High water temp. Can’t figure this out.

[ewrjontan]

Didn’t see any bubbles but I also didn’t check with the car fully warmed up, might go and check out one of those testers.

I did some more bleeding. Bled with the motor on, heat at max, fan on low. Popped the bleed screw here and there until up to temp, revved, popped the bleeder several times. Took the car for a drive to my local hardware store and was seeing 194-198 occasionally hit 201 after idling at a light and would quickly drop down.

When I got back to the car (probably 15 min or so) I started it and saw 207. Normal, car had been sitting while off. But the whole drive home I was seeing 190-196 while moving. At a light it would get up to 198. Not sure what changed during that time but definitely seemed to be running a tad cooler on the way home and there was no change in temp. I was driving pretty hard (both drives) and made an effort to cruise at 4k rpm’s.

Only time will tell if anything really changed however and I highly doubt it because it was a beautiful 60 degrees out as opposed to a few days ago where the temp outside was 99…

[RRSperry]

210F at idle? Something isn’t right.

[ewrjontan]

I’m going to go ahead and order a thermostat. Got a track day next weekend. In the mean time I’m also going to grab a combustion tester and check that out. Crossing my fingers it’s just the thermostat. Sucks if it is though since it has 30,000 miles on it.

[blckstrm]

I hear you. I idled about 185 before fixing my stuck thermostat - even in 100+ temps. But at speed it couldn't stay cool - two laps and I was doing a cool down lap, even in the morning. It was stuck half open, so it took a long time to warm up and yet still didn't help much under load. That particular track day could have been a lot better.

But yeah, something is way off. You shouldn't be idling near that, especially with the weather that cool.

But I have hope it's just the thermostat. I don't feel like there's too much evidence it's a HG.

[ewrjontan]

Ok so let me get this straight. So at idle the temps should be lower? It makes sense compared to more heat being generated under load but I feel like if you’re in traffic, it’s warm outside, sitting stationary with no air flow i wouldn’t think it’s abnormal to have slightly higher temps at idle. Especially if you had only been at a stop light for a short time and the car hasn’t cooled down. Obviously mines quite a bit higher than “slightly.”

I should have a upper 80 degree day tomorrow so I’m hoping I can see what the temps are.

[zellamay]

Temps high at idle vs temps high at highway speeds... depends on what's wrong. That's one diagnostic tool: to know when it gets hot. A car that's setup and running properly will have, in general, same temps under all conditions. My oil temp goes up 5 or 10 deg at speeds over 70 + mph in AZ summers, but the water temp gage does not move from 12:00 position.

[ewrjontan]

Are you referring to the dash gauge? That needle will never move unless something is REALLY bad.

So realistically, what ever temp I am at at idle, should be relatively close to whatever I am running when moving? I havent driven the vehicle today yet but my temps while moving were sticking around 196-198 but as soon as I stop, it seems to drop down to 192-194. However, if I sit long enough the temp seems to get back to 198 or even a few degrees more. I basically have been assuming that the temp gauge is maybe catching up. As I approach a stop, theres less load on the motor/lower rpms, so less heat and also still getting air flow due to moving. Gauge reads lower, but heat builds back up do to being at a stand still.

I will check temps again this evening.

[RRSperry]

As a reference. My supercharged, no mechanical fan, 80C t stat, 88-92? Aux fan switch (whatever the fan delete one is), Stewart pump. Warms up pretty quickly to 180f when it’s not freezing. It basically sit very close to there. I sat in an airport parking lot on a 105f day with the AC blasting and it never got hotter than 205F. I’ve never see it that high driving. At a stand still with no ac, you can watch it go above 180, the aux fan turns on, it drops. Rinse and repeat. I once had a twig jam the aux fan, and it started going higher. Noticed it immediately, pullover, and saw it, removed it, replaced the fuse that blew, and back to normal. It’s behaved that way since I did the FDM some 20 years ago. If you have a mechanical fan and clutch, and a working aux fan, (working stat, and pump), no way it should get to 205 just sitting still.

if you have an IR gun, shoot the outlet of the tstat, and check the gauge. (a flir camera is great too.) I’d also check that the fan clutch is in fact working too.

[blckstrm]

Are you referring to the dash gauge? That needle will never move unless something is REALLY bad.

