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BDA overheating


BlueBDA
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My 1700 BDA has been running very hot, and overheating and spitting up coolant on track days. I'm sure this has been covered before, but I never seem to be able to find what I'm looking for when I search the site.

 

Temp climbs steadily until it hits maybe 110C per my gauge. 

 

I have replaced the fan switch and fan comes on reliably.

 

So I bought a new 160F (71C) thermostat, which I was just going to install. My system is open to atmosphere, with a rubber hose draining into an open overflow bottle. I assume the thermostat and housing are the same as in a crossflow.

 

Questions:

 

- How do I fill the system with coolant? I never thought about it til now, but with the engine cold the thermostat is shut, so the coolant won't pass it to fill the block.

 

- Should I drill a small hole in the thermostat to allow the block to fill, as some online have suggested?

 

- How do I get all of the air out of the system?

 

- Torque specs for the two housing bolts?

 

- Should I use any RTV on the gasket? There wasn't any there before - the old gasket came off pretty easily, but again, some folks online say to use some RTV.

 

- Could there be any other reasons why it overheats?

 

Thanks in advance for any answers.

 

 

 

 

 

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FWIW: I fill my system by parking on an angle (my yard) such that the overflow tank is above the return pipe. This is combined with Tom's trick of using a screwdriver to bleed air from the return hose/pipe junction.

Years ago when having overheating troubles i also drilled extra holes in my thermostat (someone's advice) and haven't had trouble since. 

Even though there is already a small bypass I don't know if this helped by addressing an airlock or just increasing coolant flow the necessary amount. 

 

 

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Do you have a heater core? Usually it ends up being a high point in the system.

 

During my troubleshooting I've bought the peak/prestone radiator flush kit which comes with an extra inline valve to install at the back of the motor and I've been happy with the amount of air that I can quickly release by using it

 

image.png.a7ce8448e69c1d3163814c358c069d2b.png

 

https://www.amazon.com/Prestone-AF-KIT-Flush-Fill-Kit/dp/B000CCFY5W (or any parts store for blue Peak unit)

 

Your system isn't pressurized? If that's the case the funnel can be a lot of use to you. I had to make my own adapter to fit my specific overflow but it fits most vehicles. I know mechanics use them all the time. Creates the high point, gives access, allows things not to spill during expansion and overall a very useful tool at my disposal. Allows to see bubbles come up etc. 

 

image.png.0466b9f37b7c203b280c5889fec96b54.png

 

https://www.amazon.com/gp/product/B072BWG5GF/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

 

If my thread is any indication there is a million reasons why something overheats. Start small and go from there. Off the top of my head - Radiator blockage, running lean, air pockets, sticking thermostat, heater core blockage, blown head gasket, broken water pump, not functioning fan, blocked passage way in the motor and more. 

 

Does it only over heat while use and fine idling/parked?

 

 

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Lets keep it simple for now.  No need to assume the car has all the STDs that Vlad's car has.  

 

@BlueBDAJeff - Can I please clarify If its a pressurized system or not?  You say it is open to atmosphere which I read as unpressurized but most pressurized systems have a sealed catch tank for overflow.  Is it sealed cap?   Reason I ask is first check point is the radiator cap - do you need a new one or one with a better pressure point?

 

Good re the fan switch check.  What trigger temp does it come on at?  Thermostat temp hopefully?  How did you test that?

 

Assuming thats ok, then you look to the thermostat and whether it is opening correctly or not.  Test what you have now in a pot of increasing water on the stove with a thermometer or just bite the bullet and install the new one.  If you have no other symptoms at this stage, I would suspect thermostat as the culprit.

 

Like @wemtdPaul noted, I am a fan of drilling one or two small holes in the thermostat so coolant is always circulating to some modest degree.   

 

While those bucket things Vlad posted a pic of work well, sometimes you need to study the cooling system as decide if there could be a localized point of air getting trapped and install a bleed valve there.  Unlikely but I mention it, just in case. 

 

 

 

 

 

 

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As I (very) vaguely recall, this car has had some overheating issues since the the BDA transplant for the original X-Flow??? Still one of my favorite looking Caterhams (if not all-time favorite). I am sure you will get this sorted.

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Thank everyone for responses so far.

 

Of the list that Vlad gives above, I am relatively confident that my radiator is fine, I'm not running lean (probably a little rich, but I'm ok with that), and head gasket, water pump and fan are fine. I'm hoping it's just my thermostat, but we'll see.

 

System is not pressurized.

 

The radiator has no cap.

 

There is a cap on the thermostat housing (of course), and an overflow tube that runs into an overflow bottle. The overflow bottle has no cap on it; the tube just goes into the open bottle. One thing I realized is that that tube is kind of short, i.e. it doesn't extend very far into the overflow bottle. So I'll put on a new tube that extends to the bottom of the bottle, so in theory the system could suck coolant back in when it cools.

 

What size holes to drill in the thermostat? 1/8"?

 

Any further thoughts on bleeding air from the system would be appreciated. I assume that I can run the warmed-up engine with the thermostat housing cap off, and add coolant as needed?

 

I assume no RTV on the gasket?

 

Lastly, does anyone have the thermostat housing bolts torque specs?

 

 

 

 

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Yes “small” holes ~2-3mm diameter per memory. Will try to measure  my spare this afternoon.

which gasket/RTV are you referring to?  I use RTV on my water outlet-engine as there is no gasket.

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40 minutes ago, ashyers said:

Pressure test that cap on the T-stat housing.

 

Has the car always run hot when run on the track?

Why would pressure testing the cap matter if it's a non-pressurized system?

