Hi all,
a couple days ago my 2000 Coupe started to suddenly overheat.
I've looked through hundred of archive threads but couldn't find a good match for my case.
Here is the quick story:
- Car started to overheat (260F) withing 0.5 Mile from cold start, Radiator was cold, no leaks or coolant loss, no heat inside the car
- Its not the sensor, its actually boiling
- Coolant is clear and clean, no froth or anything like that
- I replaced the T-stat (checked both new and old in water boiler, both were working)
- with new T-stat still overheating
- reservoir cap seems to be tight but have no way of checking the psi rating.
- checked for combustion gases in coolant with block tester fluid (loaner tool) but turned out negative (no exhaust in coolant)
- removed T- stat, checked & removed waterpump and checked radiator
- checked and opened stock waterpump (has no bearing play and impeller is still attached to shaft and turns freely, it also pumps out fluid but can't judge if this is the right amount)
- removed both radiator hoses and blew through them - no resistance felt so I assume its good.
- Put everything back together with the suspicion that I have a major air bubble in the engine. Left out t-stat.
- jacked up the front of the car and cracked the front coolant crossover connections to purge air. Filled radiator through top hose and topped off through reservoir.
- still overheats (240F) but much slower, now I have heat in the car again, radiator still not fully warm but better than before

I've had that cooling system apart probably 6 times in the past and never had an issue like that.

Please help me since I can't find the issue.
Can the pump lose output volume after 12 years of use? Is there a better way to check the radiator, could the headgasket still be faulty but without losing coolant or pumping exhaust gases into the water jackets?

Thanks so much,
Alex

 

Have you checked to see if there is debris, like a plastic bag sucked up in front of the radiator?

 

Yes, everything is clear, the radiator is free of debris and both fans work perfect (also come on at the right temp).

 

It's very unlikely for the water pump to lose output efficiency, unless the impeller vanes are severely eroded away. The shaft seal and bearing will usually be the first things that fail in a water pump.

The best way to check the radiator is to have it flow tested by a competent radiator repair shop.

A blown head gasket, from a cylinder to a coolant passage, will always be detectable by the method that you used.

Is your belt slipping on the water pump pulley?

 

I used this, worked like a champ awhile back. I suggest you try this. If not do a leak down and pressurise the system

 

Hi guys,
I did another test tonight which was much better than before but ended in 240F coolant as well after 20min of idling.
I cracked the crossover connection open again and was able to fill another 3 quarts into the system. Then I closed them and started the engine.
Still without thermostat it took a while to warm and it settled around 190-210 but after 15min or so it started to creep up to 240 where I shut it down.

I own this care since 2007 and have never had a cooling issue and I didn't pay much attention to the system and bleeding air whenever I took the car apart (3 cams, heads etc.). I have a hard time believing that suddenly an air bubble went into the engine that can''t be easily removed. Before, my car never went over 210 and stayed usually at 195 or so.
I'll try to drive it tomorrow and see if I can get to a repair shop for a radiator test. Is that done in the car and how much does it cost usually?
Thanks
Alex

 

My vote is air in the system. I had to use a vacuum filler to get all the air out.

 

Another note, after waiting a couple minutes after the last shutdown I checked the temperature of the radiator. The plastic endtanks were very hot still but the core was hardly handwarm. I then pulled the upper radiator hose from the water pump and blew through it. Immediately, coolant rushed out of the open pump port meaning that the radiator is not completely blocked
I have the feeling that the radiator's cooling capacity might be reduced.
Do the radiator flush products really work or are they just snake oil?
Thanks
Alex

 

did you change anything at all before this happened?

Is your tensioner pulley possibly failing?

Belt slipping on the water pump due to a lack of tension?

Attempt to spray out your radiator fins?

 

One week before the overheating happened I changed out my torque converter but in that process I did not open or disturb the cooling system.
The belt is not slipping as far as I can tell (no noise as well) and the pulleys were replaced 1 year ago and still seem to be in good shape. The radiator core and the AC condenser core were cleaned a while back.

 

Maybe you should get your system pressurised or the radiator itself tested.

 

and get the radiator cap pressure-checked as well. New replacement caps are now 18 psi vs the OEM 15 psi.

 

I believe you can rent them from autozone or places like that for free. Any pinholes in the system will cause issues.

 

I hit a road gator and bent the metal support for the center air deflector under the radiator. Coolant temp went up 50 degrees from normal operating temp (198) in about a minute. I looked at that darn thing twice and didn't notice it was tweaked until I raised the car off the ground. Pulled it off, straightened, and reinstalled.

HTHY

 

Where is the radiator cap?

I do not have one on my 2000 or really over looked it when i removed the radiator shroud cover.

I had a problem after replacing cooling hoses and water pump. I would hit 230 when driving under 35. I found a number of issues that needed attention.

My air deflector was out of position like it should have been

I started squeezing upper and lower hoses 20-40 times each after each time i would park and release pressure from the over flow tank.

I found that my upper radiator hose was twisted a bit causing fluid to travel up a hill. I loosened by an twisted the hose at the upper radiator connection lower the hose under the power steering fluid box. The fluid now has a downward flow.

I also found that the foam surrounding the radiator shroud had moved possibly causing air flow pressure to not flow across the radiator escaping out of the crack caused by the misaligned foam.

I also added two bottles of redline water wetter. Back at 200-205 now.

 

Yesterday I flushed the radiator with radiator cleaner. I disconnected both hoses, plugged the lower one and added the solution with boiling water. This time the radiator was hot across the whole core so I assume that the passages are indeed not blocked.
I also bought a new overflow tank cap, just in case. After the flush I reconnected everything, put the t-stat back in and refilled/burped the system as I did before. I'll test drive tonight to see what happens.
Thanks Alex

 

What does this mean exactly? Are you following the service manual procedure?

 

 

Statements in posts #1 and #7 indicate that the OP is attempting to purge the air by cracking open the coolant crossover flanges.

The procedure outlined in the service manual has always worked for me.

 

Hi all,

It seems that the problem is resolved and has magically disappeared!
After my radiator flush and radiator cap change yesterday I took it for a quick test drive which was successful. After that I put the radiator cover back on and went on a 20mile drive to a customer location with the temps hovering between 187 and 190 degree. Only when standing they rose a little (205 was the max I saw).
Incredible.
It seems that my issue was probably really only some air in the system and possibly a tired overflow tank cap for $5.
What I found interesting is that extended idling is not a good representation for the performance of the system since the lack of fresh airflow is making the temps rise so much faster.
I'll monitor it for the next days though.

Thanks again for your help,
Alex