Engine overheating, need advice

[berickson926]

Car seems to want to overheat when backing into my driveway, or idling. Surface street driving on short trips the car seems to be okay.

DMC CA did a radiator flush about a month or so ago and I haven't seen coolant leaks anywhere on the car.

Once I back into my driveway the temp creeps up to 220 and if the fans do kick on its only for a few seconds. Once I turned the car off the overflow hose lets out a couple ounces of coolant.

I wasn't able to look at the car for several days but when I came back to it, the overflow tank was basically completely full. I was expecting to top off what was let out previously.

I took it out on another short drive to see how stable the engine temp is. After about a fifteen minute drive the car seemed to be alright until I got back to the driveway. Once parked it was sitting at 220 and letting out coolant from the overflow tank again after I shut it off.

I don't have tools to accurately pressure test beyond just squeezing flexible hoses by hand at the moment, or an infrared gun to check specific temps. Sorry.

Just by touch I observed a couple of things when I let the car idle in the driveway while warm:

-Driver's side pipe (105988) just before radiator is very hot, but passenger side pipe (105992) is almost room temperature.
-Water pump hose LH (108675) side was very hot and had comparatively good pressure, water pump hose RH 108676 was colder and the hose seemed to have lower pressure than the LH.
-Radiator fans kicked on but only stayed on for a short time. Maybe ten seconds or so and definitely not long enough to keep things below 220.

Any troubleshooting advice would be appreciated!

Seems odd that there is air in the radiator after having it flushed so recently.

Thanks!

[AugustneverEnds]

Sorry to hear about your troubles!

Your cooling fans are definitely not working like they should be. I would check the circuit breaker first. It should be upgraded to 40 amp. From what you describe the fans click on (indicating the otterstat is working) and then the circuit breaker opens and turns the fans off.

[Josh]

Sounds like the thermostat is failed closed. I would replace it and make sure the system is properly beld. If the fans aren't turning on that could be another separate issue. They should turn on somewhere in the 205-210F range and shut off somewhere in the 190s

[David T]

Sounds like the thermostat is failed closed. I would replace it and make sure the system is properly beld. If the fans aren't turning on that could be another separate issue. They should turn on somewhere in the 205-210F range and shut off somewhere in the 190s

The round tank on the right side of the engine bay is NOT an overflow tank. It is a header tank and when cold should be 1/2 full. My guess (and it is only a guess because you didn't provide enough information) is that you need to replace the otterstadt switch and the cooling fan circuit breaker. If you still have the fan fail relay it should be removed and replaced with either the bypass or an upgraded relay like a Mr Cool or a Fanzilla. You should also check that both fans run when the fans come on and that the fans on both motors are securely attached to their shafts. Since you say the car is OK when moving it would point to a problem with the cooling fans which keep the car from overheating when the car is not moving.

[hmcelraft]

Take it back to DMC CA - They need to get the rest of the air out of it. It sounds like there is a lot since the fluid appears to stop moving at low RPM - based on your comments.

[sdg3205]

Agreed - Sounds like air in the system.

Do yourself a favour and buy Toby's complete self bleeding kit. Makes bleeding a breeze.

[Jonathan]

Is your driveway flat or on an angle?

[David T]

Is your driveway flat or on an angle?


No, No, No. If the car's cooling system can keep the motor from overheating under load while moving then everything would seem to be OK EXCEPT the cooling fans whose only purpose is to keep the car from overheating when the car is NOT moving or moving slow. What has to be done is to find and fix the reason the fans aren't coming on when they should and why they don't run long enough to keep the motor cool.

[berickson926]

Thank you for the advice, everyone!

I had taken a quick look in the fuse box but only to see if anything looked melted (there wasn't anything). I will take a closer look regarding the 40amp breaker for the fan circuit and relays.

The driveway itself is basically level but I don't have a self-bleeder kit installed. It was on my to-do list but sounds like something I need to tackle to rule out issues with air in the system.


It sounds like if I can rule out electrical/fan/otterstat and air issues, I should move on to the thermostat.


Also, apologies on the referring to the header tank as overflow. Whoops!

[berickson926]

Going by this diagram (http://i.imgur.com/4FvQG.jpg) the circuit breaker in the cooling fan slot (#20) appears to be rated at 40A and the one adjacent to it is 25A. I'm not sure if these are wired up backwards as it seems like the 25A breaker has four wires connected to it? I want to go back out to the car and double check this again.

The fan fail relay had already been replaced with possibly the bypass David T. was referring to. I think Bosch relay in the cooling fan slot is considered updated but I'm not really sure about that either.

