out and you were able to save some coin!