Normal coolant temperature

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rrrs
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Normal coolant temperature

Post by rrrs »

Hi, I am trying to confirm if my 85 635 is actually running hot or if it is normal temperature.
In normal, light load, AC not on, I am just under the middle mark on the gauge; looks perfect.

Once the load increases (AC on or longer up-hill, driving at higher rpm's) it climbs up to 2/3, maybe even 3/4.
Yesterday on a long uphill (driving at the good speed, 50-60mph) it was just keeping there, between 2/3 and 3/4; never touched the red, but not that far off. This was with pretty cool exterior temperatures....

So far I did following, but nothing seemed to change the behavior:
- Cleaned/flushed the whole system
- Changed the fan clutch as original one was easy to stop spinning with newspaper-test
- Changed the thermostat and thermostat housing
- Blead system really well; now, if I open the bleeder screw when under pressure there is just coolant coming; no air bubbles
- Changed electric fan thermo-switches; low speed is now at 80degree, high at 90degree.
- Confirmed that electric fan does work.

I do not see any indications of blown head gasket (no oil in coolant or coolant in the oil; no white smoke...).

Would this behavior be normal or, if not, what would be next step to fix (changing water pump, radiator...)?
plip1953
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Re: Normal coolant temperature

Post by plip1953 »

Is this new behaviour or has it been like this throughout your ownership?

Swapping out the radiator and/or water pump would clearly be potential next steps, but I just wonder whether trying a different/new temp sensor might be worthwhile?

On my own 635, in 30 years of ownership I don't think I've ever seen the needle go more than a fraction over half way.
Phil
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Jubilados
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Re: Normal coolant temperature

Post by Jubilados »

I’ve had E28s and now and E24 since 1992. In So Cal so it can get hot in the summer.
The only time mine have ever run above the mid mark is when something is wrong. Like an old radiator that is clogging and losing efficiency.
rrrs
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Re: Normal coolant temperature

Post by rrrs »

Thanks, I think I will try changing a water pump next; already got a spare on my shelf.
Radiator would be more expensive option; there is a Nissen radiator in the car, so was replaced sometime by PO; not sure when.

I am really not sure if this behavior was always there or not....when I got my car few years ago suspension was in such poor condition that one would not have much confidence to really push it beyond casual cruising speeds.

I have since do the full overhaul and upgrade of suspension, brake upgrade and new wheels/tires; the car now really handles and stops very well and once I started to push it a bit harder I really noticed it heats up beyond what I would like to see.
First thought it was only with the AC on, but even without it seems to be the problem.
I do not think it is a problem with the gauge because when just cruising on light load temperature stays very stable just below the half mark.
Jubilados
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Re: Normal coolant temperature

Post by Jubilados »

Hate just throwing parts at things, but seems like you only have the radiator and water pump left to to. And you already have a water pump on hand. So I’d try a new radiator at this point. I don’t mind buying a new radiator to replace an old with of unknown age/condition when I have a cooling issue. It eliminates it as a suspect, and will last a long long time.
Jubilados
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Re: Normal coolant temperature

Post by Jubilados »

And it seems like a good suspect.
At 60 mph your fan isn’t contributing anything, so it’s not that.
The water pump is a simple mechanical device, if it’s spinning and not leaking it’s almost certainly working (unless someone put on the wrong part).
Your radiator may be working with enough efficiency to keep your gauge in he middle at low loads, like idling, but not up to the task when you’re generating more engine heat.
Jubilados
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Re: Normal coolant temperature

Post by Jubilados »

One other thing I’d recommend is changing the stock AC cooling fan out for a modern Spal high flow fan.
Not so much for radiator cooling (it won’t help with your issue at 60 mph), but for increased AC cooling.
It pushes a lot more air through the AC condenser, is more efficient and also much lighter.
I did it as part of a whole system AC overhaul (I now blow 40 degrees on a 90 degree day). I was surprised at how old school the stock fan is.
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Ralph in Socal
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Re: Normal coolant temperature

Post by Ralph in Socal »

I would recommend a radiator replacement also as the radiator itself is not expensive (here on the mainland) but shipping to you could be expensive. Costs go up as you should also replace ancillary parts. Use distilled water (cheap) and BMW coolant or Zerex G05

Some recommend running just distilled water and "Water Wetter" in non- freeze environments. Good luck

Ralph
There is a very fine line between "Hobby" and Mental Illness.

85 635csi Zinno Auto
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rrrs
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Re: Normal coolant temperature

Post by rrrs »

Thanks for all the comments, they make sense.
Re. radiator replacement, would a nissen brand commonly available for +/-$200 be good option or would it make sense to "upgrade" to full aluminum versions available on e-bay?
Asking this as I am planning to turbo-charge the car in the future (already got most of the parts needed) and that would put even more load and heat into the engine.
Does anyone have some good or bad experiences with those ebay offerings; which one in particular?

Thanks, Robert
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86_6series
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Re: Normal coolant temperature

Post by 86_6series »

The best $ can buy. Read the reviews. With me, after replacing 2 BMW radiators within 30 years with the plastic
reservoirs that leaked when you looked at them, I was done. This is one fine radiator.

https://wizardcooling.com/i-30503452-wi ... l%3D635CSI
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anchored
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Re: Normal coolant temperature

Post by anchored »

I have a digital temp sensor and read around 75c-90c on average
SHRKATK - Red 87' 635csi
rrrs
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Re: Normal coolant temperature

Post by rrrs »

Hi, I wanted to post the update, good as a reference for others.
I did another good system flash and installed new water pump.
Then I filled the system with blue Zerex , but at lower concentration as there is no freezing here.
Did roughly 1/4 Zerex concentrate and 3/4 distilled water.

Car is now cooling perfectly, was never able to push it more than a mm over the center of the gauge; this is with AC running and pushing uphill.

What I noticed that last time I changed the coolant I did by mistake use concentrated Zerex thinking it was a pre-diluted one.
I believe this might have been the main reason for cooling issues as concentrate probably does not cool as good as water!?
plip1953
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Re: Normal coolant temperature

Post by plip1953 »

Nice to hear to got a result!
Phil
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