Hey forum, its been a year im trying to fix my car overheating, finally i decided to overhaul whole system once again, take everything apart and test again each component, new water pump, new thermostats, recored radiator. my bad i didnt test new thermostats prior to isntalling them, and now i can see that my 2 banks are quite differ from each other in terms of temps. But biggest question is, was my radiator correctly recored. I personally have no idea how radiator looks inside and how it suppose to work, or what they could do wrong, but i hope there is a procedure to test it.

Logically i think i can tape one thermometer prob to the bottom hose and another prob to upper hose and see what the temp difference is when car is up to temp, idling and my efans are working. Is this the right way? What temp difference i should be seeing on average?
Thank you

 

Good plan. You should see at least a 10° C drop across the radiator top to bottom, fans working.

Worth checking the crossflow first.

• Drain radiator;
• remove the hoses top and bottom;
• Remove radiator and tilt it so A bank top hose inlet is upwards about 15 degrees (i e radiator upright but tilted to the left, so standing on the lower LHS corner)
• start filling up the B bank top inlet as far as you can (you will need a helper)

1. water should NOT come out of the radiator bottom outlet when the water is first entering the B bank top inlet
2. tilt it back so it is upright
3. water should now come out of the bottom outlet.

The idea of the test is to PROVE that the divider in the radiator B bank side tank that should prevent water going straight down the B bank radiator side tank is actually working. The water MUST go across to the A bank side and then down that side and back across to the outlet.

 

Thanks Greg, will do it!
Since taping probs to top and bottom hoses is a bit easier then removing rad, i did this exercise today

however this car is a damn mystery.

My efans thermoswitch is suppose to turn on at 200f and cut at 185F, and they do come up exactly when the gauge shows just a hair right to N.
At this time my probs taped to B bank top and bottom hoses showing 169F(76C) for top hose and 160F(71C) for bottom hose

However this time car did went through 4 circles of efan on/off normally.
Does that mean that rad doesnt do its job? Does it confirm that because of that while driving car overheats more then idling?

 

If the car is up to temperature, the 76°C is far too cool. I think either your thermostats are wrong or your probes must be giving inaccurate readings. Are you using a K type thermometer? If so try taping the top probe directly to the radiator at the top of the B bank side tank.

Where is the E fan thermostatic switch situated and how are the fans controlled?
Are you SURE the thermostats are long enough when open to close off the ports to the crosspipe?
Water going through the radiator too quickly is a reason for a car overheating more the faster it goes. Hence my suggestion about testing it.

 

Thanks Greg for helping me out

yes, im using K type thermometer and probs just taped to the hoses. i do beleive that 76C is not correct reading, as efans kicks in at 200f, temp gauge showing middle N, and AUX fan is on. So none of that wouldnt work at 76C. However the difference of 6c between two probes probably is correct, even if the temps are not. i will try to tape it to the top of rad. what about bottom hose? mb i should try tape it to waterpump housing?

Thermostats are Dayco DT18A which were suggested by Grant or you in sticky forum thread. (waited them a month from australia)

efan thermoswitch is situated on the place of ex air pump vacuum valve? (dont remember its name, that thing from back of water rail on A Bank ) efan (single one) connected to that thermoswitch, relay and ignition which i took from AUX fan connector .

 

Taping to the water pump inlet is a good idea.

Greg

 

Hi all! Ok it took me several rounds to measure temps at all points. Please note temps were taken with different car cycles (it was too hot to retape it on the go, given that i have only 2 probs) with car fully warmed up, efans on, around N on the gauge (but not exactly, as its not possible with different cycles)

here i put everything on diagram



Here are several clues

is 9C difference between B bank thermostat housing and water pump inlet is enough? i heard that radiator should be cooling 10-30C

Please not the difference on the A side between thermostat housing(68C) and rail where temp sensor sits (83C) , does it mean that themostat is stuck closed? For me it looks like it

it seems like it explains why car overheats more while driving, since engine warms up more and A side not passing water to radiator ?

Does my measurements make sense and explains the problem?

P.S i didnt probe back of the rails, but my thermo gun shows greater temperatures around 95C (thermo gun should be accurate, since i compared it with probs) Does it ring a bell?

Thank you

 

Stat FOR sure stick closed. WATER PUMP INLET TEMP IS ABSOLUTELY FINE.

Overheating because hot coolant on A bank is not going to the rad but straight back to the pump via the cross pipe.

Replace thermostat!

 

When i want things to be broken, they actually arent.

Removed thermostat from A bank, boiled it 5 times, 35mm closed, 44 wide open. it works as it should
im now loosing hope and any understanding

 

does this look like normal A bank water rail inside? i dont have spare one to compare, and cant find any photo on the internet, but it does look strange with this sharp and uneven shape, looks like piece missing, but mb it just like that.

 

Check to see if the disc on the stat that SHOULD seat on the flat ring of the casting and thus close off the path to the cross pipe actually can. I expect that if you look at the B bank equivalment you will see the casting is without those unmachined or somehow added extra bits

If not, either grind off those bits or get a new second hand casting.

 

If the temps you have noted on the drawing are after stabilized on a hot engine, none indicate overheating. 85c is 185f which seem pretty good to me. If I am correct, the thermostat housing picture shows recessed areas to the left and right of the bypass seat- this wouldn’t prevent correct thermostat operation.
Remind me why you think it is overheating?
Can you install your thermocouples so they are submerged in coolant at each radiator tank at the upper hose connections? I mentioned that you can get probes with 1/8NPT bushings; these will thread into the bleed plug bung and the banjo bolt bung (you will have to plug off the bleed piping). Also check your probe readings in a pot of boiling water,I have found that they sometimes have an offset from actual temperature that you must take into account when you measure your coolant temps.