So realistically, what ever temp I am at at idle, should be relatively close to whatever I am running when moving? I havent driven the vehicle today yet but my temps while moving were sticking around 196-198 but as soon as I stop, it seems to drop down to 192-194. However, if I sit long enough the temp seems to get back to 198 or even a few degrees more. I basically have been assuming that the temp gauge is maybe catching up. As I approach a stop, theres less load on the motor/lower rpms, so less heat and also still getting air flow due to moving. Gauge reads lower, but heat builds back up do to being at a stand still.

I will check temps again this evening.

LOL - yeah, no, I think the only use for the factory gauge is to know when to take a cooldown lap or pull over.

I can't completely say right now - I'm in-between a bit at the moment. Not having the oil cooler in place with the new Z3 rad means the aux fan has a gap at the bottom that wasn't there before and won't be there after Monday. But for now it means both the aux fan and the fan shroud leave a gap where air can easily bypass the rad. So it idles hotter than it used to and hotter than I think it will after I install the oil cooler, but that's still only about 194.

But before, I idled at about 188 with a failed open thermostat. And it got much hotter when driving, but as I've mentioned I'm pretty certain it was failed only partway open.

Right now, the car's water temp when moving stays below 194, and stays about 190 unless I'm in dirty air. And I'm talking 100* ambient temps. Based on the volume of the Z3 rad and the placement of the temp sender in the block (or head or wherever it is), I suspect the thermostat is cycling or close to it at that temperature.

In the 3 weeks or so I've had the Z3 rad I've only ever gotten hotter than about 197 on track in 98* ambient weather (aside from that first night when I was still getting air bubbles sorted).

So if you're in that same ballpark or hotter - in much cooler weather - that seems like something isn't right.

Again, I don't see much evidence of a HG issue - this seems like a thermostat issue. And I'll note that it might have been high temps (before you were paying attention) that caused the rad neck to fail in the first place. So rather than this being a second complication, it might be the original cause of your first failure. Were you watching your data before the failure?

[ewrjontan]

Interesting. I was watching but I guess never payed attention to it. It could have been reading like it is now, But probably didn’t. I only really made sure to stay under 220 and it didn’t really seem to be difficult.

The temps definitely got higher after the radiator install so I was thinking perhaps I could have damaged something by running the car and not noticing the leak until a session or two that being said I still never let it hit 220, I always backed off at 218.

I drove today and it was about 60 degrees outside. Drove quite a bit and seemed to stay around 190-196. Even saw 189 for a brief period at a stop light. I feel like after the oil temp got up I started to see a bit higher ~198 maybe 201 while moving and then dropped back down to 196. Iirc this was on the highway doing 65-70.

I guess I’m sort of naive to how thermostats can fail. I always knew they could fail stuck or open but in this case, could it possibly be having trouble opening and closing? Like sometimes I’ll be running cool, then it’ll heat up pretty good and go back down. Most of the time it seems to be only fluctuating a couple of degrees. Seems like it is maybe not opening up/closing consistently? Is that possible?

Again, I will be running my combustion test tomorrow and also will see where I’m at with tomorrow being upper 80s.

[ewrjontan]

Alright so I drove the car today, about 85 degrees outside. Seemed to like to sit between 198 and 201 degrees while sitting at idle. While driving it somewhat stayed the same. However doing some spirited driving and hitting 80 mph on the highway staying around 4-5k rpm I hit 207 for a bit.

Ran the combustion leak test and had no issues there; fluid stayed the pretty purple/blue the whole time.

Question about the fan. I tested the actual fan and it operates fine if I short the wiring harness at both low and high speeds. However, I haven’t seen it turn on via the radiator fan switch. Now I did see it on a week or so ago after arriving home from my commute; this was on that 99 degree day I think. My question is, at what temp should it be turning on? The switch itself is the 91/99 degree switch but it is on the cold side of the radiator. So I checked to see if it it was on after parking my car today and the water temp sensor was reading 221. The coolant is just sitting there at this point and it’s always read high at startup with the car already being warm and sitting. I checked the fan and it still wasn’t turned on.

I’m assuming it’s not on because the temp on the cold side has not reached 91 degrees celcius or 195 Fahrenheit. But if that’s the case, the coolant is passing through the radiator and cooling quite well. I imagine I’d have to be running very hot at the hot side for the fan switch to read a high enough reading to turn on. Or is my fan switch dead?

I’m going to replace the thermostat, should be here by Tuesday but I wish I would have ordered the damn fan switch too at this point.

[RRSperry]

Only way to know if the actual switch is bad is to test it. Pot of water, thermometer, multimeter.

