Engine never comes up to temperature

[Xnke]

Alright. So I have the 5 and 6 external water lines run along the cylinder heads; stock heater hose connections into the cabin; a 160F thermostat, and a stock 1972 radiator, that has been cleaned out and refurbished. New Atsugi water pump, and MS1E is reading a GM temp sensor in the stock sensor location.

 

In the summer time, the 160F thermostat will keep the engine around 180F, with no AC on, or 195F with the A/C on and the dual 12" fans running, get into traffic on a 100F degree day with the A/C on and you're pushing 210 degrees in two minutes.

 

Now that it's getting cold, I can't get the temp up over 150F in stop-and-go traffic, and on the highway at 65MPH it's running about 145F. I have a candle in a cavern for heat and defrost, and in the 20 minute drive to work, even with a 10 minute warmup I STILL never get out of warmup enrichment so the Z is drinking fuel like it's going out of style.

 

Anyone got any ideas? Radiator cover? Summer and Winter Thermostats?

[ozconnection]

How hot does it get with the 10 min warmup?

 

Dunno, things don't seem right, with a 160 thermostat and you're seeing 210 in summer, that seems too high too me with that temp. thermostat.

 

And now you struggle to get past 145 with colder weather.

 

The two don't add up but.....

 

Try putting in a new and tested 180 thermostat and report back.

[Xnke]

Ok, letting it sit in the driveway for half an episode of Topgear, and it warms up to 191F. As soon as I start driving, the temp starts falling, till about 145-150F. Even driving with the heater core turned off doesn't change anything...heater core turned off and driving still falls to 153F.

 

The thermostat isn't even opening up other than what the water pump is pushing open...and if the heater is on then there is a full 3/4" bypass around the thermostat.

[Xnke]

New 180* thermostat installed. as soon as the sealant cures up I'll top off the radiator and go for a drive.

[ozconnection]

Please report your findings with the 180 degree thermostat.

 

Your scenario is strange and I'm curious how this change effects things.

[AlexPie]

mine does the same thing it warms up nicely

 

but once I go for a drive above 60 mph the temp drops

 

then when I slow down its back up to normal temps.

 

Edited December 4, 2011 by AlexPie

[kiwi303]

maybe you need to cable tie some cardboard over the radiator so only 1/2 has air passage through during winter your cooling is TOO good.

[Tony D]

Several things:

Yes, summer and winter thermostat.

The temp should NOT go to 210 in Yhe summer if you have sufficient rejection on the radiator. If I can tow a trailer uphill with a three core at 85mph in 115-120F Palm Springs Desert Heat, and keep ROCK STEADY temps WITHOUT the 5/6 mod...you should have no issues at all! Remember the mod DECREASES the differential between front and back of the engine, it doesn't completely eliminate it. If you're 210 at the thermostat, you're 215-220 at Thr back of the head. That can still cause issues if you don't have at least a 16# radiator cap.

 

Did you route the 5/6 mod to be controlled by the thermostat, or put it to the upper portion of the thermostat, bypassing it? JeffP made his block for the wYet from that point to come either spot by changing the thermostat position-there was an issue when we didn't have them controlled by the thermostat.

 

This post would be a good addition to the sticky on the mod in the FAQ/Stickies forum.

[Tony D]

My stock 260ZT won't reach temp idling, period. I have to drive it to get a tempersture above around 150. Idling in the driveway with the Nissan CHT, it won't get Ho 160 unless I put some sort of load on the car. Drive half a mile down the road and I'm regulated nicely between 165-170.

 

But idling? Sits at 150-153 forever on am 80-05 degree day. Likely lower colder...

 

Heater on "Heat" with no fan will bump the nber somewhat.

 

That's reading it on the MS Datalogger and Megatune.

[strotter]

At this point, ignore the radiator. The coolant circuit out to the radiator should not even be a part of the calculation at temps less than the thermostat cut-off temperature. Confirm the function of the thermostat. ALSO, don't use a cheap auto-parts store thermostat. Pick one up at the dealer. You'd be amazed at how much of a difference such a seemingly simple thing can make. Looking at your numbers, I'd suggest you also carefully look at both your timing curves and your mixture situation. That motor is not behaving correctly, there's more than one thing wrong.

[Xnke]

well yeah...the thing is a pig to drive cold. It will warm up in the driveway to 190F now, sitting idling. the electric fans cut in at 180F radiator temp. Drive it around and it'll remain nicely regulated in town, although it was 70F out yesterday.

 

My buddy's essentially stock-plus-MS1e ZXT runs a rock-solid 164F all the time, unless we just get rough with it, say six or eight back to back full-sprint highway runs of three miles, playing around the ramps. Then the oil temps come up to about 270F and we back it down...water temp comes up to 175F. That's it. Ambient temp that day was 89F.

 

He also has heat at the vents...real heat...in two minutes of idling. Mine never gets as warm as his does in two minutes. Mine also never comes out of warmup mode and is just AWFUL on gas if I don't drive the piss out of it, given that the air temp is 40F or less. Again, yesterday it was 70 degrees and the car was absolutely a joy to drive.

 

I'll get some short datalogs of the (admittedly imperfect) tuning, right now is the time to work on warmups but I can't even get it fully warmed up, so it's not working out well.

 

Yes, the 5/6 water lines return to the lower thermostat housing, and are controlled by the thermostat. The heater core inlet is from the cylinder head, and it returns to the inlet of the water pump.

