engine swap M20 Swap Running Too Hot

[potentialm20]

I completed an M20 swap in my 2002 about a year ago.  Then I got distracted with other projects and the car just sat.  I am now driving it again and it is running really hot.  Like, almost touching the red, hot. 

 

Cooling system details. 

 

New water pump

New thermostat

New all aluminum (ebay) radiator

http://www.ebay.com/itm/271010365530?item=271010365530&viewitem=&sspagename=ADME:X:AAQ:MOTORS:1123&vxp=mtr

 

12" puller fan (yes it is pointing the right way)

 

I am using the stock 02 gauges and the m20 temp sensor, but I believe that this should work fine. 

 

There is no oil in the coolant or coolant in the oil.  I suppose I should do a compression test but I don't really want to consider that as a cause. 

 

Any ideas on trouble shooting this or hopefully a smoking gun that I am missing??

Edited July 28, 2013 by potentialm20

[Simeon]

Thermostat was new at the time of the engine swap or new now?

Can you feel hot water going into the rad via the top hose?

Did it ever run ok? Did you add any coolant recently?

[Pierre]

We need more details.

 

Did you install all the coolant hoses just like they were in the original car?  Is your coolant overflow tank at or above the top of the radiator?

 

Do you have the mechanical fan?

 

First, you have to see if coolant is flowing through the radiator.  A great tool would be an infrared thermometer.  They are getting pretty cheap.  (around $30 at Harbor Freight.)

If you are in fact getting coolant through the radiator and it shows to be very hot, you can then compare the temp in and temp out of the radiator to see if it's actually effectively doing any cooling.  You could then determine if the engine is just producing way too much heat, or if the cooling system is not doing appropriate cooling or if you have a gauge issue.

How fast is the temp rising?  Is the gauge bouncing around?  What kind of driving are you doing?  How does it respond to different types of driving?  Highway cruising, around town, redlining on the track when is 110 outside?

Is the fan going on?  At what temp?  Or is it manual?  Does the temp drop when the fan kicks in?

Is this a stock M20?  Is it a B25 or B27?  If it's a B25, do you have an oil cooler?  

[potentialm20]

Coolant is flowing and radiator is getting hot (both hoses are quite warm, maybe suspiciously warm in case of return hose..)

 

The thermostat is new as of a couple days ago (tstat is opening)

 

All front of motor hoses are plumbed in stock fashion (heater core is bypassed)

 

Coolant res is highest point

 

Type of driving doesn't matter, gets hot no matter what.

 

Mecanical fan doesn't fit in an 02 but I have a 12" electric (might add another)

 

I am going to install another fan and some ducting and see if that helps

guage doesn't bounce or jump on start up.  Rises very predictably. 

fan is manual, running it at all times lately.

I have been wanting an infared thermometer, probably as good an excuse as any to buy one.

Edited July 28, 2013 by potentialm20

[Simeon]

All front of motor hoses are plumbed in stock fashion (heater core is bypassed)

Hmm read a post recently advising against bypassing the heater (on M10's) as it just dumped hot water from the head straight back to water pump. Better off just blocking off the hoses to simulate a heater valve.

Not saying that is all of your problem but it might not help.

The next thing to ask is, are you sure that you got all air out when you swapped the thermostat?

[dbmw2002]

Critical point on all BMWs is air in system causing hot pockets, also too far advanced timing can turn a tame motor into a rabid block heater. maybe a good old fashioned pressure test might be advised. Check all hose clamps and rad cap

[tjones02]

Best advice I have for you is to go get a infrared thermometer from Sears, Harbor Freight. Preferably with a red laser pointer light. Then, measure the temp around the temp sensor for me when the engine is "hot".

A question: while running does coolant flow from the radiator bleed hose to the reservoir? If you have to pull the hose off either end and unplug the radiator, expansion tank or both. If coolant doesn't flow through this hose the engine will nearly immediately overheat.

HTH

[Pierre]

The bottom hose should be much hotter than the top hose.  It's hard to tell by feel since hot is just HOT and it's hard to tell between hot and very hot.  The temp going into the rad should be under 220 and coming out should be significantly less, like 140.

An air bubble would definitely cause havoc in the cooing system.

But I would not overlook the gauge.  Different driving styles should make a difference in the way the gauge reacts.  Make sure you wired your gauge to the correct sensor and that your grounding is solid.

[potentialm20]

No air bubbles, bled the system multiple times (on an incline to insure the valve was highest point on the engine). 

 

I can see a current in the expansion tank when the engine is reved so coolant is certainly flowing.

 

I like the heater block idea.  Although I'll probably just finish plumbing the heater core into the system to test that theory. 

 

I am also curious about the advanced timing idea.  My initial reaction was dismissive as the car has an ecu so I know I haven't screwed the timing up myself.  But it is chipped so maybe the timing is advanced.  I will try stock chip and see if there is a difference. 

 

My vacation starts Tuesday so I should be able to get lots of work done. 

[potentialm20]

No air bubbles, bled the system multiple times (on an incline to insure the valve was highest point on the engine). 

 

I can see a current in the expansion tank when the engine is reved so coolant is certainly flowing.

 

I like the heater block idea.  Although I'll probably just finish plumbing the heater core into the system to test that theory. 

 

I am also curious about the advanced timing idea.  My initial reaction was dismissive as the car has an ecu so I know I haven't screwed the timing up myself.  But it is chipped so maybe the timing is advanced.  I will try stock chip and see if there is a difference. 

 

My vacation starts Tuesday so I should be able to get lots of work done. 

[tjones02]

Worst case scenario is combustion escaping into the cooling system. That can over pressure and overheat a system quickly, before the t-stat gets a chance to open. You can easily not see oil/water mix if that's happening. Didn't wanna go there till I heard that you were getting good flow. I still wanna see the temp at the switch housing compared to the gauge.

[tjones02]

Any word on temp?

[potentialm20]

I got really distracted doing body work today.  I did run the car up to temp this morning while it was cool out and it went up to 5/8 or so and held.  This was reassuring.  My buddy is loning me an infared thermometer so I should know more soon.

[Simeon]

Off the Wall suggestion but is the temp sender on the M20 the same as an M10? Calibration the same?

[tjones02]

Yes the temp sender for the gauge is the same between '02 and E30...