[blckstrm]

I got a cooler fan switch, but my recollection is the low speed came on about 203 and the high speed came on about 215. In either case there's no question it's not turning on - that switch is either dead or the fuse is blown. That's potentially your entire problem right there.

[ewrjontan]

Ughhh. Man. I knew I should have just ordered one. Fuse is working otherwise shorting the pins on the fan wouldn’t work.

[ScotcH]

Ughhh. Man. I knew I should have just ordered one. Fuse is working otherwise shorting the pins on the fan wouldn’t work.

dont you have a parts store in town? SHould have these in stock ... any Worldpac show can also get them same day.

[ewrjontan]

Cheaper though online for an oem or genuine part. All of the general auto stores have shit brands. Unfortunately, all places have a two to three day shipping delay on their genuine parts. Going to call my stealership tomorrow so see if they have one in stock.

Edit. So I grabbed my laser thermometer and hit the tstat housing/sensor as well as the fan switch. Tstat sensor (inline with the upper radiator hose) seemed to be spot on with my gauge and thermostat housing.

Fan switch was reading significantly lower. Measuring the thermostat at 203 and the radiator fan switch was reading under 190 so there’s no way that fan would be turning on at that point.

I did notice something interesting. My initial temps were taken when I first arrived home and just parked. After several minutes of idling the gauge would still read 201-203. However any measurements taken after were significant lower. I tried and tried to get a tstat reading and maybe once did I see 200. All the other times I saw 190. At the water temp sensor itself i was having a hard time getting over 190.

So what gives? Is this because the thermostat has closed and thus the water in the upper radiator pipe is stagnant? Could my actual temp at the head be significantly lower? The only spot I could measure without obstructions was close to the VANOS and it did read a lot lower than my thermostat housing. Ughhh. Could all this just be due to the location of my water temp sensor and it being located in the upper radiator hose?

While driving today I tested the fan to see if it at least works with the AC and it does. That is probably why I *think* that I’ve seen it on before; because the ac was running. I noticed that at highway speeds and the fan on, the temps were more consistent, holding around 198. As soon as I turned the AC off it went down to 196. Not sure if this adds anything to this but figured I’d mention it.

[RBNetEngr]

The thermostat doesn’t operate as either Fully Open or Fully Closed. It can also be partially opened.

So, it sounds like your thermostat may be stuck partially open, or for reason cannot fully open. So it won’t allow full flow of coolant, and causes the coolant temp to stay higher than it should.

[ewrjontan]

Gotcha. I think that’s it more so than my fan switch. It doesn’t seem like the cold side is getting anywhere even close enough to flip on and even if it was broken, it doesn’t seem like the fan makes too big of a difference at idle based on how running the ac doesn’t seem to change my temps overall.

So just to verify and try to make sense of this. If the thermostat is partially opening, that means less hot coolant leaving the engine and less hot coolant making its way through the radiator. The radiator is doing its job and cooling whatever coolant is making it’s way through. The cold side of the radiator stays relatively cool because only a small amount of coolant is going through it. If the proper amount of coolant was flowing through, the cold side (lower radiator hose) should be quite a bit warmer if not the same temp as the upper hose?

[ewrjontan]

Ugh. So I pulled the thermostat, through it in water and tested it against my new one. Seems to be working in similar fashion to the new one. I will say that there was a point where the new one completely closed and the old one was maybe 95% closed; like a minuscule amount. Maybe opened and closed slightly slower or faster than the new one. Hopefully the old one is just inconsistent and the new one fixes the issue but I kind of doubt it. I’m starting to think that maybe my water temp sensor/gauge setup (innovate motorsports) is not accurate. Read a review on google just now saying their gauge read 18 degrees higher than with a calibrated gauge. Could be it. I wish I could have taken better notes on my temps when I installed them (this was before the radiator replacement)

[pbonsalb]

Seems like a good idea to remove your innovate sender, attach some longer wires to it and put it in hot water that you can verify the temp of using another thermometer.

The 91/99 fan switch turns on at temps higher than 91/99 in the head because the cold side of the radiator should be colder than the head.

You can put a temp sender in the block drain with an adapter bushing. Many put it in the thermostat housing and it seems to work fine. You can put one in the TB coolant port in the head but you need the right adapter and the right sender — it is not easy to find the correct combination because the port hole is so small.