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My guess is the system is pressurized during operation. The cap on the t-stat housing should have a spring to hold the sealing surface down. A new cap rated at 10 to 13 psi is an inexpensive experiment.

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1 hour ago, wemtd said:

(Calling Croc) why a non-pressurized system? I thought we want extra boiling point elevation gained with pressure?

 

@wemtd and that is why I am confused.  Normally I would expect to see a pressurized system because you want the extra boiling point gain.  

 

You can run an unpressurized system but most engines operate at better combustion efficiency (with more power etc) at some elevated temperature and the problem is that temperature is too close to boiling point such that an unpressurized system will not work with the normal temperature variations you get using a thermostat and localized hot spots or environmental condition stresses.   I have not heard that a BDA or a crossflow would want to operate at 71 degC - seems low but assume @BlueBDAJeff checked it?

 

Cars moved from unpressurized cooling systems to pressurized ones around the 1940s.   I ran an unpressurized system on my old Caterham Zetec SVT when it was running Evans Coolant because the liquid allowed a better tolerance of temperature range from improved cooling via liquid transference.  I was experimenting - it worked well but I did not think it was doing anything special that justified it was a better solution than a regular pressurized system with regular coolant/water mix.  

 

@Kitcat I don't recall any overheating on this engine.  In its earlier crossflow iteration it did once overheat but Stewart stole the BDA out of his wife's Elan to install in the Caterham, which is how it ended up with a BDA.  

 

So if genuinely unpressurized then a cap should make zero difference in this puzzle since it is an open system?  @BlueBDAJeff - is the thermostat housing cap pressure rated?   Should not be based on your earlier comments but just checking as both @ashyersand  @coffee break have raised very good points.  

 

@BlueBDA Jeff - for avoidance of doubt, in the photo is the coolant catch tank the plastic one mounted to firewall?  The metal tank then is the dry sump oil tank?   Does the coolant overflow tank vent excess pressure?  Or is it just a hose stuck through the side of the tank?  I.e. it vents via hose entry?

 

Lots of questions:

- Yes - a single 3mm hole should do it

- What gasket?  On thermostat housing cap?  No RTV

- Yes to filling via thermostat housing cap.

- Don't know bolt torque sorry.

 

 

 

 

 

 

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I think that is a pressurized system.  Raceline uses the same thermostat housing in its water rail.  It's designed so the overflow port which feeds the expansion bottle is only open to the system when the pressurized cap hits it's limit and the base retracts.  Otherwise it is sealed.

 

-John

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21 minutes ago, Croc said:

 

@wemtd and that is why I am confused.  Normally I would expect to see a pressurized system because you want the extra boiling point gain.  

 

You can run an unpressurized system but most engines operate at better combustion efficiency (with more power etc) at some elevated temperature and the problem is that temperature is too close to boiling point such that an unpressurized system will not work with the normal temperature variations you get using a thermostat and localized hot spots or environmental condition stresses.   I have not heard that a BDA or a crossflow would want to operate at 71 degC - seems low but assume @BlueBDAJeff checked it?

 

Cars moved from unpressurized cooling systems to pressurized ones around the 1940s.   I ran an unpressurized system on my old Caterham Zetec SVT when it was running Evans Coolant because the liquid allowed a better tolerance of temperature range from improved cooling via liquid transference.  I was experimenting - it worked well but I did not think it was doing anything special that justified it was a better solution than a regular pressurized system with regular coolant/water mix.  

 

@Kitcat I don't recall any overheating on this engine.  In its earlier crossflow iteration it did once overheat but Stewart stole the BDA out of his wife's Elan to install in the Caterham, which is how it ended up with a BDA.  

 

So if genuinely unpressurized then a cap should make zero difference in this puzzle since it is an open system?  @BlueBDAJeff - is the thermostat housing cap pressure rated?   Should not be based on your earlier comments but just checking as both @ashyersand  @coffee break have raised very good points.  

 

@BlueBDA Jeff - for avoidance of doubt, in the photo is the coolant catch tank the plastic one mounted to firewall?  The metal tank then is the dry sump oil tank?   Does the coolant overflow tank vent excess pressure?  Or is it just a hose stuck through the side of the tank?  I.e. it vents via hose entry?

 

Lots of questions:

- Yes - a single 3mm hole should do it

- What gasket?  On thermostat housing cap?  No RTV

- Yes to filling via thermostat housing cap.

- Don't know bolt torque sorry.

 

 

 

 

 

 

You are right Croc, a trip down memory lane, via this Forum’s search function, shows Stewart had some initial low oil pressure issues, followed by some oil leak issues, all resolved, some during BlueBDA’s current ownership.

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If not pressurized, then a longer tube won't do anything because the inverse would also be true and there would be no vacuum to suck coolant back in...

 

If pressurized, then you could be low on coolant just due to repetitive dumping of coolant into the recovery tank/overflow voir without the ability to recover it.

 

Easy to tell looking at the underside of the cap.

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I agree with John.  Believe it’s “unpressurized” because it vents to an open catch tank.  I think of a pressurized system as onethat is completely closed, including the overflow/expansion tank.  With the open tank, you’re dependent on the cooling of the engine and (I think) resulting decrease in pressure to suck the coolant back into the system.  So, it is important that the tube extend to the bottom of tank, otherwise it won’t suck the coolant back in.  Not that it always does regardless.🙂

 

 

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Here is a picture that shows the pressure cap and thermostat housing so you can see how they work together.  Regarding the tube in the overflow tank, it's best if the end is cut at an angle to ensure that it doesn't' seal against the bottom and prevent the flow of coolant under suction.

 

716462012_thermostathousing.thumb.jpg.9d7159171751f20baf0fe01dab832818.jpg

 

-John

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