 

Thank you for taking your time and trying to help me!
So, lets start with why i think car overheats, at idle in park temperature gauge goes just a bit above N and this is when my efan with thermoswitch set at 200F kicks in, this gives me an indication that both thermoswitch and gauge works correctly, then temp goes down bellow N, efan turns off. However while driving , no matter of driving style and speed gauge goes above N, efan turns on and never shuts off, as temperature keeps slooowly rising, i never let it go to the middle line between N and H

The only weird thing with temps i have noticed that back of the rails sits way hotter than front.
Also weird part is, that probes taped to rail housing next to the gauge sensor shows 83-85 , but temperature gauge is a bit above N.

i will have to buy thermo couples with 1/8 NPT to test it out.

 

See subsequent posts, I had entirely misread the photo.

 

Hi Greg, my photo mb a bit confusing, those "broken" sides are not tubes sitting above the seat, they are holes going bellow the seat. So logically they shouldnt prevent closure, at least as i see it. I was just wondering why it looks like they are broken, the "cut" on the left side of the seat is not even straight and has sharp edges like it fell off. But as i said, if you take thermostat bottom disc and place it there nothing will prevent full closure (at least from what i understand). Ofcourse i dont know if by design thermostat sit should be as full circle to be very tight, in my picture it wont be as tight as on B bank, which looks like this

 

Thanks for the explanation! Sorry I could not see the photo correctly. In any case that casting is broken and I would for sure change it for another one with an nintact sealing ring before doing anything else.
You measurements as in your excellent diagram in post no.7 above prove beyond doubt that the problem is in the casting/thermostat arrea on A bank somewhere, so I think you must fit a proper casting and then see what happens. There are lots out there, for example:
https://www.ebay.co.uk/itm/295151748...Bk9SR4CN167NYg

Another point, where are the bits that broke off!!?

Shows how much I know! I have just looked at photos of ones for sale, here:
https://www.ebay.com/itm/32542384734...Bk9SR9Lrjq_NYg
and here:
https://www.ebay.com/itm/202396113270?hash=item2f1fbf9976:gWMAAOSwpEdbX~F 7&amdata=enc%3AAQAIAAAA0EOUb%2BsbWrw13C3rfH3lkDeKH CfZJVaYyEaRiMOy8ARIm%2Ba80BRaQRZGOR0X%2BU45MPYlq%2 BJ0CM%2BkYXJnxp3pTKmHWS7cxfIOSN5EqnOVLiCeVGUkwXLmf PiWRe4huaBsU4n3tHOFL%2B2VBud0%2Fu2eEn1iKOSpRLctDaO eBpc2BKLo3G2kWb0P4Ebs7rIV9FfCKakDOgNtfa4iorbf4Az7n 97n3drKg9trVz3bkosrjUHlMrqHW0MR7%2Fz844SrbOG3aqwFB Y0Zo9B2C14OboE0yEU%3D%7Ctkp%3ABk9SR9K5_K7NYg

BOTH show the breaks in the casting that yours does! All I can suggest is that you inspect the water manifold casting very carefully and 100% ensure that there are no restrictions in it anywhere and all the coolant pathways are clear. Removing the casting is always problematic as the securing bolts shear off, so I do not suggest doing that yet, which gives further difficulties drilling them out and retapping the holes...

• Carefully measure the distance from the thermostat fixing ring point in the casting down to the ring.
• Then heat up the thermostat in a saucepan and measure it fully open to be SURE it opens far enough to close off the ring port.
• Also make 100% sure that the thermostat ring can seal without problems onto the "broken' ring and that there is nothing sticking up to prevent it; for example the thermostat ring being too large in diameter, or a bit bent or off centre, and thus getting caught on the lip above the machined ring in the casting

Finally,

• are you 100% sure your temperature difference in your post 7 diagram is accurate? If it is, the top hose should be significantly cooler to the touch on A bank than B bank.
• Also have you done the radiator side tank test?

 

My sincere apology, Sir for my original reply to your post, which I have edited. I had completely misunderstood the photo.

 

Thank you Greg, indeed all look like mine, so i can cross this one out.

yes, i did measure the distance its 42mm and did test thermostats, they open to 44mm.
Unfortunately i cant really test if thermostat ring can sit nicely in the rail, as it should be expanded and even then you cant really see it.

i will recheck all temperatures once again! Thank you

 

I wonder if the temperature at the rear of the rail is a red herring. Normally, the electric cooling fan control sensor is located either by the thermostat or in the radiator outlet/water pump inlet (which is where Jaguar put the condenser fan sensor). Makes sense as you would only want the fan to run when insufficient air flow through the radiator is indicated by a rise in the radiator outlet temp.
Perhaps the temperature at the rear of the water rail is normally higher and is why your e-fan stays on. And maybe the fan running interferes with airflow through the radiator when normal vehicle movement is causing otherwise sufficient airflow. Just a thought…..
Putting probes in both radiator tanks at the upper hoses will tell the tale. If the temps there seem normal, I would pull the water rails and see if anything is restricted, if not, relocate your fan sensor (or use the OE location at the water pump inlet).

 

There was a guy named Norman Lutz who was racing the V12; he had a modification where he installed restrictions in the water rail to even out the coolant flow. The smaller restrictors were in the front and the rear were fully open, which indicates to me that he found the rear ran hotter.
Also, do you have a heater in the vehicle? If not, don’t cap off the hoses, puta loop in place of the core.
Also, do you have a shroud on your e-fan? If so, it should have flaps that open from vehicle movement and close from fan suction. Look at the OE auxiliary fan shroud to see how they are supposed to work.