You can put the fan switch in the block or head as well, and extend wiring. This does not let the radiator do its work first. But the stock clutch fan is always turning even if not fully engaged and providing some cooling effect and it has no direct connection to the cooling done by the radiator. As I understand, it senses temp through the bimetallic spring inside the clutch (similar to the radiator fan switch but purely mechanical rather than mechanical/electrical) as the water pump heats up and the heat travels down the pump shaft.

[ewrjontan]

Yeah I’m definitely going to just pull my sender and bring a pot of boiling water outside. I’m praying to god it’s just miscalibrated and that I’ve just been chasing my tail for no reason

[blckstrm]

I didn't boil my thermostats together when I just replaced it, but you could BARELY tell them apart sitting side by side cold. It was less than 1/8th of an inch gap. So even a very small difference at closing can make a huge difference. I wouldn't be surprised if it was the same story at open - very little difference to the eye, but a lot of difference in terms of flow.

Also, a bad fan switch matters more than you think - that auxiliary fan makes a big difference. An AC condenser adds a LOT of heat - if you're ever had the aux fan fail it's very clear based on your running temps. So under normal circumstances, yes, your temps don't change when you turn your AC on because the aux fan is more or less built to manage the condenser and provide a little additional cooling to the rad. But it was failing, you'd know it.

Between that and a thermostat not opening all the way, that would be enough to get you to the temps you're seeing.

When I had the factory fan switch I'd read 203* from OBDII when low speed would kick on, and around 215* when high speed would kick on. I just saw your edited post above - does that mean you're not reading via OBDII, but from an aftermarket sensor installed in the upper hose? If that's the case then the following is a little less authoritative, because the temps could be somewhat different.

Have you ever checked what that aftermarket thing is telling you vs what the car is telling you / what you're getting from the OBDII port? That could be enlightening.

I do disagree with an assessment that you weren't getting enough water flow / hot enough water by the time it crossed the rad to turn on the fan switch. That's only true to a certain extent (I did notice that the new Z3M radiator is cooling the water better and therefore slightly delaying the temp I read via OBDII where the fan turns on, especially at low revs / low flow rate. So I'm seeing just slightly higher temps before I'm seeing the voltage drop from the fan (in my case fanS) turning on. But like 1-2*C - not 10*C.).

But you said you hit 220 and no fan on - even at low speed (with AC off). I don't care where in that system you're reading - that's just not possible unless the switch is bad (given you jumped the fan and it and the fuse were good). Or the thermostat was all but completely failed closed.

At this point I think you've probably got the new thermostat in. I'd just go ahead and replace the switch too and be done.

[ewrjontan]

No obd reading as the car is a 95 so no way to really know for sure other than the range that the stock dash gauge provides and that’s right in the middle.

The thing with being 220 without the fan on, that was on startup after being parked on a hot day. Coolant not flowing and just sitting. Cold side would t really be that hot so the fan wouldn’t turn on at that point necessarily. As soon as the car was turned on the temps quickly dropped.

[ewrjontan]

Welp. Bad news but also good news I guess? Temp sensor seems to be reading accurate. Tested some hot water in a mug and threw the sensor in along with my thermometer. The thermometer seems to be relatively accurate (water starts boiling about when it should) and the water temp sensor seemed to be within a few degrees of the thermometer depending on if I had the sensor against the walls of the mug or free floating. I tried to get it as close to the thermometer probe as I could. But yeah, temps seem to be relatively close so I believe my sensor is reading as it should. Although I was hoping for it to be reading 20 degrees high.

Anyways, got the thermostat and sensor installed. Just need to let things dry a bit. Also tested my new fan switch which seemed to be turning on as it should, both low and high speeds. Will hopefully get everything out back together tomorrow without any leaks. Will be vacuum bleeding again so I’ll be sure if I have a leak.

I do plan to test my old fan switch to see if it is working as it should.

[pbonsalb]

Which thermostat did you buy? I have been using 80C for about 15 years, along with the 80/88C fan switch. For years, the car was a year-round driver though in recent years it has not been driven much. The only time it ran at 80C was winter and there was still heat. A good person to search for posts from is ScotchH, who has a lot of track experience and has posted typical operating temps before, but maybe those are AC delete cars and that does make a difference.

I did not like the way the harness connected to the lower temp fan switch — a locking tab has to be cut off the switch so I later changed the switch to the bigger early one and spliced in a section of harness that fit (I think it was actually the aux fan power harness from a salvage engine harness I had but can’t recall for sure). Splicing in the lighter duty harness end that fits the smaller switch would be better if you find one.!