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[kings1527]

There are only a few *basic* things that can cause your car to overheat:

1) air in the system
2) no coolant in the system (not the case here)
3) bad otterstat
4) bad fan fail relay
5) bad cooling fan relay (located just to the right of the fan fail relay slot)

The cooling circuit is pretty simple. I'd second the recommendation of getting Toby's bleeder kit. That makes life extremely easy for bleeding the system. If yours haven't been changed in awhile, I'd get a new otterstat for $20, a new fan relay, and bleed the system again. One of those things is probably the cause. I like having solid parts in the car's cooling system. I swapped all of that out about 2 years ago and my car has never been close to overheating and has performed within spec perfectly. I'd also recommend looking into a fan sequencer from Julee and Dave. That'll take up the fan fail and fan relay slots and solve that issue immediately. Otterstats are easy to replace and cheap, too.

You do NOT want to overheat this aluminum engine. If you don't overheat it and you do regular oil changes, it should last several hundred thousand miles. The lubrication within this engine is outstanding and the engine overall is very stout.

[kings1527]

And add in a 'bad thermostat' to my list above...

But I'd try the others first. Easier to do!

[hmcelraft]

I still suspect you have trapped air in the cooling system. I am assuming the system was working fine before the coolant change and flush? Your narrative suggest to me that the engine temp rises rapidly as you park the car which, it should not and, is an air-in-the-system symptom.

In your pictures it appears to me that you have a circuit breaker AND fuses for the fans. Redundant - you don't need both. I personally prefer a 15 amp HD circuit breaker for each fan but, there are various working setups. Also, the wire at your CB connection looks damaged - damaged enough to create heat at the CB which could cause cycling of the CB and premature fan shut-down. That connection needs repaired.

[AugustneverEnds]

I still suspect you have trapped air in the cooling system. I am assuming the system was working fine before the coolant change and flush? Your narrative suggest to me that the engine temp rises rapidly as you park the car which, it should not and, is an air-in-the-system symptom.

In your pictures it appears to me that you have a circuit breaker AND fuses for the fans. Redundant - you don't need both. I personally prefer a 15 amp HD circuit breaker for each fan but, there are various working setups. Also, the wire at your CB connection looks damaged - damaged enough to create heat at the CB which could cause cycling of the CB and premature fan shut-down. That connection needs repaired.

Good catch!! The brown/orange wire is almost broken off. Just cut off the connector and crimp on a new one and see if that fixes the issue with the fan.

[berickson926]

Thanks for the advice and feedback everyone!

Well I went through all the electrical bits, ruled out bad relays, checked fuses, replaced the circuit breaker & connection repaired, new otterstat.

Tried my hand at bleeding the system myself but some old hoses were bringing air into the system (I don't have a pressure tester). I ended up having DMC CA help me troubleshoot and replace since I still couldn't figure it out.

My radiator is clogged too so that will be the next thing to tackle. At least I was able to drive the car home without issues.


Looking at things in a positive light, at least I learned a bit more about the car!

[AugustneverEnds]

Thanks for the advice and feedback everyone!

Well I went through all the electrical bits, ruled out bad relays, checked fuses, replaced the circuit breaker & connection repaired, new otterstat.

Tried my hand at bleeding the system myself but some old hoses were bringing air into the system (I don't have a pressure tester). I ended up having DMC CA help me troubleshoot and replace since I still couldn't figure it out.

My radiator is clogged too so that will be the next thing to tackle. At least I was able to drive the car home without issues.


Looking at things in a positive light, at least I learned a bit more about the car!

Autozone will loan you a pressure tester free of charge. The adapter fits the overflow tank perfectly. Just ask for it, you put an $80 deposit down which is refunded when you return the tester.

Sorry I forgot to mention that earlier!

[David T]

Thanks for the advice and feedback everyone!

Well I went through all the electrical bits, ruled out bad relays, checked fuses, replaced the circuit breaker & connection repaired, new otterstat.

Tried my hand at bleeding the system myself but some old hoses were bringing air into the system (I don't have a pressure tester). I ended up having DMC CA help me troubleshoot and replace since I still couldn't figure it out.

My radiator is clogged too so that will be the next thing to tackle. At least I was able to drive the car home without issues.


Looking at things in a positive light, at least I learned a bit more about the car!

Now you're saying the radiator is clogged but in your first post you said DMCH-CA flushed it out. Did it get plugged up since then? If the car doesn't overheat while you are driving it over 30 MPH the radiator is working. You should be concentrating on figuring out why the cooling fans come on at too high a temperature and why they won't stay on till the temperature drops. You probably need a new Otterstadt switch and circuit breaker at least.