Edited December 5, 2011 by Xnke

[BLOZ UP]

Can I barge in here as well?

 

I just got my VG30 running in my 280Z. I have an ebay aluminium radiator (for a 280Z), and it's, say, +2psi cap. I'm using the stock VG thermostat, 170 degrees.

 

So, I just got to filling and testing the coolant pipes and cooling system, so I was trying to warm it up. I can't drive it at the moment, so it's sitting in my garage.

 

Keep in mind I'm reading temps from the CHTS, not water temp.

 

I started 31 degrees ©, and 22 minutes later (!) it just got to 86. So in other words, it took over 22 minutes (since I started warm already) to come up to temperature. The head should be at 190, at least, right?

 

So what gives? It never opened the cap; I found some leaks in the upper coolant pipe that I need to fix, so the pressure never got quite there.

 

I have the stock dash gauge hooked up to the VG30 sender, since the curves are the same. It slowly rose and stayed in the middle, for whatever that's worth.

[bjhines]

Honestly what you are describing sounds like a bad thermostat. It never quite closes and it never quite opens either. You can see that visually. Pull it out and I GUARANTEE that it is cracked open when cold. Toss it in near-boiling water and it should open >1/2" in 5-10 seconds.

[BLOZ UP]

Nah, it's a new thermostat. I just think once it opens the radiator has much more capacity than the Z31 radiator, so it takes forever. I'll have to see how it does during an actual drive. I may need a bigger intercooler and A/C condensor...

[NewZed]

The thermostat's main function is to keep coolant in the engine until it reaches a certain temperature. If the thermostat's working right, you must have a lot of coolant bypassing it.

 

Edited.

Edited December 13, 2011 by NewZed

[bjhines]

The thermostat will allow the engine to come up to temp REGARDLESS of how big your radiator is. You could plumb a nuclear power plant cooling tower into your system and the god-damn water will not cycle until the WATER IN THE BLOCK gets hot enough.!

 

I notice you have been chasing leaks and put a low pressure cap on the radiator(bad idea for a turbo!!!!)... Are you sure you have enough water in the engine to contact the temp sender and thermostat.

 

I hate these discussions where the poster will not do the most basic fact finding tests that any competent mechanic would do the first time. There is absolutely no mystery to this. Fix the glaring problems with your cooling system and it will work fine.

Edited December 13, 2011 by bjhines

[BLOZ UP]

The thermostat will allow the engine to come up to temp REGARDLESS of how big your radiator is. You could plumb a nuclear power plant cooling tower into your system and the god-damn water will not cycle until the WATER IN THE BLOCK gets hot enough.!

 

Right. The engine I suppose comes up in the operating range, 70C. But that's the low end of the range, and it just sits there, because that's when the thermostat is fully open. Relax, it's just water.

 

I notice you have been chasing leaks and put a low pressure cap on the radiator(bad idea for a turbo!!!!)... Are you sure you have enough water in the engine to contact the temp sender and thermostat.

 

Right, have been, as in no longer. I put a lower pressure cap in, as in lower than what came with the radiator, as I saw no need to have a 20 lb. cap. Now it's back at the original 13 lb cap. Although, it was nice to "stress test" the cooling system to find the leaks. If I find that cooling this motor is so difficult that a higher pressure cap is needed, then I'll worry about it.

 

Yes, it has enough water.

 

I guess my turbo is going to explode now that the cooling system is completely insufficient with this cap and you know, within OE (VG) specs.

 

I hate these discussions where the poster will not do the most basic fact finding tests that any competent mechanic would do the first time. There is absolutely no mystery to this. Fix the glaring problems with your cooling system and it will work fine.

Me too, but I hate the ones were people just make broad assumptions about me even though I just swapped, fabricated, wired, programmed, and soon enough, tuned an entire engine swap. I just don't understand these darn cooling systems!

 

What is glaring is that everything is working fine; the S30 cooling components are more than adequate for the VG30. I need more antifreeze and less water in the coolant.

[NewZed]

 

"Nah, it's a new thermostat. I just think once it opens the radiator has much more capacity than the Z31 radiator, so it takes forever"

 

Me too, but I hate the ones were people just make broad assumptions about me ....I just don't understand these darn cooling systems!

 

What is glaring is that everything is working fine; the S30 cooling components are more than adequate for the VG30. I need more antifreeze and less water in the coolant.

 

You blew off a good suggestion, with the assumption that "new" means "working correctly". You seem to be over-complicating a simple system. There's no magic. The antifreeze/coolant ratio, and/or the capacity of the radiator, shouldn't affect the opening of the thermostat.

[BLOZ UP]

You blew off a good suggestion, with the assumption that "new" means "working correctly". You seem to be over-complicating a simple system. There's no magic. The antifreeze/coolant ratio, and/or the capacity of the radiator, shouldn't affect the opening of the thermostat.

 

Maybe I'm being ambiguous, I'm not talking about the opening of the thermostat. I'm talking about how once the thermostat opens, the engine (CHTS) takes a while, a long while, to come up to what temperature I'd like it at, 90 degrees C or so.

 

 

But Tony D also had a similar problem, so I'll just take what I can from his post.

[NewZed]

That works, but you did ask for advice in Post #12, after Tony D's comments. Seems like you just didn't like the suggestions, and followed with some thoughts that don't really fit the facts. Not sure a VG30 and an L6 are good comparisons either, plus the fact that Xnke has the cylinder 5 and 6 cooling modification on his L6. The water's getting kind of muddy here. I only got in to try to simplify things.