Coolant circulation issue? M52B28

**bmwdirtracer** · 07-14-2018, 09:56 PM

There's something quite odd about those temperatures. First, I'd have to wonder why the top hose is showing ~185, but the top of the rad is showing 210. While there's a significant difference in reflectivity, it shouldn't be 25 degrees.

I've got to say that I've never seen any radiator cool by 130 degrees! Hell, it's a single-pass radiator, yet between top and bottom on the left side, there's a 90 degree drop, before the coolant has even run through the cooling tubes of the rad, much less in front of the fan!

IF the engine were truly getting a full supply of 90-100 degree (F) water, there would be no possible way for it to heat that water up to 210 degrees, in a single pass, especially at idle. (Imagine starting a car for the first time in the morning...it takes more than 30 seconds for the temps to come up to normal).

Personally, I think the bottom 2/3 of your radiator is largely clogged, because there's no other way to explain the MASSIVE temp drop, especially from top to bottom on the driver's side, before the coolant even goes through the tubes.

**323i E30** · 07-15-2018, 03:15 AM

Hi Chris,

Maybe my $20 temp gun is measuring too wide, taking the open space next to the hoses in consideration too.

That does make sense, but wouldn't a very slow circulation explain all of that too? Is that even possible with a well functioning waterpump and thermostat?
While flushing the radiator the water came gushing out and really contained almost zero rubbish.

Originally Posted by DerbyDave330

Might be worth trying to flush the block perhaps? all hoses off, radiator. duct tape up your hose pipe and see if everything's flowing freely.
Could pay to investigate this all the way:-)

Welcome! Thanks for the honour of your very first post here

That is indeed worth investigating.

**323i E30** · 07-15-2018, 06:47 AM

Another thing I noticed: heater works and blows real hot air, but has minimal effect on the coolant temp..!

**DerbyDave330** · 07-15-2018, 07:50 AM

Cheers pal. Funnily enough I'm in the process right now of fully replacing the cooling system on one of my m54s right now.
So have you swapped in an e36 engine into an e30? is that right?

**bmwdirtracer** · 07-15-2018, 08:41 AM

Certainly "gushing out" would seem to indicate that the rad is fine....but I just can't explain the 90 degree difference between the top and bottom of the rad on the driver's side, right next to the plastic end tank, if the lower tubes are actually transferring coolant.

**ross1** · 07-15-2018, 10:32 AM

I've NOT read all the posts here so take my thoughts with a grain of salt.
If coolant is circulated TOO quickly through the rad the heat isn't dissipated as well.

**bmwdirtracer** · 07-15-2018, 12:22 PM

Have a look at the video.....

**Breeze1** · 07-15-2018, 05:54 PM

The way the temps brutally drop from top to bottom on the driver's side and then seem to cool down progressively from driver's to passenger's side AND the fact that the temp is lower in the top hose than in the top of the radiator means in my opinion that the clogg is located "north east" of the radiator if you are facing the car. Coolant (and heat) are accumulating there

**323i E30** · 07-22-2018, 06:40 AM

The 10th of August it'll be back in the shop. I've asked them to flush everything they can flush, flush it some more, and then fill her back up with blue coolant.
I'll update when I have news. Thanks for the input guys! Much appreciated.

**323i E30** · 08-12-2018, 03:59 AM

Got the car back last Friday.
They flushed and cleaned everything, and filled her back up with blue coolant. The guy told me that there was so little dirt coming out of there that he was not convinced that that would have caused any serious restrictions though.
Because of that he left the thermostat out, in order to get as much circulation as possible for the time being. Again with the note; see how it goes, and let us know.

I took the car for a drive yesterday twice for 45 minutes, and the last time I left it idling for another 15 minutes to see how it behaves.
During the drives the temp stayed in the blue for relatively long before reaching the minimum temp mark. It would go up a bit at idle, and drop back to the minimum mark while driving.
Anyway, nothing out of the ordinary there for a cooling system without thermostat..!
Temperature difference between top left- and exit hose is 20-25 degrees now, so looks like this has been solved.

Silly thing is that I don't know what the issue was now, as the flushing might have solved it or both old and new thermostats were bad after all. Kind of annoying, but ok..
I'll let them finish the job by reinstalling a new thermostat, make up the bill and be done with it!

Thank you guys for your time and advice!

**ross1** · 08-12-2018, 08:01 AM

You need to re-install a(perhaps not the one you have)thermostat.

**323i E30** · 08-12-2018, 08:27 AM

Originally Posted by ross1

You need to re-install a(perhaps not the one you have)thermostat.

Absolutely!

**bmwdirtracer** · 08-12-2018, 09:09 AM

Sometimes, brand new OEM parts are bad, right out of the box, too.

Just Friday, I had a 2013 Mercedes with a code for failed LF wheel speed sensor; so I installed a brand new Ate sensor....and could not make the code go away! Swapped left for right, and the code followed the brand new sensor ! Replaced the new sensor with another brand new one, and all was well.

It's just too bad that you have to open up the system yet again, but I'm glad you've gotten to the bottom of this issue!

**323i E30** · 05-18-2019, 09:04 AM

Originally Posted by bmwdirtracer

How long have you had that blue hose? I remember, many years ago, Jim Rowe (Metric Mechanic), explaining to me why BMW upper and lower hoses are belled at the ends, and get smaller: it keeps the coolant from "tripping", and causing a turbulence which results in a flow issue......just like intake air.

(...)

Originally Posted by bmwdirtracer

(...)
And, if you happen to have the old top hose laying around, I think I'd swap it, in case the diameter changes inside those pretty blue hoses are causing an issue.
(...)

This pretty blue hose has found a new reason to live today.
No, there was no way to make the hard plastic tube fit

It's in a very small area, so had to make it work like this to have the tap face the right way..

The E30 is still running strong with no issues whatsoever btw. Thanks again for all the help!