Blown Apexi head gasket?

[Dillinja666]

So I have an s13 redtop swapped into my datsun 510. The motor ran good for a couple weeks but then started having heat issues. The temp would creep up at idle but drop back down when driving on the freeway. Recently it started not dropping down when on the freeway and when I would get off the freeway temps would climb until it was pretty damn hot. At that point I found 2 pin holes in some of the original 510 hoses going to the heater core which I replaced. After replacing those I still have the heat issue. At that point I stopped driving it long distances.

Motor is a fresh rebuild with maybe 4-5K. CP pistons, eagle rods, acl bearings, arp head studs and mains with appropriate machine work, apexi head gasket, built head running stage 2 cams. Also have a walbro fuel pump but still have the stock FPR if that is needed info. New nissan thermostat and water pump is new as well.

So... head gasket? Anything else I should check before I rip this head off?

Thanks guys.

edit:
compression is 173-176 on all 4 cylinders.

[skazat]

Theres not enough info to know for sure but if your comp test was good then I doubt its your head gasket.

What have you done so far for diagnosis?

Im assuming the hoses you replaced were leaking, did you refill the radiator? If so did you purge the system for air bubbles?

[Dillinja666]

Theres not enough info to know for sure but if your comp test was good then I doubt its your head gasket.

What have you done so far for diagnosis?

Im assuming the hoses you replaced were leaking, did you refill the radiator? If so did you purge the system for air bubbles?

Yep purged it with the bleeder and a couple old school ways I know but it still overheats. I haven't driven it enough since the repair to see if it is consuming coolant because it cant stay cool. I tested the radiator by hand to see if it had cool spots in it like it was plugged but it felt fine. Both upper and lower hoses are hot so I know coolant is flowing. I'm at a loss here which is why I am turning to you guys.

I pulled the spark plugs and looking in the cylinders to see if I had a steam cleaned piston but they are all the same dirty-ness. I've even left the cap off over night seeing if I can get more coolant in the system in the morning but it remains full to the brim.

[skazat]

Are you using the factory water temp gauge? I know some people have issues where the factory dummy gauge starts acting up and showing it getting hot when its not really.

Maybe the heater core is clogged, try bypassing it and see if that works.

[Dillinja666]

Are you using the factory water temp gauge? I know some people have issues where the factory dummy gauge starts acting up and showing it getting hot when its not really.

Maybe the heater core is clogged, try bypassing it and see if that works.

Even if the heater core is blocked wouldn't the rest of the cooling system flow enough? I didn't think that would affect the block that much.

also I have the datsun 510 temp gauge in the stock cluster. I has always read the right temp with the old SR that came in car. This is the same sensor and temp was good at first when I had the new motor in for a while. It started this weird heating issue after having a couple coolant leaks and got hot a couple times.

[Dillinja666]

any other ideas?

[jr_ss]

Tested the thermostat lately? By a hydrocarbon test to verify that the head gasket is intact. I'd also check your radiator cap. If it has failed or weak it will not let the cooling system build the pressure needed to keep coolant from boiling or causing issues.

[Dillinja666]

Found the problem. Aftermarket water pump sucks. Pulled the water pump off to inspect the fins to see if there was any damage and found the fins were shaped like triangles. Looked at the nissan brand water pump on my exploded motor and found the fins were shaped like rectangles. Basically 2x the amount of contact space with water. Swapped the pump and bam.. no more over heating.

A friend of mine said he had seen the same thing before on an SR20, aftermarket water pump not moving enough water at idle to keep the motor cool.

[jr_ss]

Perfect reason to buy quality OEM parts.

[fliprayzin240sx]

What are you using for fans? I wouldn't automatically blame the water pump honestly. If its moving water, its working, specially when you're just cruising on it. Just cuz its overheating, I wouldn't automatically assume its the HG. You'd be surprised what good fan set up would do.

I had this issue with my RB, was running FAL fans as pushers and temp would creep up to 100* cruising long distances. Swapped it out for actual pusher 13" and 11" SPAL fans, temp is rock steady at 80-85 on just the 13" fan. Turn my 2nd fan on and it would drop down to 70*.

[Dillinja666]

Generic pullers. With my first motor I didn't have heat issues. This one I started having them but only at idle. Since the pump swap no issues. It was the pump.

[fliprayzin240sx]

Id still recommend you to change it. Stock fan and shroud works wonders or even upgrade GKTech fan.

[Mikester]

Id still recommend you to change it. Stock fan and shroud works wonders or even upgrade GKTech fan.

GKTech fan & stock SR shroud (if there is room for it in a 510) is not good- it's AMAZING! I laugh at the track at all the people with their hoods open trying to cool their engines... I sit there at idle with the temp stable at 70ish (read from OEM sensor after radiator) to try to keep it warm.

Personally, I say if the water pump fixed it, then no reason to throw extra duckets at it... and +1 on Glenn's perspective on quality OEM replacement parts.

[Dillinja666]

Ya there's maybe 4 to 5 inches max from the water pump to the rad. I don't think the stock fan would fit. How deep is the gktech fan?

Edit: I'm an idiot, I'm not running stock rad so stock shroud won't even come close, like 5 inches too tall. My rad is 17 inches tall.

[Mikester]

GKTech fan covers about the same depth as the OEM as it is a form/fit replacement... However, it's thinner, much lighter and moves some serious air!!!

Mine:

https://farm9.staticflickr.com/8094/8538715942_5b306f7654_c_d.jpg