recon engine and still problems

[chrisbmwe30]

Hi i have 91 318is m42 engine

engine has been reconditioned 3 months ago and since piecing it back together i have had a persisting over heating issue.
all new heater hoses and vacuum lines
new radiator
new wpump
new fan clutch
new o2 sensor
new thermostat has been changed 4 times as the bottom hose remains cold and i was worried about it being faulty. has been installed with the long end of tstat going into the block
system has been bled multiple times with the car a good 50cm in the air.
coolant temp sensors on the head were replaced when the rebuild was done.
again today i jacked the car all the way up and bled the system had it running for over 2 hours and was topping up and bleeding and it still gets just over half between the half mark and the 3/4 mark on the temp gauge
also the heater has been bypassed due to a faulty heater valve/tap and 'the mess under the intake mod' has been done during the rebuild.


symptoms exhaust blows a small amount of steam from the exhaust
engine runs and drives incredibly well
gauge creeps up
bottom hose remains cool to touch in comparison to top hose and radiator return hose
ac fan does not kick in, even when i flick on the ac to manually swit5ch in on temp sits just over half.

is it really possible to get that many tstats that are faulty also a small hole has been drilled to help self bleed with the hole at the top of the tsat when installed

any advice would be great

[oldmann]

When you say reconditioned, how much machine work was done to the head and block?
Or just taken apart, replace some bits and new gaskets.
Head on an M42 comes off, most times it needs to be resurfaced smooth and flat for the head gasket to seal properly.
Steam out the exaust? Water getting into combustion chamber past the head gasket. Need to do a leak down test of the head.
Or apply pressure to the cooling system, find out if it will hold pressure, Use no more than what the system is designed for.
Does the water level drop after the test? where would it go, into the combustion chamber if its not turning up in the oil pan.
An old radiator cap drilled and fitted with a quick coupler will let u hook up compressed air to the cooling system. Use the regulator on your compressor to keep the pressure down. Some where close the radiator cap put a pressure guage and a valve to isolate the cooling system. Charge it up and see if it will hold pressure.

Good Luck

[chrisbmwe30]

The head was pressure tested, faced, vac tested, valves faced, seats cut, beed blasted, reassembled, lifters bled, and block was decked. Will a compression test give any guidance to if the head has been damaged? Any idea why the bottom hose would still be cold? It also feels as though the radiator remains cool.
Will look into a leak down test involves.
Thanks for your help so far

[roguetoaster]

A few things I see, one you jacked the car up to bleed it? The usual process involves the bleeder screw next to the radiator fill car, which means it can be done on the ground. Next, where was the hole drilled, in the thermostat or the housing for same? There is also a preexisting bypass line in the thermostat housing which can be gunked up if gasket maker is used on the thermostat housing gasket.

One aside, what is a small amount of steam, and is it at idle of does it increase with RPM? If it increases I would guess that either the shop missed a crack, has happened before, or it was just on its way out and cracked upon reassembly.

[Ryann]

http://www.r3vlimited.com/board/showthread.php?t=230380

Do this and your issue will disappear.

[chrisbmwe30]

sorry for the late reply.
its only a small amount of steam probably nothing just being parannoyed.
the hole was drilled into the top of the outer ring of the thermostat not into the 'guts' of it so to speak.
i have ordered a 71c thermostat and i will be installing it tomorrow and cleaning out the groove in the housing and following the bleeding instructions provided in a reply to my post.
i will let you know how it goes.
I priced up a infra red thermometer but is not something i want to spend over $100 on it this stage. if the problem persists i will be taking it to a BMW specialist mechanic local to me and have them inspect it.

what are your opinions on such a low temp tstat? keep in mind im adelaide australia (we dont get snow here)

It s from an m20 as the m42 didnt have one made for it in such a low temperature (what im told here in australia, adelaide) but have been told it fits into the housing and block perfectly.

Thanks for all your help and ideas so far

[FLG]

Long shot but are you sure your installing the thermostat the correct direction?

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[chrisbmwe30]

yeah im a %100 sure the long part of the tsat going into the block. let me know if you think any different.

[FLG]

No that sounds right...hmm


You make no mention of new hoses? One could be internally collapsed.

Changing to a lower temp stat isn't going to help


Nvm re read new hoses...


Its very possible you have a restriction somewhere in the radiator...new or not. Have the old one around still?

Or a bad wp.


I'd take Ryanns advice first and make sure the bypass is clear and its getting bled completely

Tough to say for sure

Another edit: Are you saying it just goes a bit past the half way mark on the gauge? If so that's completely normal.

Example



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[chrisbmwe30]

Yeah your picture is about correct that's where it got up to idling for over 2 hours and repeating the bleeding procedure several times throughout that time. Im still concerned just because of how cold that bottom hose is in comparison to the looped heater hoses and the top hose. I'll try the above bleeding etc tomorrow with the new tstat and report back.

[chrisbmwe30]

Do I need to drill a small hole in the new thermostat? Or is the bypass groove enough once I have cleaned it out and inspected it?

[FLG]

That's exactaly where it should be. Take it for a drive and see if it stays there. Though chances are if it idled there it won't be going up any further.

You say "bottom hose remains cool to the touch" in comparison to top hose and rad return hose....what hose are you than referring to?

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