Resolved Grand daughters 2003 3.8 v6 overheating

Rck · Sep 28, 2023

She ran it until head gasket blew. Took heads out and had them planed and cleaned.
All new gaskets. Replaced thermostat, radiator cap and water pump since car has 159,000 on it.
After running for 20 minutes, slowly overheats. Water moving fine in radiator. Bled all air. Antifreeze looks clean. Help!!

Noobz347 · Sep 28, 2023

Can you see any [scale] built up inside the radiator?

How does the fan and shroud look? Is it moving a lot of air?

Have you washed out the fins on the radiator? -- Cold engine, foaming degreaser, garden hose and nozzle, rinsed from back to front.

Since the heads were done, have you noticed any coolant loss?

Rck · Sep 28, 2023

No scale. Rad is clean
Fan runs as it should and moves air Shroud is good.

Noobz347 said:
Can you see any [scale] built up inside the radiator?

How does the fan and shroud look? Is it moving a lot of air?

Have you washed out the fins on the radiator? -- Cold engine, foaming degreaser, garden hose and nozzle, rinsed from back to front.

Since the heads were done, have you noticed any coolant loss?

Rck · Sep 28, 2023

Rad is clean. Fan and shroud. Are good. Have not cleaned outside of rad.

I have tape on overflow and no antifreeze loss.

Rck · Sep 30, 2023

Rck said:
Rad is clean. Fan and shroud. Are good. Have not cleaned outside of rad.

I have tape on overflow and no antifreeze loss.

Cleaned radiator. No change but thank you for suggestion.
Im wondering about removing thermostat and trying it

Rck · Sep 30, 2023

Going to try to run with no thermostat. May advanced sold wrong one. Has happened before

Noobz347 · Sep 30, 2023

Rck said:
Going to try to run with no thermostat. May advanced sold wrong one. Has happened before

Easy enough to drop the t-stat into a pot of boiling water to see if it's working.

I wouldn't run the car long without the t-stat though. The EEC will [not] be happy.

Rck · Oct 1, 2023

Thats next.

Rck · Oct 4, 2023

After car overheats, I crack open rad cap, send some fluid to overflow, tighten cap, start car and temp is normal.
Antifreeze I catch that dribbles out is warm to the touch but not as hot as upper hose.

Mustang5L5 · Oct 4, 2023

Have you done a cooling system pressure test and tested the radiator cap?

Rck · Oct 5, 2023

I will try that next.

Rck · Oct 5, 2023

Question on pressure test.
When car shows overheated, I loosen radiator cap and it blows antifreeze, no air bubbles, into overflow? After an hour, antifreeze level in overflow is back to normal. Also, after removing pressure on system, I restart car and have normal temp reading for 10 minutes or so.

Mustang5L5 · Oct 5, 2023

That's typical. Doesn't really tell us much. Sounds normal, so likely a pressure test will come back good, but it's one thing to check off the list as confirmed good. AUto parts stores typically rent these units, so it's easy enough to do.

Rck · Oct 5, 2023

Thank you

LILCBRA · Oct 5, 2023

Looking past the obvious things in the cooling system - have you double checked and verified timing? If you removed the cam position sensor synchronizer (aka old school distributor) it's possible that it was reinstalled incorrectly and/or out of adjustment. Timing that is retarded too far will cause overheating yet it may seem to run correctly. I chased my tail over this very scenario one time - I swore the timing was set correctly until I put a timing light on it. The overheating issue ceased once timing was set correctly.

Another possible scenario could be a lean condition, but I'd guess that that's less likely.

Rck · Oct 5, 2023

I will do that next

Rck · Oct 5, 2023

No way to set timing on a 2003 3.8 v6. All is done by computer according to the book. No timing marks anyway.
Thank you for the response.

TIGGER · Oct 5, 2023

I assume the head gaskets blew due to overheating? When it overheats, is the AC on or does it overheat no matter what? Does the 03 have a CCRM? When you said the fan is good, does that mean it is on/running when the car is overheating?

My wife's 96 GT vert only overheated when the AC was on. AC off on a 100+ degree day was no problem. At first it only overheated it when you were running errands, shutting the car off and on. If you got in the car first thing in the morning, it stayed cool (with the AC on) just fine until you shut the car off for the first time . This went on for a couple years till a couple months ago when it overheated all the time with the AC on. Fan was working properly so I swapped the CCRM with a good used one I had. Problem solved.

Rck · Oct 5, 2023

Air is not on. Driving it over heats around 20 minutes. Sitting still in about 25. Just pull the pressure test and it held over 6 minutes.
No foam in oil or white smoke. Antifreeze level is constant. It pulls antifreeze in from overflow when cooled but wont push it in when hot. Changed rad cap. Cracking rad cap puts coolant at normal level in tank.

Rck · Oct 5, 2023

Mustang5L5 said:
That's typical. Doesn't really tell us much. Sounds normal, so likely a pressure test will come back good, but it's one thing to check off the list as confirmed good. AUto parts stores typically rent these units, so it's easy enough to do.

Just pulled pressure test at 16#. Held for 6 minutes. Instructions say hold for 2 but wanted to be sure.

Resolved Grand daughters 2003 3.8 v6 overheating

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