Overheating Head Scratcher - fan clutch?

Maintenance/Repairs
1

Driving a 2004 Chevy Express van w/ Vortec 6.0 V8.

A while ago, the car overheated on me after the heat was blowing cold. Swapped the thermostat to no avail, had a mechanic look at it to confirm my hypothesis of shot water pump; he said that was probably correct (no coolant flow).

I swapped out the water pump, hoses, therm, coolant

Likely importantly, I didn’t replace the fan clutch. I’m new to this stuff and didn’t realize that was part of the deal.

For about a thousand miles after this, everything seemed to be working fine, if running slightly over the usual operating temperature - I just figured my new thermostat opened a little later than the original.

Recently, my overheating problem has come back. The heat will blow cold most of the time and not seem to be cooling. Periodically, whatever is not engaging engages; then, the heat comes on and the engine temperature drops.

Does an old fan clutch sound like it might be the problem? The puzzling part has been that it seemed okay for a while and then kept giving me trouble. Any chance that could be consistent with this sort of thing?

If so, is it likely that I ruined the new water pump? Should I replace this again?

The clutch and the radiator are practically the only cooling components that haven’t been replaced.

My radiator is also slightly bowed (was in a fender bender, didn’t think much of it), but doesn’t leak or anything. Likely that that’s be an issue?

Thanks very much, everyone!!

2
  1. Are you losing coolant?
  2. Under what conditions does the overheating occur?
  3. Is the radiator the original?
  4. Has all the air been purged from the cooling system?
3

I don’t think the fan clutch would affect the heater. It wouldn’t cause the engine to overheat either, except when driving at slow speeds or idling. You haven’t damaged the new water pump. I think you must either have air in the cooling system, a leak in the cooling system, a blocked / gunked up radiator, or maybe all 3. First step would be to check for any coolant leaks. I suspect that radiator might be leaking if it was hit hard enough to get warped.

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4

remove the radiator and take it to a radiator shop where they’ll give it a flow test.

Speaking of radiators, I was listening to Car Talk on my podcast device the other day and a caller said they had replaced their “raaaaadiator”. by this I mean they pronounced the “a” in radiator the same way you’d pronounce the “a” it the word bat. I’ve always pronounced it with the long “a” sound like in the work “ray”. Is this bat “a” sound a common way to pronounce radiator in some parts of the usa?

5

People who say r-ah-diator also probably say al-u-minnium r-ah-diator.

1 Like
6

Just found the following in making sure I was purging air properly:

“Following a condition where the engine coolant has been drained, if engine coolant is only added through the radiator neck and overflow res, the engine coolant may not flow beyond the closed thermostat located on the engine at the lower radiator hose connection. Though the engine coolant may appear full in the radiator neck, the system may be low, and a major engine overheat condition may occur”

This is… sounding very familiar.

Thanks all!

7

whenever I refill the radiator after draining it out for some reason I do it while the engine idles, and fill it a little at a time as the thermostat gradually opens. I don’t think any experienced mechanics would just fill a cold radiator from empty, put the cap on, and consider the job done.

8

Intermittent heater operation is usually due to a low coolant level, have you verified that the radiator is still full?

1 Like
9

In the Buffalo area the long A is usual, I have heard the short A, but it has always seemed like an affectation.

10

They use the long “a” (Ray-) version in New Zealand and Thailand as I recall from prior visits there. The Oxford English dictionary suggests the long “a” form in both UK and American English. The only reference I could find by Googling for the short “a” form is northern New Jersey.

11

A bad mechanical fan clutch, if that is what you have, will usually make a roaring sound and also will have a lot of resistance when you turn it by hand. I’m thinking maybe a restricted radiator. They’re pretty cheap now and do get gummed up over time. I hate to say it but that also could be caused by a head gasket that will act like low coolant.

Yeah I was listening to a youtube from a guy from Australia and he pronounced aluminum like that. Had to play it over a couple times just to figure out how they could mangle it that bad.

12

That word is spelled differently in the UK vs USA. It’s spelling changed 3 times in the first 5 years after its discovery. The USA uses the second spelling, and the UK the third (aluminium).

13

If everything else is operating as designed the fan can be removed and the engine will not overheat if driven 45+ mph. It does sound like there is a problem with too little coolant which could be the result of a head gasket problem or failure to properly fill the system but the fan and clutch are likely not the cause. I’ll be scratching my head while waiting for the solution.