What are M20 Water Pump Options ??

[WhyNot]

hi,
i have a 91 vert M20.
i looked but didnt find anything on any high volume water pump [like Stewards make for E36, etc.] for the M20 motor.
so my questions are;;
1. are there high volume water pumps available?
2. are there different impeller designs that work better than stock?
3. if there are no options, are all stock water pumps the same?
thanks for the replies.
i hate when the temp guage goes past half way and i live in the desert and in traffic with the ac on the temps climb pretty quickly.
plus the ac craps out when it gets too hot.
thanks for the advice and help

[idanity]

they're not all the same;
but the tensioner is what has been improved upon...

i replace my h20pump every time i do a timing belt, and have always used a dealership part.
i also tried to search for an 'improved' one, like the e36's or other models that are known to be made from plastic, not metal..but i assure you, the dealer one is all metal, and also garunteed...just replace the timing belt, and tensioner at the same time.

fairly certain its a graf brand.

[5Toes]

Some have impellers like this one attached

Others like this:



Not sure which is better

[idanity]

if you replace them every 4 years, i don't think it would matter, as i have seen some OEM types last over ten years, and still worked until the timing belt snapped.

the biggest problem was the tensioners, and people not running proper coolant. (or neglecting the t.b.)

[e30leigh]

just buy a genuine bmw pump and you wont have any issues.

as for the pics. the 1st one looks to be oem. while the other looks a cheeper option. the increased number of impellers on the first one would provide faster and higher volume of water flow.

[jlevie]

It sounds to me like you have a cooling system problem. The day I charged the A/C in my restoration project out side air temperature was 102F. I was charging the system in the garage and the temperature there climbed to 110F during the procedure. The engine ran at a fast idle for close to an hour in those conditions with the A/C running and the gauge needle didn't even reach the half way mark.

The gauge isn't necessarily the most accurate indication. I knew the conditions would be extreme and was monitoring head temperature with an IR thermometer that I know to be pretty accurate. Steady state temperature of the engine at the beginning was 178F, which is right for an 80C thermostat. The highest I saw was 196F, not even high enough to cause the aux fan to go to high speed (210-212F). As a point of comparison, my race car in the similar conditions doesn't see above 198F. It doesn't have A/C, but it is running at full throttle most of the time and thus generating a lot of heat.

It has been a bit cooler since then (temps up to 97F) and gauge needle has never gotten above the half way point at any point while driving. The needle normally sits about 1/4 of the way between the fist tic mark and the half way mark.

Slightly higher temperatures can be seen briefly when driving. That will occur when the car is idling or moving very slowly immediately after extended highway speed driving. In that case there is quite a bit of stored heat in the engine and the lower air flow and coolant circulation will spike the temperature slightly, perhaps up to 210-215F. But if the cooling system is working properly the temperature will come back down quickly.

This project car, being a restoration, has a freshly rebuilt engine and all parts of the cooling system are new (radiator, hoses, water pump, thermostat, fan clutch, aux fan, expansion tank, and cap). Because you can't hot tank an M20 engine (that will destroy the intermediate shaft bearings) I flushed the cooling immediately after the rebuild to clean any deposits or trash out of the block. For that I started with a detergent type flush to clean any oil or grease and then used oxalic acid to remove lime scale and rust. I kept the old radiator in until the flush was complete.

So if everything is right there is no need for a higher volume pump. In this case I'd flush the cooling system, replace the radiator, fan clutch, and thermostat, and make sure that the aux fan is operating properly. Because most, if not all, of the other parts of the cooling system are probably ten years old or older I'd replace all hoses, the expansion tank & cap, and the water pump.

[SkiFree]

From the technical side of things I agree with Jlevie.


As for the differences in the different brands available, what's already said is a bit incomplete. 5toes, the water pump you've pictured on top looks to be GRAF pump (and if I'm not mistaken, from the IE website), the pump on bottom is the GMB pump.

Brands:

Hepu: Good (carousel style impeller)
GMB: OK (fan syle impeller)
Graf: Good (carousel style impeller)
Meyle: OK (carousel style impeller)
Laso: Good (carousel style impeller)
OEM (Saleri): OK ("composite [plastic] impeller")

Keep in mind that availability constantly fluctuates on all these (which is why most of us resellers don't list a brand). I like to keep Graf and Hepu on the shelf, but sometimes have to substitute a Meyle (customers of just about any reseller/shop can always call to specify a preference). The ONLY ones I've seen fail to with any degree of consistency is obviously the pumps with the plastic impeller. ALL OTHER pumps function relatively well and shouldn't be cause for any catastrophic engine failures.

If you want to get REALLY technical the fan-style impeller does not push quite as much as a carousel-style impeller, but at that stage you're really splitting hairs and it's MUCH more likely your cause for overheating is something (anything) else.

[WhyNot]

thanks for the detailed replies, i really appreciate the time & effort.
there was good info that i use and maybe someone else can benefit too.

here's the thermostat

so now its cooler and has quite a bit more power since its not running hot and its flowing though the system.
used a china 176F.
if anyone is gonna change the thermostat, do yourself a favor and get a new cover [it is not a thermostat housing] AND a new bleed screw.
my 30 min job is taking 3 days just dealing with parts.

my radiator is original and has few wet spots that dont leak under pressure.
im trying to see if a e36 z3 with side tank fits but the info is mostly for swaps.
cheers & thanks again.
whynot