So, I replaced my rad cap and thermostat a few weeks ago and it seemed to cure an overheating issue but it has come back.

The issue is: Upon cold start up, the car will rise to operating temp and then overheat. The heater is cold at that point so there's no way the thermostat is opening. Once the thermostat does open, it's fine. No issues what so ever. And as long as the temp doesn't drop below 110 or so while the car is off, it wouldn't give me problems. The radiator was full and the system was blead.

I replaced the thermostat again last night and blead the coolant system. When I did this the coolant was still slightly warm. I tested it out by idling the car and the thermostat opened no problem.

This morning the temp raised up past 200 and kept going. I turned off my car and parked it facing down hill, tried to bleed the system more and after a few mins the thermostat finally opened.

Now keeping in mind, new thermostat, rad cap, full rad, and as far as I know blead system, what could the issue be??

I'm thinking maybe it has something to do with the mix. I'm honestly not sure if I have too much water in there. Suppose I do, the boiling point is too low, and it could be boiling and making air before the thermostat opens?

Any other ideas?

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

The heater being cold tells me you have air trapped in the system. The heater should warm up before anything else. I also noticed was you said you parked it facing downhill when you bled it. You actually want to park it facing uphill making the front of the car higher than the rear. You could also try drilling a small (1/16th) hole in the thermostat to allow it to self bleed a little.

Well, I let it sit for over 8 hours while I was at work. When I started it and let it get up to operating temperature, it did not overheat this time. I tried bleeding it a couple times anyway and no air came out.

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

95naSTA
just curies what brand and part number are the cap and thermostat?

I've got a 195* Stant Termo and I'm not positive but I think the rad cap is a stant also.

There has to be air trapped in the system. I watched the thermostat rise and lower hovering around 200* on the highway.

I'll try and bleed the system again tomorrow with the front of the car on an incline.

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

I'm pretty sure I found the issue.

I pinched the overflow tube with the battery last time I had it out.

I just let it get up to operating temp and bled the system. It did not overheat.

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

I just went out and drove the car to make sure it didn't overheat and it did. It did the same exact thing.

Any other ideas?

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

Mike are you using or loosing any coolant?

As well is the water pump a new part or an original?

Something isn't right.. Gotta hate when the car gets picky..

I'm not getting any puddles that's for sure. The area under the coolant elbow is a little moist though. I watched this area while the car was getting up to temp and there was no leaking.

The water pump is electric. If there was an issue with it would think the symptoms would be different?

How about a blockage somewhere maybe?

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

I am almost in the frame of mind that you might be having issues with the pump....

What Radiator do you have in the car?

It's the stock 227k old rad that came in the car. (Series 1 L67 originally)

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

I am not sure where you would have a clog... I think you may be having issues with flow.. Not sure why tho.. Has anyone ever heard of the electric water pump failing?

I agree with Don. Make sure you have power to the water pump while it is running.

I just made a post over on CGP to see how long other's electric pumps have lasted.

It's definitely getting power. Otherwise I would be having issues in the rush hour traffic I see everyday.

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

So, from what I am gathering here,

1. cold start - car overheats - what temp are you seeing?
2. warm start car is fine - what temp is the car at when started?
3. Car is fine in stop and go traffic

In original post, you mention an overheating issue you thought you fixed with a new cap and thermostat. What was the original issue?

240-250* High enough to set the 'check gauges' light.



If it's around 120 or higher.



Yes. Once the temperature finally drops the first time, and I get heat, the temperature does not get above 200*.



The original issue had the same symptoms but the radiator would be noticeably lower when the engine cooled and I would have to add fluid. A new radiator cap solved the issue for a couple weeks.

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

Have you done the UIM replacement yet? I am wondering if you are losing coolant through the EGR port? That is where my 95 was getting ready to leak from when we replaced it at 120k miles. The wall was really thin there.

My coolant ports are blocked off at the LIM and I opened up the wall behind the LIM access plate to make up for obstruction of flow.

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

Which coolant ports are blocked off? When was the intake work done (how long ago)?

I am still with Don and think you need to check out your pump. Is the coolant still ending up low after you drive it?

The TB coolant ports are blocked by my HVII. I ported the LIM 5 years ago.

The coolant level doesn't change after driving it now.

_________________

95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.