OVERHEATED 328

Fast temp fluctuations sounds like the thermostat getting sticky and then stuck closed. Is that easy to replace in your car? Mine is $6 from Pep Boys and replaces in 10 minutes so it's easier than tearing into other stuff first. YMMV.

Ken

 

Mark -- Could you be a little more vague?

What choice do you have but to: 1) refill the system and confirm/bleed at the radiator and thermostat housing (heater valves "on"/"open") and then 2) run the engine (stationary) until:

1. the fans come "on", as expected, and everything's fine,

2. the fans don't come "on" and the indicated temp continues to climb to ~200 deg F (and you shutoff the engine), or

3. the fans come "on" at a reasonable indicated temp, but the indicated temp still continues to climb to ~200 deg F (where you shutoff the engine).

Can you be more specific about the symptom?

 

Odds on its your expansion tank cap

What happens is the spring gets weak & so as you drive along water escapes from the overflow - which of course you don't see happening.

Eventually your cooling system gets low enough that you start seeing the symptoms you describe - the temp sender is in the V of the engine & so if the water is very low the sender is dry & the gauge starts reading all over the place. Blip the throttle & the waterpump sends a gush of water through that makes the thing read straight again - temporarily

Get yourself a new 1.1 bar cap & all should be well. The Ferrari caps are crap & don't last. Unfortunately they are the only square ones that look right. I'm on my 3rd in 6 years.

If you want to test that this is the problem then refill the cooling system & bleed it from the radiator and the T'stat housing. Then button it up & either let the thing stand at idle till you get operating temperature & then rev it a bit - or just take it for a run. Immediately after you shut it down I bet you'll see coolant on the floor under the expansion tank.

Alternatively many garages have expansion tank cap testers. My last one was chucking out coolant all over the shop & when tested would barely hold 0.7 bar.

The original caps were 0.9bar but were superceded with (and you should be sure to get) a 1.1 bar cap

If you have a properly functioning system your gauge should read to about the second mark & should be pretty much stable in all driving conditions unless you get into traffic where it will climb to the middle mark 195F/90C. At this point the fans should cut in. If your gauge moves around a lot while driving & drops below the second mark on the freeway the odds are your thermostat needs replacing.

Good luck, let us know how you get on.

I.

 

I agree with Steve...make sure you bleed, bleed, bleed the system...trust me I know..& it takes time unless you have the tools so you can pull vacuum on the coolant system...

 

Bleeding the thing is all well & good but first he needs to find out why his system is so dry the thing is overheating.

Assuming he doesn't have a basic leak somewhere then it'll be the expansion cap & he will be by far the first to wonder why his car is overheating/temp gauge yo-yoing around & to then find the cap is at fault.

Its cheap to fix initially - but it won't be if he continually cooks the thing.

Change the cap, bleed the system and chances are all will be well.

I.

 

..air builds up from cavitation at the pump, IMO and any other pinhole leaks you may have...

The 1.1 bar cap is a must..

Sounds like you have a temp switch problem or a fan motor failing.....I've had them where you could jiggle the wire it'd run....turn your back it'd stop.....LOL!

 

I still have the 0.9 bar cap and made it through a deep summer south last year with it. Am I doomed? .

 

Air building up in the system is unlikely to cause the coolant loss unless he's got a major and visible leak somewhere.

The sensor for the temperature gauge is on the engine, the fan switch is on the radiator & the signals from either can be completely unrelated if the water levels are low. Low water levels can cause very high temps in the engine while the temp in the radiator is fine & not yet high enough to kick the fans in.

All the symptoms he has stem from coolant loss and the most common cause of that is the cap. He needs to rule that in or out before he starts messing with the electrics or the Thermostat IMHO.

I. (who's been down this road before!)

 

No, just lucky......so far

 

Good stuff - looks like the rest of the system is OK. The question you now need to answer is why it was 2 gallons light. Either it was never filled properly in the first place or you have a leak. Another option could be that the cap you replaced was leaking & since you replaced it you already cured the problem.

Suggest you do as I said & look to see if the tank cap is holding pressure and then if it is you need to look elsewhere & find someone with a radiator pressure test kit. If you (and the car!) are anywhere near the South East of the UK then I've got one.

Also, on testing the fans, the thing you also need to test is the temperature controlled switch. Get the car warm & then let it stand at idle & watch the temp gauge. The fans should cut in at around 195F/90C. If they don't then either your gauge is off or the fan switch isn't working. An infrared thermometer should tell you which. The temp sender is located in the V of the engine & sometimes the contacts on that can get a bit scratchy - a clean up of those often fixes wandering temperature gauges.

I.

 

I'd still keep a very close eye on it for the next month or two & keep bleeding the system . Make sure your heaters are working - you may well get air trapped in there.

 

No trouble (we knew what you meant -- we've BTDTGTTS ), and glad you got it sorted out with minimal fuss.

You don't need to mess with the thermostat bleeding, but do some more rebleeding at the radiator to get a feel for how much/how quickly/if any air is returning and how often you need to check as Iain suggested (maybe check in a week, then monthly if OK after the week, and then quarterly if OK at the monthly check). Bleeding out a pint~quart of air at the radiator every 2~3 months and refilling the corresponding amount of coolant mix would be "normal-ish" and not a cause for great concern IMO (but it's definitely something that can't/shouldn't go unchecked for long peroids).

 

Two gallons of Prestone? Make sure you keep the dilution at a 50/50 level with water. Water seems to cool better than "coolant" so having a stronger dilution with Prestone is not necessarily a good thing. And may cause you to lose some cooling capability.

 

Glad to hear you're okay for now.

Cooling system should stay more or less full. If you are losing coolant (and not leaving a puddle) or frequently bleeding air out there could be a head gasket issue.